1
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Bird JP, Fuller RA, Shaw JD. Patterns of recovery in extant and extirpated seabirds after the world's largest multipredator eradication. Conserv Biol 2024:e14239. [PMID: 38375602 DOI: 10.1111/cobi.14239] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/28/2023] [Revised: 11/27/2023] [Accepted: 12/02/2023] [Indexed: 02/21/2024]
Abstract
Eradicating invasive predators from islands can result in substantial recovery of seabirds, but the mechanisms that drive population changes remain poorly understood. Meta-analyses have recently revealed that immigration is surprisingly important to the recovery of philopatric seabirds, but it is not known whether dispersal and philopatry interact predictably to determine rates of population growth and changes of distribution. We used whole-island surveys and long-term monitoring plots to study the abundance, distribution, and trends of 4 burrowing seabird species on Macquarie Island, Australia, to examine the legacy impacts of invasive species and ongoing responses to the world's largest eradication of multiple species of vertebrates. Wekas (Gallirallus australis) were eradicated in 1988; cats (Felis catus) in 2001; and rabbits (Oryctolagus cuniculus), black rats (Rattus rattus), and mice (Mus mus) in 2011-2014. We compared surveys from 1976-1979 and 2017-2018 and monitoring from the 1990s and 2000s onward. Antarctic prions (Pachyptila desolata) and white-headed petrels (Pterodroma lessonii) increased ∼1% per year. Blue petrels (Halobaena caerulea) and gray petrels (Procellaria cinerea) recolonized following extirpation from the main island in the 1900s but remained spatially and numerically rare in 2018. However, they increased rapidly at 14% and 10% per year, respectively, since cat eradication in 2001. Blue and gray petrel recolonization occurred on steep, dry, west-facing slopes close to ridgelines at low elevation (i.e., high-quality petrel habitat). They overlapped <5% with the distribution of Antarctic prion and white-headed petrels which occurred in suboptimal shallow, wet, east-facing slopes at high elevation. We inferred that the speed of population growth of recolonizing species was related to their numerically smaller starting size compared with the established species and was driven by immigration and selection of ideal habitat.
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Affiliation(s)
- Jeremy P Bird
- School of Biological Sciences, The University of Queensland, St Lucia, Queensland, Australia
| | - Richard A Fuller
- School of Biological Sciences, The University of Queensland, St Lucia, Queensland, Australia
| | - Justine D Shaw
- School of Biological Sciences, The University of Queensland, St Lucia, Queensland, Australia
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2
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McInnes JC, Bird JP, Deagle BE, Polanowski AM, Shaw JD. Using
DNA
metabarcoding to detect burrowing seabirds in a remote landscape. Conservat Sci and Prac 2021. [DOI: 10.1111/csp2.439] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
Affiliation(s)
- Julie C. McInnes
- Institute for Marine and Antarctic Studies University of Tasmania Battery Point Tasmania Australia
- Australian Antarctic Division Department of Agriculture, Water and the Environment Kingston Tasmania Australia
| | - Jeremy P. Bird
- Institute for Marine and Antarctic Studies University of Tasmania Battery Point Tasmania Australia
- School of Biological Sciences The University of Queensland St Lucia Queensland Australia
| | - Bruce E. Deagle
- Australian Antarctic Division Department of Agriculture, Water and the Environment Kingston Tasmania Australia
- Commonwealth Scientific and Industrial Research Organisation Battery Point Tasmania Australia
| | - Andrea M. Polanowski
- Australian Antarctic Division Department of Agriculture, Water and the Environment Kingston Tasmania Australia
| | - Justine D. Shaw
- School of Biological Sciences The University of Queensland St Lucia Queensland Australia
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3
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Arabchigavkani N, Somphonsane R, Ramamoorthy H, He G, Nathawat J, Yin S, Barut B, He K, Randle MD, Dixit R, Sakanashi K, Aoki N, Zhang K, Wang L, Mei WN, Dowben PA, Fransson J, Bird JP. Remote Mesoscopic Signatures of Induced Magnetic Texture in Graphene. Phys Rev Lett 2021; 126:086802. [PMID: 33709762 DOI: 10.1103/physrevlett.126.086802] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/15/2020] [Accepted: 01/19/2021] [Indexed: 06/12/2023]
Abstract
Mesoscopic conductance fluctuations are a ubiquitous signature of phase-coherent transport in small conductors, exhibiting universal character independent of system details. In this Letter, however, we demonstrate a pronounced breakdown of this universality, due to the interplay of local and remote phenomena in transport. Our experiments are performed in a graphene-based interaction-detection geometry, in which an artificial magnetic texture is induced in the graphene layer by covering a portion of it with a micromagnet. When probing conduction at some distance from this region, the strong influence of remote factors is manifested through the appearance of giant conductance fluctuations, with amplitude much larger than e^{2}/h. This violation of one of the fundamental tenets of mesoscopic physics dramatically demonstrates how local considerations can be overwhelmed by remote signatures in phase-coherent conductors.
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Affiliation(s)
- N Arabchigavkani
- Department of Physics, University at Buffalo, the State University of New York, Buffalo, New York 14260, USA
| | - R Somphonsane
- Department of Physics, King Mongkut's Institute of Technology Ladkrabang, Bangkok 10520, Thailand
| | - H Ramamoorthy
- Department of Electronics Engineering, King Mongkut's Institute of Technology Ladkrabang, Bangkok 10520, Thailand
| | - G He
- Department of Electrical Engineering, University at Buffalo, the State University of New York, Buffalo, New York 14260, USA
| | - J Nathawat
- Department of Electrical Engineering, University at Buffalo, the State University of New York, Buffalo, New York 14260, USA
| | - S Yin
- Department of Electrical Engineering, University at Buffalo, the State University of New York, Buffalo, New York 14260, USA
| | - B Barut
- Department of Physics, University at Buffalo, the State University of New York, Buffalo, New York 14260, USA
| | - K He
- Department of Electrical Engineering, University at Buffalo, the State University of New York, Buffalo, New York 14260, USA
| | - M D Randle
- Department of Electrical Engineering, University at Buffalo, the State University of New York, Buffalo, New York 14260, USA
| | - R Dixit
- Department of Electrical Engineering, University at Buffalo, the State University of New York, Buffalo, New York 14260, USA
| | - K Sakanashi
- Department of Materials Science, Chiba University, Chiba 263-8522, Japan
| | - N Aoki
- Department of Materials Science, Chiba University, Chiba 263-8522, Japan
| | - K Zhang
- Department of Materials Science and Engineering, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - L Wang
- Department of Materials Science and Engineering, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - W-N Mei
- Department of Physics, University of Nebraska Omaha, Omaha, Nebraska 68182, USA
| | - P A Dowben
- Department of Physics and Astronomy, Theodore Jorgensen Hall, University of Nebraska Lincoln, Lincoln, Nebraska 68588-0299, USA
| | - J Fransson
- Department of Physics and Astronomy, Uppsala University, Box 516, SE-751 21 Uppsala, Sweden
| | - J P Bird
- Department of Electrical Engineering, University at Buffalo, the State University of New York, Buffalo, New York 14260, USA
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4
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Mavea WB, Belonovich O, Nagombi E, Boslogo T, Gwynn L, Russ R, Bird JP. A survey of cetaceans in New Britain, Papua New Guinea. Aust Mammalogy 2021. [DOI: 10.1071/am21005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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5
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Bird JP, Martin R, Akçakaya HR, Gilroy J, Burfield IJ, Garnett ST, Symes A, Taylor J, Şekercioğlu ÇH, Butchart SHM. Generation lengths of the world's birds and their implications for extinction risk. Conserv Biol 2020; 34:1252-1261. [PMID: 32058610 DOI: 10.1111/cobi.13486] [Citation(s) in RCA: 75] [Impact Index Per Article: 18.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/31/2019] [Revised: 02/05/2020] [Accepted: 02/10/2020] [Indexed: 06/10/2023]
Abstract
Birds have been comprehensively assessed on the International Union for Conservation of Nature (IUCN) Red List more times than any other taxonomic group. However, to date, generation lengths have not been systematically estimated to scale population trends when undertaking assessments, as required by the criteria of the IUCN Red List. We compiled information from major databases of published life-history and trait data for all birds and imputed missing life-history data as a function of species traits with generalized linear mixed models. Generation lengths were derived for all species, based on our modeled values of age at first breeding, maximum longevity, and annual adult survival. The resulting generation lengths varied from 1.42 to 27.87 years (median 2.99). Most species (61%) had generation lengths <3.33 years, meaning that the period of 3 generations-over which population declines are assessed under criterion A-was <10 years, which is the value used for IUCN Red List assessments of species with short generation times. For these species, our trait-informed estimates of generation length suggested that 10 years is a robust precautionary value for threat assessment. In other cases, however, for whole families, genera, or individual species, generation length had a substantial impact on their estimated extinction risk, resulting in higher extinction risk in long-lived species than in short-lived species. Although our approach effectively addressed data gaps, generation lengths for some species may have been underestimated due to a paucity of life-history data. Overall, our results will strengthen future extinction-risk assessments and augment key databases of avian life-history and trait data.
