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Moon A, Li Y, McKeever C, Casas BW, Bravo M, Zheng W, Macy J, Petford-Long AK, McCandless GT, Chan JY, Phatak C, Santos EJG, Balicas L. Writing and Detecting Topological Charges in Exfoliated Fe 5-xGeTe 2. ACS Nano 2024; 18:4216-4228. [PMID: 38262067 DOI: 10.1021/acsnano.3c09234] [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] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/25/2024]
Abstract
Fe5-xGeTe2 is a promising two-dimensional (2D) van der Waals (vdW) magnet for practical applications, given its magnetic properties. These include Curie temperatures above room temperature, and topological spin textures─TST (both merons and skyrmions), responsible for a pronounced anomalous Hall effect (AHE) and its topological counterpart (THE), which can be harvested for spintronics. Here, we show that both the AHE and THE can be amplified considerably by just adjusting the thickness of exfoliated Fe5-xGeTe2, with THE becoming observable even in zero magnetic field due to a field-induced unbalance in topological charges. Using a complementary suite of techniques, including electronic transport, Lorentz transmission electron microscopy, and micromagnetic simulations, we reveal the emergence of substantial coercive fields upon exfoliation, which are absent in the bulk, implying thickness-dependent magnetic interactions that affect the TST. We detected a "magic" thickness t ≈ 30 nm where the formation of TST is maximized, inducing large magnitudes for the topological charge density (∼6.45 × 1020 cm-2), and the concomitant anomalous (ρxyA,max ≃22.6 μΩ cm) and topological (ρxyu,T 1≃5 μΩ cm) Hall resistivities at T ≈ 120 K. These values for ρxyA,max and ρxyu,T are higher than those found in magnetic topological insulators and, so far, the largest reported for 2D magnets. The hitherto unobserved THE under zero magnetic field could provide a platform for the writing and electrical detection of TST aiming at energy-efficient devices based on vdW ferromagnets.
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Affiliation(s)
- Alex Moon
- National High Magnetic Field Laboratory, 1800 E. Paul Dirac Dr., Tallahassee, Florida 32310, United States
- Department of Physics, Florida State University, 77 Chieftan Way, Tallahassee, Florida 32306, United States
| | - Yue Li
- Materials Science Division, Argonne National Laboratory, Lemont, Illinois 60439, United States
| | - Conor McKeever
- Institute for Condensed Matter and Complex Systems, School of Physics and Astronomy, The University of Edinburgh, Edinburgh EH9 3FD, U.K
| | - Brian W Casas
- National High Magnetic Field Laboratory, 1800 E. Paul Dirac Dr., Tallahassee, Florida 32310, United States
| | - Moises Bravo
- Department of Chemistry and Biochemistry, Baylor University, Waco, Texas 76798, United States
| | - Wenkai Zheng
- National High Magnetic Field Laboratory, 1800 E. Paul Dirac Dr., Tallahassee, Florida 32310, United States
- Department of Physics, Florida State University, 77 Chieftan Way, Tallahassee, Florida 32306, United States
| | - Juan Macy
- National High Magnetic Field Laboratory, 1800 E. Paul Dirac Dr., Tallahassee, Florida 32310, United States
- Department of Physics, Florida State University, 77 Chieftan Way, Tallahassee, Florida 32306, United States
| | - Amanda K Petford-Long
- Materials Science Division, Argonne National Laboratory, Lemont, Illinois 60439, United States
- Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208, United States
| | - Gregory T McCandless
- Department of Chemistry and Biochemistry, Baylor University, Waco, Texas 76798, United States
| | - Julia Y Chan
- Department of Chemistry and Biochemistry, Baylor University, Waco, Texas 76798, United States
| | - Charudatta Phatak
- Materials Science Division, Argonne National Laboratory, Lemont, Illinois 60439, United States
- Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208, United States
| | - Elton J G Santos
- Institute for Condensed Matter and Complex Systems, School of Physics and Astronomy, The University of Edinburgh, Edinburgh EH9 3FD, U.K
- Higgs Centre for Theoretical Physics, The University of Edinburgh, Edinburgh EH9 3FD, U.K
| | - Luis Balicas
- National High Magnetic Field Laboratory, 1800 E. Paul Dirac Dr., Tallahassee, Florida 32310, United States
- Department of Physics, Florida State University, 77 Chieftan Way, Tallahassee, Florida 32306, United States
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2
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Li Y, Oh T, Son J, Song J, Kim MK, Song D, Kim S, Chang SH, Kim C, Yang BJ, Noh TW. Correlated Magnetic Weyl Semimetal State in Strained Pr 2 Ir 2 O 7. Adv Mater 2021; 33:e2008528. [PMID: 33988861 DOI: 10.1002/adma.202008528] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/17/2020] [Revised: 03/17/2021] [Indexed: 06/12/2023]