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Affiliation(s)
- Jeremy P Bird
- BirdLife International, David Attenborough Building, Pembroke Street, Cambridge, CB2 3QZ, U.K
- Centre for Biodiversity and Conservation Science, University of Queensland, St Lucia, QLD 4072, Australia
| | - Robert Martin
- BirdLife International, David Attenborough Building, Pembroke Street, Cambridge, CB2 3QZ, U.K
| | - H Reşit Akçakaya
- Department of Ecology and Evolution, Stony Brook University, 100 Nicolls Road, Stony Brook, NY, 11794, U.S.A
- IUCN Species Survival Commission, IUCN, Rue Mauverney 28, Gland, 1196, Switzerland
| | - James Gilroy
- School of Environmental Sciences, University of East Anglia, Norwich, NR4 7TJ, U.K
| | - Ian J Burfield
- BirdLife International, David Attenborough Building, Pembroke Street, Cambridge, CB2 3QZ, U.K
| | - Stephen T Garnett
- Research Institute for the Environment and Livelihoods, Charles Darwin University, Casuarina, Darwin, Northern Territory, 0909, Australia
| | - Andy Symes
- BirdLife International, David Attenborough Building, Pembroke Street, Cambridge, CB2 3QZ, U.K
| | - Joseph Taylor
- BirdLife International, David Attenborough Building, Pembroke Street, Cambridge, CB2 3QZ, U.K
| | - Çağan H Şekercioğlu
- School of Biological Sciences, University of Utah, 257 S 1400 E, Salt Lake City, UT, 84112, U.S.A
- Department of Molecular Biology and Genetics, Koç University, Istanbul, Turkey
- KuzeyDoğa Derneği, Ortakapı Mah. Şehit Yusuf Bey Cad. No: 93 Kars, Turkey
- Department of Zoology, University of Cambridge, Downing Street, Cambridge, CB2 3EJ, U.K
| | - Stuart H M Butchart
- BirdLife International, David Attenborough Building, Pembroke Street, Cambridge, CB2 3QZ, U.K
- Department of Zoology, University of Cambridge, Downing Street, Cambridge, CB2 3EJ, U.K
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6
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Somphonsane R, Ramamoorthy H, He G, Nathawat J, Yin S, Kwan CP, Arabchigavkani N, Barut B, Zhao M, Jin Z, Fransson J, Bird JP. Universal scaling of weak localization in graphene due to bias-induced dispersion decoherence. Sci Rep 2020; 10:5611. [PMID: 32221340 PMCID: PMC7101405 DOI: 10.1038/s41598-020-62313-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2019] [Accepted: 03/11/2020] [Indexed: 11/29/2022] Open
Abstract
The differential conductance of graphene is shown to exhibit a zero-bias anomaly at low temperatures, arising from a suppression of the quantum corrections due to weak localization and electron interactions. A simple rescaling of these data, free of any adjustable parameters, shows that this anomaly exhibits a universal, temperature- (T) independent form. According to this, the differential conductance is approximately constant at small voltages (V < kBT/e), while at larger voltages it increases logarithmically with the applied bias. For theoretical insight into the origins of this behaviour, which is inconsistent with electron heating, we formulate a model for weak-localization in the presence of nonequilibrium transport. According to this model, the applied voltage causes unavoidable dispersion decoherence, which arises as diffusing electron partial waves, with a spread of energies defined by the value of the applied voltage, gradually decohere with one another as they diffuse through the system. The decoherence yields a universal scaling of the conductance as a function of eV/kBT, with a logarithmic variation for eV/kBT > 1, variations in accordance with the results of experiment. Our theoretical description of nonequilibrium transport in the presence of this source of decoherence exhibits strong similarities with the results of experiment, including the aforementioned rescaling of the conductance and its logarithmic variation as a function of the applied voltage.
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Affiliation(s)
- R Somphonsane
- Department of Physics, King Mongkut's Institute of Technology Ladkrabang, Bangkok, 10520, Thailand.
- Thailand Center of Excellence in Physics, Commission on Higher Education, 328 Si Ayutthaya Road, Bangkok, 10400, Thailand.
| | - H Ramamoorthy
- Department of Electronic Engineering, King Mongkut's Institute of Technology Ladkrabang, Bangkok, 10520, Thailand
| | - G He
- Department of Electrical Engineering, University at Buffalo, The State University of New York, Buffalo, NY, 14260-1900, USA
| | - J Nathawat
- Department of Electrical Engineering, University at Buffalo, The State University of New York, Buffalo, NY, 14260-1900, USA
| | - S Yin
- Department of Electrical Engineering, University at Buffalo, The State University of New York, Buffalo, NY, 14260-1900, USA
| | - C-P Kwan
- Department of Physics, University at Buffalo, The State University of New York, Buffalo, NY, 14260-1500, USA
| | - N Arabchigavkani
- Department of Physics, University at Buffalo, The State University of New York, Buffalo, NY, 14260-1500, USA
| | - B Barut
- Department of Physics, University at Buffalo, The State University of New York, Buffalo, NY, 14260-1500, USA
| | - M Zhao
- High-Frequency High-Voltage Device and Integrated Circuits Center, Institute of Microelectronics of Chinese Academy of Sciences, 3 Beitucheng West Road, Chaoyang District, Beijing, PR China
| | - Z Jin
- High-Frequency High-Voltage Device and Integrated Circuits Center, Institute of Microelectronics of Chinese Academy of Sciences, 3 Beitucheng West Road, Chaoyang District, Beijing, PR China
| | - J Fransson
- Department of Physics and Astronomy, Uppsala University, Box 516, SE-751 21, Uppsala, Sweden
| | - J P Bird
- Department of Electrical Engineering, University at Buffalo, The State University of New York, Buffalo, NY, 14260-1900, USA
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7
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Lee YH, Xiao S, Kim KW, Reno JL, Bird JP, Han JE. Giant Zero Bias Anomaly due to Coherent Scattering from Frozen Phonon Disorder in Quantum Point Contacts. Phys Rev Lett 2019; 123:056802. [PMID: 31491285 DOI: 10.1103/physrevlett.123.056802] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/12/2018] [Revised: 04/26/2019] [Indexed: 06/10/2023]
Abstract
We demonstrate an unusual manifestation of coherent scattering for electron waves in mesoscopic quantum point contacts, in which fast electron dynamics allows the phonon system to serve as a quasistatic source of disorder. The low-temperature conductance of these devices exhibits a giant (≫2e^{2}/h) zero bias anomaly (ZBA), the features of which are reproduced in a nonequilibrium model for coherent scattering from the "frozen" phonon disorder. According to this model, the ZBA is understood to result from the in situ electrical manipulation of the phonon disorder, a mechanism that could open up a pathway to the on-demand control of coherent scattering in the solid state.
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Affiliation(s)
- Y-H Lee
- Department of Electrical Engineering, University at Buffalo, the State University of New York, Buffalo, New York 14260, USA
| | - S Xiao
- Department of Electrical Engineering, University at Buffalo, the State University of New York, Buffalo, New York 14260, USA
| | - K W Kim
- Center for Theoretical Physics of Complex Systems, Institute for Basic Science (IBS), Daejeon 34126, Republic of Korea
| | - J L Reno
- CINT, Sandia National Laboratories, Department 1881, MS 1303, Albuquerque, New Mexico 87185, USA
| | - J P Bird
- Department of Electrical Engineering, University at Buffalo, the State University of New York, Buffalo, New York 14260, USA
| | - J E Han
- Department of Physics, University at Buffalo, the State University of New York, Buffalo, New York 14260, USA
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8
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He G, Ramamoorthy H, Kwan CP, Lee YH, Nathawat J, Somphonsane R, Matsunaga M, Higuchi A, Yamanaka T, Aoki N, Gong Y, Zhang X, Vajtai R, Ajayan PM, Bird JP. Thermally Assisted Nonvolatile Memory in Monolayer MoS 2 Transistors. Nano Lett 2016; 16:6445-6451. [PMID: 27680095 DOI: 10.1021/acs.nanolett.6b02905] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
We demonstrate a novel form of thermally-assisted hysteresis in the transfer curves of monolayer MoS2 FETs, characterized by the appearance of a large gate-voltage window and distinct current levels that differ by a factor of ∼102. The hysteresis emerges for temperatures in excess of 400 K and, from studies in which the gate-voltage sweep parameters are varied, appears to be related to charge injection into the SiO2 gate dielectric. The thermally-assisted memory is strongly suppressed in equivalent measurements performed on bilayer transistors, suggesting that weak screening in the monolayer system plays a vital role in generating its strongly sensitive response to the charge-injection process. By exploiting the full features of the hysteretic transfer curves, programmable memory operation is demonstrated. The essential principles demonstrated here point the way to a new class of thermally assisted memories based on atomically thin two-dimensional semiconductors.
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Affiliation(s)
- G He
- Department of Electrical Engineering, University at Buffalo, The State University of New York , Buffalo, New York 14260-1900, United States
| | - H Ramamoorthy
- Department of Electrical Engineering, University at Buffalo, The State University of New York , Buffalo, New York 14260-1900, United States
| | - C-P Kwan
- Department of Physics, University at Buffalo, The State University of New York , Buffalo, New York 14260-1500, United States
| | - Y-H Lee
- Department of Electrical Engineering, University at Buffalo, The State University of New York , Buffalo, New York 14260-1900, United States
| | - J Nathawat
- Department of Electrical Engineering, University at Buffalo, The State University of New York , Buffalo, New York 14260-1900, United States
| | - R Somphonsane
- Department of Physics, King Mongkut's Institute of Technology Ladkrabang , Bangkok 10520, Thailand
| | - M Matsunaga
- Graduate School of Advanced Integration Science, Chiba University , 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522, Japan
| | - A Higuchi
- Graduate School of Advanced Integration Science, Chiba University , 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522, Japan
| | - T Yamanaka
- Graduate School of Advanced Integration Science, Chiba University , 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522, Japan
| | - N Aoki
- Graduate School of Advanced Integration Science, Chiba University , 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522, Japan
| | - Y Gong
- Department of Materials Science and NanoEngineering, Rice University , Houston, Texas 77005, United States
| | - X Zhang
- Department of Materials Science and NanoEngineering, Rice University , Houston, Texas 77005, United States
| | - R Vajtai
- Department of Materials Science and NanoEngineering, Rice University , Houston, Texas 77005, United States
| | - P M Ajayan
- Department of Materials Science and NanoEngineering, Rice University , Houston, Texas 77005, United States
| | - J P Bird
- Department of Electrical Engineering, University at Buffalo, The State University of New York , Buffalo, New York 14260-1900, United States
- Graduate School of Advanced Integration Science, Chiba University , 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522, Japan
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9
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Ramamoorthy H, Somphonsane R, Radice J, He G, Kwan CP, Bird JP. Correction to "Freeing" Graphene from Its Substrate: Observing Intrinsic Velocity Saturation with Rapid Electrical Pulsing. Nano Lett 2016; 16:1514. [PMID: 26807871 DOI: 10.1021/acs.nanolett.6b00287] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
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10
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Ramamoorthy H, Somphonsane R, Radice J, He G, Kwan CP, Bird JP. "Freeing" Graphene from Its Substrate: Observing Intrinsic Velocity Saturation with Rapid Electrical Pulsing. Nano Lett 2016; 16:399-403. [PMID: 26649478 DOI: 10.1021/acs.nanolett.5b04003] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Rapid (nanosecond-scale) electrical pulsing is used to study drift-velocity saturation in graphene field-effect devices. In these experiments, high-field pulses are utilized to drive graphene's carriers on time scales much faster than that on which energy loss to the underlying substrate can occur, thereby allowing the observation of the highest saturation velocities reported to date. In a dramatic departure from the behavior exhibited by conventional metals and semiconductors, as the electron or hole density is reduced toward the charge-neutrality point, the drift velocity is found to reach values comparable to the Fermi velocity itself. Corresponding current densities are as large as 10(9) A/cm(2), similar to the values reported for carbon nanotubes and for graphene-on-diamond transistors. In essence, our approach of rapid pulsing allows us to "free" graphene from the deleterious influence of its substrate, revealing a pathway to achieve the superior electrical performance promised by this material. The usefulness of this approach is not merely limited to graphene but should extend also to a broad variety of two-dimensional semiconductors.