Abstract
Correlated topological phases (CTPs) with interplay between topology and electronic correlations have attracted tremendous interest in condensed matter physics. Therein, correlated Weyl semimetals (WSMs) are rare in nature and, thus, have so far been less investigated experimentally. In particular, the experimental realization of the interacting WSM state with logarithmic Fermi velocity renormalization has not been achieved yet. Here, experimental evidence of a correlated magnetic WSM state with logarithmic renormalization in strained pyrochlore iridate Pr2 Ir2 O7 (PIO) which is a paramagnetic Luttinger semimetal in bulk, is reported. Benefitting from epitaxial strain, "bulk-absent" all-in-all-out antiferromagnetic ordering can be stabilized in PIO film, which breaks time-reversal symmetry and leads to a magnetic WSM state. With further analysis of the experimental data and renormalization group calculations, an interacting Weyl liquid state with logarithmically renormalized Fermi velocity, similar to that in graphene, is found, dressed by long-range Coulomb interactions. This work highlights the interplay of strain, magnetism, and topology with electronic correlations, and paves the way for strain-engineering of CTPs in pyrochlore iridates.
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Affiliation(s)
- Yangyang Li
- Center for Correlated Electron Systems, Institute for Basic Science (IBS), Seoul, 08826, Republic of Korea
- Department of Physics and Astronomy, Seoul National University, Seoul, 08826, Republic of Korea
| | - Taekoo Oh
- Center for Correlated Electron Systems, Institute for Basic Science (IBS), Seoul, 08826, Republic of Korea
- Department of Physics and Astronomy, Seoul National University, Seoul, 08826, Republic of Korea
- Center for Theoretical Physics (CTP), Seoul National University, Seoul, 08826, Republic of Korea
| | - Jaeseok Son
- Center for Correlated Electron Systems, Institute for Basic Science (IBS), Seoul, 08826, Republic of Korea
- Department of Physics and Astronomy, Seoul National University, Seoul, 08826, Republic of Korea
| | - Jeongkeun Song
- Center for Correlated Electron Systems, Institute for Basic Science (IBS), Seoul, 08826, Republic of Korea
- Department of Physics and Astronomy, Seoul National University, Seoul, 08826, Republic of Korea
| | - Mi Kyung Kim
- Center for Correlated Electron Systems, Institute for Basic Science (IBS), Seoul, 08826, Republic of Korea
- Department of Physics and Astronomy, Seoul National University, Seoul, 08826, Republic of Korea
| | - Dongjun Song
- Center for Correlated Electron Systems, Institute for Basic Science (IBS), Seoul, 08826, Republic of Korea
- Department of Physics and Astronomy, Seoul National University, Seoul, 08826, Republic of Korea
| | - Sukhyun Kim
- Center for Correlated Electron Systems, Institute for Basic Science (IBS), Seoul, 08826, Republic of Korea
- Department of Physics and Astronomy, Seoul National University, Seoul, 08826, Republic of Korea
| | - Seo Hyoung Chang
- Department of Physics, Chung-Ang University, Seoul, 156-756, Republic of Korea
| | - Changyoung Kim
- Center for Correlated Electron Systems, Institute for Basic Science (IBS), Seoul, 08826, Republic of Korea
- Department of Physics and Astronomy, Seoul National University, Seoul, 08826, Republic of Korea
| | - Bohm-Jung Yang
- Center for Correlated Electron Systems, Institute for Basic Science (IBS), Seoul, 08826, Republic of Korea
- Department of Physics and Astronomy, Seoul National University, Seoul, 08826, Republic of Korea
- Center for Theoretical Physics (CTP), Seoul National University, Seoul, 08826, Republic of Korea
| | - Tae Won Noh
- Center for Correlated Electron Systems, Institute for Basic Science (IBS), Seoul, 08826, Republic of Korea
- Department of Physics and Astronomy, Seoul National University, Seoul, 08826, Republic of Korea
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3
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Chen T, Tomita T, Minami S, Fu M, Koretsune T, Kitatani M, Muhammad I, Nishio-Hamane D, Ishii R, Ishii F, Arita R, Nakatsuji S. Anomalous transport due to Weyl fermions in the chiral antiferromagnets Mn 3X, X = Sn, Ge. Nat Commun 2021; 12:572. [PMID: 33495448 PMCID: PMC7835387 DOI: 10.1038/s41467-020-20838-1] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2019] [Accepted: 11/22/2020] [Indexed: 11/28/2022] Open
Abstract