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Affiliation(s)
- H Ramamoorthy
- Department of Electrical Engineering, University at Buffalo, the State University of New York , Buffalo, New York 14260-1900, United States
| | - R Somphonsane
- Department of Physics, King Mongkut's Institute of Technology Ladkrabang , Bangkok 10520, Thailand
| | - J Radice
- Department of Electrical Engineering, University at Buffalo, the State University of New York , Buffalo, New York 14260-1900, United States
| | - G He
- Department of Electrical Engineering, University at Buffalo, the State University of New York , Buffalo, New York 14260-1900, United States
| | - C-P Kwan
- Department of Physics, University at Buffalo, the State University of New York , Buffalo, New York 14260-1500, United States
| | - J P Bird
- Department of Electrical Engineering, University at Buffalo, the State University of New York , Buffalo, New York 14260-1900, United States
- Graduate School of Advanced Integration Science, Chiba University , 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522, Japan
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11
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Abstract
This report on progress explores recent advances in our theoretical and experimental understanding of the physics of open quantum systems (OQSs). The study of such systems represents a core problem in modern physics that has evolved to assume an unprecedented interdisciplinary character. OQSs consist of some localized, microscopic, region that is coupled to an external environment by means of an appropriate interaction. Examples of such systems may be found in numerous areas of physics, including atomic and nuclear physics, photonics, biophysics, and mesoscopic physics. It is the latter area that provides the main focus of this review, an emphasis that is driven by the capacity that exists to subject mesoscopic devices to unprecedented control. We thus provide a detailed discussion of the behavior of mesoscopic devices (and other OQSs) in terms of the projection-operator formalism, according to which the system under study is considered to be comprised of a localized region (Q), embedded into a well-defined environment (P) of scattering wavefunctions (with Q + P = 1). The Q subspace must be treated using the concepts of non-Hermitian physics, and of particular interest here is: the capacity of the environment to mediate a coupling between the different states of Q; the role played by the presence of exceptional points (EPs) in the spectra of OQSs; the influence of EPs on the rigidity of the wavefunction phases, and; the ability of EPs to initiate a dynamical phase transition (DPT). EPs are singular points in the continuum, at which two resonance states coalesce, that is where they exhibit a non-avoided crossing. DPTs occur when the quantum dynamics of the open system causes transitions between non-analytically connected states, as a function of some external control parameter. Much like conventional phase transitions, the behavior of the system on one side of the DPT does not serve as a reliable indicator of that on the other. In addition to discussing experiments on mesoscopic quantum point contacts that provide evidence of the environmentally-mediated coupling of quantum states, we also review manifestations of DPTs in mesoscopic devices and other systems. These experiments include observations of resonance-trapping behavior in microwave cavities and open quantum dots, phase lapses in tunneling through single-electron transistors, and spin swapping in atomic ensembles. Other possible manifestations of this phenomenon are presented, including various superradiant phenomena in low-dimensional semiconductors. From these discussions a generic picture of OQSs emerges in which the environmentally-mediated coupling between different quantum states plays a critical role in governing the system behavior. The ability to control or manipulate this interaction may even lead to new applications in photonics and electronics.
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Affiliation(s)
- I Rotter
- Max Planck Institute for the Physics of Complex Systems, D-01187 Dresden, Germany
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12
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He G, Ghosh K, Singisetti U, Ramamoorthy H, Somphonsane R, Bohra G, Matsunaga M, Higuchi A, Aoki N, Najmaei S, Gong Y, Zhang X, Vajtai R, Ajayan PM, Bird JP. Conduction Mechanisms in CVD-Grown Monolayer MoS2 Transistors: From Variable-Range Hopping to Velocity Saturation. Nano Lett 2015; 15:5052-8. [PMID: 26121164 DOI: 10.1021/acs.nanolett.5b01159] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
We fabricate transistors from chemical vapor deposition-grown monolayer MoS2 crystals and demonstrate excellent current saturation at large drain voltages (Vd). The low-field characteristics of these devices indicate that the electron mobility is likely limited by scattering from charged impurities. The current-voltage characteristics exhibit variable range hopping at low Vd and evidence of velocity saturation at higher Vd. This work confirms the excellent potential of MoS2 as a possible channel-replacement material and highlights the role of multiple transport phenomena in governing its transistor action.
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Affiliation(s)
- G He
- †Department of Electrical Engineering, University at Buffalo, The State University of New York, Buffalo, New York 14260-1900, United States
| | - K Ghosh
- †Department of Electrical Engineering, University at Buffalo, The State University of New York, Buffalo, New York 14260-1900, United States
| | - U Singisetti
- †Department of Electrical Engineering, University at Buffalo, The State University of New York, Buffalo, New York 14260-1900, United States
| | - H Ramamoorthy
- †Department of Electrical Engineering, University at Buffalo, The State University of New York, Buffalo, New York 14260-1900, United States
| | - R Somphonsane
- ‡Department of Physics, King Mongkut's Institute of Technology Ladkrabang, Bangkok 10520, Thailand
| | - G Bohra
- †Department of Electrical Engineering, University at Buffalo, The State University of New York, Buffalo, New York 14260-1900, United States
| | - M Matsunaga
- §Graduate School of Advanced Integration Science, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522, Japan
| | - A Higuchi
- §Graduate School of Advanced Integration Science, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522, Japan
| | - N Aoki
- §Graduate School of Advanced Integration Science, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522, Japan
| | - S Najmaei
- ∥Department of Materials Science and NanoEngineering, Rice University, Houston, Texas 77005, United States
| | - Y Gong
- ∥Department of Materials Science and NanoEngineering, Rice University, Houston, Texas 77005, United States
| | - X Zhang
- ∥Department of Materials Science and NanoEngineering, Rice University, Houston, Texas 77005, United States
| | - R Vajtai
- ∥Department of Materials Science and NanoEngineering, Rice University, Houston, Texas 77005, United States
| | - P M Ajayan
- ∥Department of Materials Science and NanoEngineering, Rice University, Houston, Texas 77005, United States
| | - J P Bird
- †Department of Electrical Engineering, University at Buffalo, The State University of New York, Buffalo, New York 14260-1900, United States
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Xiang S, Fuji K, Sato S, Xiao S, Bird JP, Aoki N, Ochiai Y. Metal-insulator transition in the quasi-one-dimensional transport of fractional quantum Hall states. J Phys Condens Matter 2015; 27:202201. [PMID: 25920938 DOI: 10.1088/0953-8984/27/20/202201] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
We investigate edge state transmission in quantum point contacts (QPCs) in the fractional quantum-Hall regime, finding behavior reminiscent of a metal-insulator transition. The transition is suggested by an unusual behavior of the differential conductance in the fractional-quantum-Hall regime, and by the presence of a fixed point and universal scaling in the temperature dependence of the linear conductance. Noting that the 0.7 feature evolves continuously into a last fractional plateau at high magnetic fields, we suggest that this still unresolved feature may itself be viewed as a manifestation of a local, microscopic, metal-insulator transition.
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Affiliation(s)
- S Xiang
- Graduate School of Advanced Integration Science, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522, Japan
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Dawson J, Oppel S, Cuthbert RJ, Holmes N, Bird JP, Butchart SHM, Spatz DR, Tershy B. Prioritizing islands for the eradication of invasive vertebrates in the United Kingdom overseas territories. Conserv Biol 2015; 29:143-153. [PMID: 25163543 DOI: 10.1111/cobi.12347] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/19/2013] [Accepted: 04/17/2014] [Indexed: 06/03/2023]
Abstract
Invasive alien species are one of the primary threats to native biodiversity on islands worldwide. Consequently, eradicating invasive species from islands has become a mainstream conservation practice. Deciding which islands have the highest priority for eradication is of strategic importance to allocate limited resources to achieve maximum conservation benefit. Previous island prioritizations focused either on a narrow set of native species or on a small geographic area. We devised a prioritization approach that incorporates all threatened native terrestrial vertebrates and all invasive terrestrial vertebrates occurring on 11 U.K. overseas territories, which comprise over 2000 islands ranging from the sub-Antarctic to the tropics. Our approach includes eradication feasibility and distinguishes between the potential and realistic conservation value of an eradication, which reflects the benefit that would accrue following eradication of either all invasive species or only those species for which eradication techniques currently exist. We identified the top 25 priority islands for invasive species eradication that together would benefit extant populations of 155 native species including 45 globally threatened species. The 5 most valuable islands included the 2 World Heritage islands Gough (South Atlantic) and Henderson (South Pacific) that feature unique seabird colonies, and Anegada, Little Cayman, and Guana Island in the Caribbean that feature a unique reptile fauna. This prioritization can be rapidly repeated if new information or techniques become available, and the approach could be replicated elsewhere in the world.
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Affiliation(s)
- Jeffrey Dawson
- RSPB Centre for Conservation Science, Royal Society for the Protection of Birds, The Lodge, Sandy, Bedfordshire, SG19 2DL, United Kingdom
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15
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Xiang S, Xiao S, Fuji K, Shibuya K, Endo T, Yumoto N, Morimoto T, Aoki N, Bird JP, Ochiai Y. On the zero-bias anomaly and Kondo physics in quantum point contacts near pinch-off. J Phys Condens Matter 2014; 26:125304. [PMID: 24599094 DOI: 10.1088/0953-8984/26/12/125304] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
We investigate the linear and non-linear conductance of quantum point contacts (QPCs), in the region near pinch-off where Kondo physics has previously been connected to the appearance of the 0.7 feature. In studies of seven different QPCs, fabricated in the same high-mobility GaAs/AlGaAs heterojunction, the linear conductance is widely found to show the presence of the 0.7 feature. The differential conductance, on the other hand, does not generally exhibit the zero-bias anomaly (ZBA) that has been proposed to indicate the Kondo effect. Indeed, even in the small subset of QPCs found to exhibit such an anomaly, the linear conductance does not always follow the universal temperature-dependent scaling behavior expected for the Kondo effect. Taken collectively, our observations demonstrate that, unlike the 0.7 feature, the ZBA is not a generic feature of low-temperature QPC conduction. We furthermore conclude that the mere observation of the ZBA alone is insufficient evidence for concluding that Kondo physics is active. While we do not rule out the possibility that the Kondo effect may occur in QPCs, our results appear to indicate that its observation requires a very strict set of conditions to be satisfied. This should be contrasted with the case of the 0.7 feature, which has been apparent since the earliest experimental investigations of QPC transport.
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Affiliation(s)
- S Xiang
- Graduate School of Advanced Integration Science, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522, Japan
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16
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Fransson J, Kang MG, Yoon Y, Xiao S, Ochiai Y, Reno JL, Aoki N, Bird JP. Tuning the Fano resonance with an intruder continuum. Nano Lett 2014; 14:788-793. [PMID: 24460187 DOI: 10.1021/nl404133d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Through a combination of experiment and theory we establish the possibility of achieving strong tuning of Fano resonances (FRs), by allowing their usual two-path geometry to interfere with an additional, "intruder", continuum. As the coupling strength to this intruder is varied, we predict strong modulations of the resonance line shape that, in principle at least, may exceed the amplitude of the original FR itself. For a proof-of-concept demonstration of this phenomenon, we construct a nanoscale interferometer from nonlocally coupled quantum point contacts and utilize the unique features of their density of states to realize the intruder. External control of the intruder coupling is enabled by means of an applied magnetic field, in the presence of which we demonstrate the predicted distortions of the FR. This general scheme for resonant control should be broadly applicable to a variety of wave-based systems, opening up the possibility of new applications in areas such as chemical and biological sensing and secure communications.
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Affiliation(s)
- J Fransson
- Department of Physics and Astronomy, Uppsala University , Box 534, SE-751 21, Uppsala, Sweden
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17
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Lee J, Han JE, Xiao S, Song J, Reno JL, Bird JP. Formation of a protected sub-band for conduction in quantum point contacts under extreme biasing. Nat Nanotechnol 2014; 9:101-105. [PMID: 24441984 DOI: 10.1038/nnano.2013.297] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/26/2013] [Accepted: 12/05/2013] [Indexed: 06/03/2023]
Abstract
Managing energy dissipation is critical to the scaling of current microelectronics and to the development of novel devices that use quantum coherence to achieve enhanced functionality. To this end, strategies are needed to tailor the electron-phonon interaction, which is the dominant mechanism for cooling non-equilibrium ('hot') carriers. In experiments aimed at controlling the quantum state, this interaction causes decoherence that fundamentally disrupts device operation. Here, we show a contrasting behaviour, in which strong electron-phonon scattering can instead be used to generate a robust mode for electrical conduction in GaAs quantum point contacts, driven into extreme non-equilibrium by nanosecond voltage pulses. When the amplitude of these pulses is much larger than all other relevant energy scales, strong electron-phonon scattering induces an attraction between electrons in the quantum-point-contact channel, which leads to the spontaneous formation of a narrow current filament and to a renormalization of the electronic states responsible for transport. The lowest of these states coalesce to form a sub-band separated from all others by an energy gap larger than the source voltage. Evidence for this renormalization is provided by a suppression of heating-related signatures in the transient conductance, which becomes pinned near 2e(2)/h (e, electron charge; h, Planck constant) for a broad range of source and gate voltages. This collective non-equilibrium mode is observed over a wide range of temperature (4.2-300 K) and may provide an effective means to manage electron-phonon scattering in nanoscale devices.
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Affiliation(s)
- J Lee
- Department of Electrical Engineering, University at Buffalo, State University of New York, 230 Davis Hall, Buffalo, New York 14260-1900, USA
| | - J E Han
- Department of Physics, University at Buffalo, State University of New York, 239 Fronczak Hall, Buffalo, New York 14260-1500, USA
| | - S Xiao
- Department of Electrical Engineering, University at Buffalo, State University of New York, 230 Davis Hall, Buffalo, New York 14260-1900, USA
| | - J Song
- Department of Electrical Engineering, University at Buffalo, State University of New York, 230 Davis Hall, Buffalo, New York 14260-1900, USA
| | - J L Reno
- CINT, Sandia National Laboratories, Department 1131, MS 1303, Albuquerque, New Mexico 87185, USA
| | - J P Bird
- Department of Electrical Engineering, University at Buffalo, State University of New York, 230 Davis Hall, Buffalo, New York 14260-1900, USA
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18
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Somphonsane R, Ramamoorthy H, Bohra G, He G, Ferry DK, Ochiai Y, Aoki N, Bird JP. Fast energy relaxation of hot carriers near the Dirac point of graphene. Nano Lett 2013; 13:4305-4310. [PMID: 23965117 DOI: 10.1021/nl4020777] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
We investigate energy relaxation of hot carriers in monolayer and bilayer graphene devices, demonstrating that the relaxation rate increases significantly as the Dirac point is approached from either the conduction or valence band. This counterintuitive behavior appears consistent with ideas of charge puddling under disorder, suggesting that it becomes very difficult to excite carriers out of these localized regions. These results therefore demonstrate how the peculiar properties of graphene extend also to the behavior of its nonequilibrium carriers.