The recent discoveries of strikingly large zero-field Hall and Nernst effects in antiferromagnets Mn3X (X = Sn, Ge) have brought the study of magnetic topological states to the forefront of condensed matter research and technological innovation. These effects are considered fingerprints of Weyl nodes residing near the Fermi energy, promoting Mn3X (X = Sn, Ge) as a fascinating platform to explore the elusive magnetic Weyl fermions. In this review, we provide recent updates on the insights drawn from experimental and theoretical studies of Mn3X (X = Sn, Ge) by combining previous reports with our new, comprehensive set of transport measurements of high-quality Mn3Sn and Mn3Ge single crystals. In particular, we report magnetotransport signatures specific to chiral anomalies in Mn3Ge and planar Hall effect in Mn3Sn, which have not yet been found in earlier studies. The results summarized here indicate the essential role of magnetic Weyl fermions in producing the large transverse responses in the absence of magnetization. The large anomalous Hall (AHE) and anomalous Nernst effects (ANE) in antiferromagnets Mn3Sn/Mn3Ge are considered fingerprints of Weyl nodes residing near the Fermi energy. Here, the authors review the results from previous studies combining with new transport measurements on Mn3Sn/Mn3Ge single crystals, suggesting the essential role of magnetic Weyl fermions in explaining the AHE and ANE.
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Affiliation(s)
- Taishi Chen
- Department of Physics, University of Tokyo, Tokyo, Japan.,Institute for Solid State Physics, University of Tokyo, Kashiwa, Chiba, Japan
| | - Takahiro Tomita
- Institute for Solid State Physics, University of Tokyo, Kashiwa, Chiba, Japan.,CREST, Japan Science and Technology Agency (JST), Honcho Kawaguchi, Japan
| | - Susumu Minami
- Department of Physics, University of Tokyo, Tokyo, Japan.,RIKEN Center for Emergent Matter Science (CEMS), Wako, Saitama, Japan.,Nanomaterials Research Institute, Kanazawa University, Kanazawa, Japan
| | - Mingxuan Fu
- Department of Physics, University of Tokyo, Tokyo, Japan.,Institute for Solid State Physics, University of Tokyo, Kashiwa, Chiba, Japan
| | | | - Motoharu Kitatani
- RIKEN Center for Emergent Matter Science (CEMS), Wako, Saitama, Japan
| | - Ikhlas Muhammad
- Institute for Solid State Physics, University of Tokyo, Kashiwa, Chiba, Japan
| | | | - Rieko Ishii
- Institute for Solid State Physics, University of Tokyo, Kashiwa, Chiba, Japan
| | - Fumiyuki Ishii
- RIKEN Center for Emergent Matter Science (CEMS), Wako, Saitama, Japan.,Nanomaterials Research Institute, Kanazawa University, Kanazawa, Japan
| | - Ryotaro Arita
- CREST, Japan Science and Technology Agency (JST), Honcho Kawaguchi, Japan.,RIKEN Center for Emergent Matter Science (CEMS), Wako, Saitama, Japan.,Department of Applied Physics, University of Tokyo, Tokyo, Japan
| | - Satoru Nakatsuji
- Department of Physics, University of Tokyo, Tokyo, Japan. .,Institute for Solid State Physics, University of Tokyo, Kashiwa, Chiba, Japan. .,CREST, Japan Science and Technology Agency (JST), Honcho Kawaguchi, Japan. .,Institute for Quantum Matter and Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD, USA. .,Trans-scale Quantum Science Institute, University of Tokyo, Tokyo, Japan.
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4
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Ni JM, Huang YY, Cheng EJ, Yu YJ, Pan BL, Li Q, Xu LM, Tian ZM, Li SY. Giant isotropic magneto-thermal conductivity of metallic spin liquid candidate Pr 2Ir 2O 7 with quantum criticality. Nat Commun 2021; 12:307. [PMID: 33436565 PMCID: PMC7804409 DOI: 10.1038/s41467-020-20562-w] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [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: 12/16/2019] [Accepted: 12/09/2020] [Indexed: 12/05/2022] Open
Abstract
Spin liquids are exotic states with no spontaneous symmetry breaking down to zero-temperature because of the highly entangled and fluctuating spins in frustrated systems. Exotic excitations like magnetic monopoles, visons, and photons may emerge from quantum spin ice states, a special kind of spin liquids in pyrochlore lattices. These materials usually are insulators, with an exception of the pyrochlore iridate Pr2Ir2O7, which was proposed as a metallic spin liquid located at a zero-field quantum critical point. Here we report the ultralow-temperature thermal conductivity measurements on Pr2Ir2O7. The Wiedemann-Franz law is verified at high fields and inferred at zero field, suggesting no breakdown of Landau quasiparticles at the quantum critical point, and the absence of mobile fermionic excitations. This result puts strong constraints on the description of the quantum criticality in Pr2Ir2O7. Unexpectedly, although the specific heats are anisotropic with respect to magnetic field directions, the thermal conductivities display the giant but isotropic response. This indicates that quadrupolar interactions and quantum fluctuations are important, which will help determine the true ground state of this material.