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Affiliation(s)
- R Somphonsane
- Department of Physics, University at Buffalo , Buffalo, New York 14260-1500, United States
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19
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Kim T, Chamberlin RV, Bird JP. Large magnetoresistance of nickel-silicide nanowires: non-equilibrium heating of magnetically-coupled dangling bonds. Nano Lett 2013; 13:1106-1110. [PMID: 23421719 DOI: 10.1021/nl3044585] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
We demonstrate large (>100%) time-dependent magnetoresistance in nickel-silicide nanowires and develop a thermodynamic model for this behavior. The model describes nonequilibrium heating of localized spins in an increasing magnetic field. We find a strong interaction between spins but no long-range magnetic order. The spins likely come from unpaired dangling bonds in the interfacial layers of the nanowires. The model indicates that although these bonds couple weakly to a thermal bath, they dominate the nanowire resistance.
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Affiliation(s)
- T Kim
- Department of Electrical Engineering, Arizona State University, Tempe, Arizona 85287-5706, United States
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20
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Lo ST, Wang YT, Bohra G, Comfort E, Lin TY, Kang MG, Strasser G, Bird JP, Huang CF, Lin LH, Chen JC, Liang CT. Insulator, semiclassical oscillations and quantum Hall liquids at low magnetic fields. J Phys Condens Matter 2012; 24:405601. [PMID: 22968955 DOI: 10.1088/0953-8984/24/40/405601] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Magneto-transport measurements are performed on two-dimensional GaAs electron systems to probe the quantum Hall (QH) effect at low magnetic fields. Oscillations following the Shubnikov-de Haas (SdH) formula are observed in the transition from the insulator to QH liquid when the observed almost temperature-independent Hall slope indicates insignificant interaction correction. Our study shows that the existence of SdH oscillations in such a transition can be understood based on the non-interacting model.
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Affiliation(s)
- Shun-Tsung Lo
- Graduate Institute of Applied Physics, National Taiwan University, Taipei 106, Taiwan
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21
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Brunner R, Ferry DK, Akis R, Meisels R, Kuchar F, Burke AM, Bird JP. Open quantum dots: II. Probing the classical to quantum transition. J Phys Condens Matter 2012; 24:343202. [PMID: 22871799 DOI: 10.1088/0953-8984/24/34/343202] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Open quantum dots provide a natural system in which to study both classical and quantum features of transport. From the classical point of view these dots possess a mixed phase space which yields families of closed, regular orbits as well as an expansive sea of chaos. An important question concerns the manner in which these classical states evolve into the set of quantum states that populate the dot in the quantum limit. In the reverse direction, the manner in which the quantum states evolve to the classical world is governed strongly by Zurek's decoherence theory. This was discussed from the quantum perspective in an earlier review (Ferry et al 2011 Semicond. Sci. Technol. 26 043001). Here, we discuss the nature of the various classical states, how they are formed, how they progress to the quantum world, and the signatures that they create in magnetotransport and general conductance studies of these dots.
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Affiliation(s)
- R Brunner
- Institut für Physik, Montanuniversitaet Leoben, A-8700 Leoben, Austria
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22
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Bird JP, Buchanan GM, Lees AC, Clay RP, Develey PF, Yépez I, Butchart SHM. Integrating spatially explicit habitat projections into extinction risk assessments: a reassessment of Amazonian avifauna incorporating projected deforestation. DIVERS DISTRIB 2011. [DOI: 10.1111/j.1472-4642.2011.00843.x] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
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23
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Hoffmann M, Hilton-Taylor C, Angulo A, Böhm M, Brooks TM, Butchart SHM, Carpenter KE, Chanson J, Collen B, Cox NA, Darwall WRT, Dulvy NK, Harrison LR, Katariya V, Pollock CM, Quader S, Richman NI, Rodrigues ASL, Tognelli MF, Vié JC, Aguiar JM, Allen DJ, Allen GR, Amori G, Ananjeva NB, Andreone F, Andrew P, Aquino Ortiz AL, Baillie JEM, Baldi R, Bell BD, Biju SD, Bird JP, Black-Decima P, Blanc JJ, Bolaños F, Bolivar-G W, Burfield IJ, Burton JA, Capper DR, Castro F, Catullo G, Cavanagh RD, Channing A, Chao NL, Chenery AM, Chiozza F, Clausnitzer V, Collar NJ, Collett LC, Collette BB, Cortez Fernandez CF, Craig MT, Crosby MJ, Cumberlidge N, Cuttelod A, Derocher AE, Diesmos AC, Donaldson JS, Duckworth JW, Dutson G, Dutta SK, Emslie RH, Farjon A, Fowler S, Freyhof J, Garshelis DL, Gerlach J, Gower DJ, Grant TD, Hammerson GA, Harris RB, Heaney LR, Hedges SB, Hero JM, Hughes B, Hussain SA, Icochea M J, Inger RF, Ishii N, Iskandar DT, Jenkins RKB, Kaneko Y, Kottelat M, Kovacs KM, Kuzmin SL, La Marca E, Lamoreux JF, Lau MWN, Lavilla EO, Leus K, Lewison RL, Lichtenstein G, Livingstone SR, Lukoschek V, Mallon DP, McGowan PJK, McIvor A, Moehlman PD, Molur S, Muñoz Alonso A, Musick JA, Nowell K, Nussbaum RA, Olech W, Orlov NL, Papenfuss TJ, Parra-Olea G, Perrin WF, Polidoro BA, Pourkazemi M, Racey PA, Ragle JS, Ram M, Rathbun G, Reynolds RP, Rhodin AGJ, Richards SJ, Rodríguez LO, Ron SR, Rondinini C, Rylands AB, Sadovy de Mitcheson Y, Sanciangco JC, Sanders KL, Santos-Barrera G, Schipper J, Self-Sullivan C, Shi Y, Shoemaker A, Short FT, Sillero-Zubiri C, Silvano DL, Smith KG, Smith AT, Snoeks J, Stattersfield AJ, Symes AJ, Taber AB, Talukdar BK, Temple HJ, Timmins R, Tobias JA, Tsytsulina K, Tweddle D, Ubeda C, Valenti SV, van Dijk PP, Veiga LM, Veloso A, Wege DC, Wilkinson M, Williamson EA, Xie F, Young BE, Akçakaya HR, Bennun L, Blackburn TM, Boitani L, Dublin HT, da Fonseca GAB, Gascon C, Lacher TE, Mace GM, Mainka SA, McNeely JA, Mittermeier RA, Reid GM, Rodriguez JP, Rosenberg AA, Samways MJ, Smart J, Stein BA, Stuart SN. The impact of conservation on the status of the world's vertebrates. Science 2010; 330:1503-9. [PMID: 20978281 DOI: 10.1126/science.1194442] [Citation(s) in RCA: 662] [Impact Index Per Article: 47.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Using data for 25,780 species categorized on the International Union for Conservation of Nature Red List, we present an assessment of the status of the world's vertebrates. One-fifth of species are classified as Threatened, and we show that this figure is increasing: On average, 52 species of mammals, birds, and amphibians move one category closer to extinction each year. However, this overall pattern conceals the impact of conservation successes, and we show that the rate of deterioration would have been at least one-fifth again as much in the absence of these. Nonetheless, current conservation efforts remain insufficient to offset the main drivers of biodiversity loss in these groups: agricultural expansion, logging, overexploitation, and invasive alien species.
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Affiliation(s)
- Michael Hoffmann
- IUCN SSC Species Survival Commission, c/o United Nations Environment Programme World Conservation Monitoring Centre, 219 Huntingdon Road, Cambridge CB3 0DL, UK.
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Bell M, Sergeev A, Bird JP, Mitin V, Verevkin A. Crossover from Fermi liquid to multichannel Luttinger liquid in high-mobility quantum wires. Phys Rev Lett 2010; 104:046805. [PMID: 20366730 DOI: 10.1103/physrevlett.104.046805] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/06/2009] [Indexed: 05/29/2023]
Abstract
We investigate the electrical conductance of long, high-mobility quantum wires formed by the split-gate technique, which allows for adjustment of the wire width and the number of one-dimensional electron subbands, n. In wires with 3<or=n<or=8, a logarithmic temperature dependence of the conductance is observed for 1<T<10 K, which reaches as much as 30% of the Drude conductance. In even narrower wires, the logarithmic dependence changes to a power-law variation. Our observations are shown to be in good agreement with recent theoretical studies, which attribute the logarithmic term to interaction effects in a weakly disordered quasi-one-dimensional conductor. This interaction correction is associated with the emergence of a crossover from a quasi-one-dimensional weakly disordered Fermi liquid to a multichannel Luttinger liquid.
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Affiliation(s)
- M Bell
- Electrical Engineering Department, University at Buffalo, Buffalo, New York 14260, USA
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25
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Ujiie Y, Motooka S, Morimoto T, Aoki N, Ferry DK, Bird JP, Ochiai Y. Regular conductance fluctuations indicative of quasi-ballistic transport in bilayer graphene. J Phys Condens Matter 2009; 21:382202. [PMID: 21832362 DOI: 10.1088/0953-8984/21/38/382202] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Quasi-periodic conductance fluctuations are observed in the low-temperature magneto-conductance of a bilayer graphene sample. The quasi-periodic nature of the fluctuations is confirmed by their Fourier power spectrum, which consists of just a small number of dominant frequency components. From an experimental study of these features, which are highly reminiscent of those reported previously for ballistic semiconductor quantum dots, we suggest that they are associated with the formation of an open quantum dot in the submicron graphene sample.
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Affiliation(s)
- Y Ujiie
- Graduate School of Advanced Integration Science, Chiba University, 1-33, Yayoi-cho, Inage-ku, Chiba 263-8522, Japan
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26
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Kim T, Chamberlin RV, Bennett PA, Bird JP. Dynamical characteristics of the giant magneto-resistance of epitaxial silicide nanowires. Nanotechnology 2009; 20:135401. [PMID: 19420499 DOI: 10.1088/0957-4484/20/13/135401] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
We study the dynamical properties of a hugely hysteretic magneto-resistance in epitaxially formed silicide nanowires, and propose a model for this remarkable effect in which it is attributed to the collective interactions among interfacial spins associated with dangling bonds. According to our model, the dynamic character of this effect reflects a competitive tendency for the interfacial spins to align in different collective configurations (random, ordered, and multi-domain). Our work thus provides a dramatic demonstration of how the collective interactions among interfacial spins can modify the properties of nonmagnetic nanostructures.
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Affiliation(s)
- T Kim
- Department of Electrical Engineering, Arizona State University, Tempe, AZ 85287-5706, USA
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27
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Yoon Y, Mourokh L, Morimoto T, Aoki N, Ochiai Y, Reno JL, Bird JP. Probing the microscopic structure of bound states in quantum point contacts. Phys Rev Lett 2007; 99:136805. [PMID: 17930622 DOI: 10.1103/physrevlett.99.136805] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/21/2007] [Indexed: 05/25/2023]
Abstract
Using an approach that allows us to probe the electronic structure of strongly pinched-off quantum point contacts (QPCs), we provide evidence for the formation of self-consistently realized bound states (BSs) in these structures. Our approach exploits the resonant interaction between closely coupled QPCs, and demonstrates that the BSs may give rise to a robust confinement of single spins, which show clear Zeeman splitting in a magnetic field.
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Affiliation(s)
- Y Yoon
- Department of Electrical Engineering, University at Buffalo, the State University of New York, Buffalo, New York 14260-1920, USA
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28
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Brunner R, Meisels R, Kuchar F, Akis R, Ferry DK, Bird JP. Draining of the sea of chaos: role of resonant transmission and reflection in an array of billiards. Phys Rev Lett 2007; 98:204101. [PMID: 17677700 DOI: 10.1103/physrevlett.98.204101] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/15/2006] [Indexed: 05/16/2023]
Abstract
We investigate the dynamics of a system of coupled electron billiards by using a magnetic field to dramatically modify the underlying mixed phase space. At specific values of the magnetic field the sea of chaos is drained. At these fields there exist reflected or transmitted orbits associated with maxima and minima in the experimentally observed magnetoresistance. These effects are studied by comparing the classical and quantum-mechanical phase-space dynamics leading to a basic understanding of the role of chaos in the transport in an array of billiards.
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Affiliation(s)
- R Brunner
- Institute of Physics, University of Leoben, A-8700 Leoben, Austria
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29
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Morimoto T, Henmi M, Naito R, Tsubaki K, Aoki N, Bird JP, Ochiai Y. Resonantly enhanced nonlinear conductance in long quantum point contacts near pinch-off. Phys Rev Lett 2006; 97:096801. [PMID: 17026388 DOI: 10.1103/physrevlett.97.096801] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/17/2005] [Indexed: 05/12/2023]
Abstract
We report on a remarkable resonance in the differential conductance of long quantum point contacts (QPCs) that is observed as a precursor to regular quantized transport. This effect is increasingly pronounced in longer QPCs, in which the differential conductance may resonantly exceed 2e2/h. From a study of the experimental characteristics of this feature, we suggest that it may be associated with the formation of a well-resolved energy gap that opens dynamically as a result of enhanced many-body interactions in long QPCs.
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Affiliation(s)
- T Morimoto
- Graduate School of Science and Technology, Chiba University, Inage-ku, Chiba 263-8522, Japan
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30
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Ferry DK, Akis R, Bird JP. Einselection in action: decoherence and pointer states in open quantum dots. Phys Rev Lett 2004; 93:026803. [PMID: 15323938 DOI: 10.1103/physrevlett.93.026803] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/05/2004] [Indexed: 05/24/2023]
Abstract
Recent work on the role of decoherence has suggested that the decay of quantum effects is governed by a discrete set of pointer states, which affect the quantum to classical correspondence. We show that the conductance oscillations exhibited by open quantum dots are governed by a discrete set of stable quantum states which have the properties of the pointer states, and which are closely related to trapped classical orbits in the open dot.
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Affiliation(s)
- D K Ferry
- Department of Electrical Engineering, Center for Solid State Electronics Research, Arizona State University, Tempe, Arizona 85287-5706, USA
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Puller VI, Mourokh LG, Shailos A, Bird JP. Detection of local-moment formation using the resonant interaction between coupled quantum wires. Phys Rev Lett 2004; 92:096802. [PMID: 15089499 DOI: 10.1103/physrevlett.92.096802] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/24/2003] [Indexed: 05/24/2023]
Abstract
We study the influence of many-body interactions on the transport characteristics of a pair of quantum wires that are coupled to each other by means of a quantum dot. Under conditions where a local magnetic moment is formed in one of the wires, tunnel coupling to the other gives rise to an associated peak in its density of states, which can be detected directly in a conductance measurement. Our theory is therefore able to account for the key observations in the recent study of T. Morimoto et al. [Appl. Phys. Lett., ()]], and demonstrates that coupled quantum wires may be used as a system for the detection of local magnetic-moment formation.
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Affiliation(s)
- V I Puller
- Department of Physics and Engineering Physics, Stevens Institute of Technology, Hoboken, New Jersey 07030, USA
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Ramamoorthy A, Akis R, Bird JP, Maemoto T, Ferry DK, Inoue M. Signatures of dynamical tunneling in semiclassical quantum dots. ACTA ACUST UNITED AC 2003; 68:026221. [PMID: 14525098 DOI: 10.1103/physreve.68.026221] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2003] [Indexed: 11/07/2022]
Abstract
We study transport in large, and strongly open, quantum dots, which might typically be viewed as lying well within the semiclassical regime. The low-temperature magnetoresistance of these structures exhibits regular fluctuations, with just a small number of dominant frequency components, indicative of the presence of dynamical tunneling into regular orbits. Support for these ideas is provided by the results of numerical simulations, which reveal wave function scarring by classically inaccessible orbits, which is found to persist even in the presence of a moderately disordered dot potential. Our results suggest that dynamical tunneling may play a more generic role in transport through mesoscopic structures than has thus far been appreciated.
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Affiliation(s)
- A Ramamoorthy
- Nanostructures Research Group, Department of Electrical Engineering, Arizona State University, Tempe, Arizona 85287-5706, USA
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Micolich AP, Taylor RP, Davies AG, Bird JP, Newbury R, Fromhold TM, Ehlert A, Linke H, Macks LD, Tribe WR, Linfield EH, Ritchie DA, Cooper J, Aoyagi Y, Wilkinson PB. Evolution of fractal patterns during a classical-quantum transition. Phys Rev Lett 2001; 87:036802. [PMID: 11461579 DOI: 10.1103/physrevlett.87.036802] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/14/2000] [Indexed: 05/23/2023]
Abstract
We investigate how fractals evolve into nonfractal behavior as the generation process is gradually suppressed. Fractals observed in the conductance of semiconductor billiards are of particular interest because the generation process is semiclassical and can be suppressed by transitions towards either fully classical or fully quantum-mechanical conduction. Investigating a range of billiards, we identify a "universal" behavior in the changeover from fractal to nonfractal conductance, which is described by a smooth evolution rather than deterioration in the fractal scaling properties.
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Affiliation(s)
- A P Micolich
- Materials Science Institute, Physics Department, University of Oregon, Eugene, Oregon 97403-1274, USA
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Akis R, Ferry DK, Bird JP. Magnetotransport fluctuations in regular semiconductor ballistic quantum dots. Phys Rev B Condens Matter 1996; 54:17705-17715. [PMID: 9985899 DOI: 10.1103/physrevb.54.17705] [Citation(s) in RCA: 49] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Stopa M, Bird JP, Ishibashi K, Aoyagi Y, Sugano T. Giant backscattering magnetoresistance resonance and quantum dot electronic structure. Phys Rev Lett 1996; 76:2145-2148. [PMID: 10060617 DOI: 10.1103/physrevlett.76.2145] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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Bird JP, Ishibashi K, Aoyagi Y, Sugano T. Precise period doubling of the Aharonov-Bohm effect in a quantum dot at high magnetic fields. Phys Rev B Condens Matter 1996; 53:3642-3645. [PMID: 9983911 DOI: 10.1103/physrevb.53.3642] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Bird JP, Olatona DM, Newbury R, Taylor RP, Ishibashi K, Stopa M, Aoyagi Y, Sugano T, Ochiai Y. Lead-induced transition to chaos in ballistic mesoscopic billiards. Phys Rev B Condens Matter 1995; 52:14336-14339. [PMID: 9980753 DOI: 10.1103/physrevb.52.r14336] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Bird JP, Ishibashi K, Ferry DK, Ochiai Y, Aoyagi Y, Sugano T. Spectral characteristics of conductance fluctuations in ballistic quantum dots: The influence of finite magnetic field and temperature. Phys Rev B Condens Matter 1995; 52:8295-8304. [PMID: 9979830 DOI: 10.1103/physrevb.52.8295] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Bird JP, Ishibashi K, Ochiai Y, Lakrimi M, Grassie AD, Hutchings KM, Aoyagi Y, Sugano T. Breakdown of correlated diffusion in quasiballistic quantum wires at high magnetic fields. Phys Rev B Condens Matter 1995; 52:1793-1799. [PMID: 9981246 DOI: 10.1103/physrevb.52.1793] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Bird JP, Ishibashi K, Ferry DK, Ochiai Y, Aoyagi Y, Sugano T. Phase breaking in ballistic quantum dots: Transition from two- to zero-dimensional behavior. Phys Rev B Condens Matter 1995; 51:18037-18040. [PMID: 9978850 DOI: 10.1103/physrevb.51.18037] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Bird JP, Ishibashi K, Aoyagi Y, Sugano T, Ochiai Y. Spectral characteristics of conductance fluctuations in ballistic quantum dots. Phys Rev B Condens Matter 1994; 50:18678-18681. [PMID: 9976313 DOI: 10.1103/physrevb.50.18678] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Bird JP, Ishibashi K, Stopa M, Aoyagi Y, Sugano T. Coulomb blockade of the Aharonov-Bohm effect in GaAs/AlxGa1-xAs quantum dots. Phys Rev B Condens Matter 1994; 50:14983-14990. [PMID: 9975846 DOI: 10.1103/physrevb.50.14983] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Bird JP, Ishibashi K, Stopa M, Taylor RP, Aoyagi Y, Sugano T. Magneto-Coulomb oscillations. Phys Rev B Condens Matter 1994; 49:11488-11491. [PMID: 10010012 DOI: 10.1103/physrevb.49.11488] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Onishi T, Kawabe M, Ishibashi K, Bird JP, Aoyagi Y, Sugano T, Ochiai Y. Scaling properties of universal conductance fluctuations in quasiballistic split-gate wires: Probing geometrical effects. Phys Rev B Condens Matter 1993; 48:12353-12356. [PMID: 10007600 DOI: 10.1103/physrevb.48.12353] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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