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Affiliation(s)
- J M Ni
- State Key Laboratory of Surface Physics, Department of Physics, and Laboratory of Advanced Materials, Fudan University, Shanghai, 200438, China
| | - Y Y Huang
- State Key Laboratory of Surface Physics, Department of Physics, and Laboratory of Advanced Materials, Fudan University, Shanghai, 200438, China
| | - E J Cheng
- State Key Laboratory of Surface Physics, Department of Physics, and Laboratory of Advanced Materials, Fudan University, Shanghai, 200438, China
| | - Y J Yu
- State Key Laboratory of Surface Physics, Department of Physics, and Laboratory of Advanced Materials, Fudan University, Shanghai, 200438, China
| | - B L Pan
- State Key Laboratory of Surface Physics, Department of Physics, and Laboratory of Advanced Materials, Fudan University, Shanghai, 200438, China
| | - Q Li
- State Key Laboratory of Surface Physics, Department of Physics, and Laboratory of Advanced Materials, Fudan University, Shanghai, 200438, China
| | - L M Xu
- School of Physics, and Wuhan National High Magnetic Field Center, Huazhong University of Science and Technology, Wuhan, 430074, China
| | - Z M Tian
- School of Physics, and Wuhan National High Magnetic Field Center, Huazhong University of Science and Technology, Wuhan, 430074, China.
| | - S Y Li
- State Key Laboratory of Surface Physics, Department of Physics, and Laboratory of Advanced Materials, Fudan University, Shanghai, 200438, China.
- Collaborative Innovation Center of Advanced Microstructures, Nanjing, 210093, China.
- Shanghai Research Center for Quantum Sciences, Shanghai, 201315, China.
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5
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Ohtsuki T, Tian Z, Endo A, Halim M, Katsumoto S, Kohama Y, Kindo K, Lippmaa M, Nakatsuji S. Strain-induced spontaneous Hall effect in an epitaxial thin film of a Luttinger semimetal. Proc Natl Acad Sci U S A 2019; 116:8803-8808. [PMID: 30988202 PMCID: PMC6500155 DOI: 10.1073/pnas.1819489116] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Pyrochlore iridates have provided a plethora of novel phenomena owing to the combination of topology and correlation. Among them, much attention has been paid to [Formula: see text], as it is known as a Luttinger semimetal characterized by quadratic band touching at the Brillouin zone center, suggesting that the topology of its electronic states can be tuned by a moderate lattice strain and external magnetic field. Here, we report that our epitaxial [Formula: see text] thin films grown by solid-state epitaxy exhibit a spontaneous Hall effect that persists up to 50 K without having spontaneous magnetization within our experimental accuracy. This indicates that the system breaks the time reversal symmetry at a temperature scale that is too high for the magnetism to be due to Pr 4f moments and must be related to magnetic order of the iridium 5d electrons. Moreover, our analysis finds that the chiral anomaly induces the negative contribution to the magnetoresistance only when a magnetic field and the electric current are parallel to each other. Our results indicate that the strained part of the thin film forms a magnetic Weyl semimetal state.
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Affiliation(s)
- Takumi Ohtsuki
- Institute for Solid State Physics, The University of Tokyo, Kashiwa, Chiba 277-8581, Japan;
| | - Zhaoming Tian
- Institute for Solid State Physics, The University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - Akira Endo
- Institute for Solid State Physics, The University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - Mario Halim
- Institute for Solid State Physics, The University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - Shingo Katsumoto
- Institute for Solid State Physics, The University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - Yoshimitsu Kohama
- Institute for Solid State Physics, The University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - Koichi Kindo
- Institute for Solid State Physics, The University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - Mikk Lippmaa
- Institute for Solid State Physics, The University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - Satoru Nakatsuji
- Institute for Solid State Physics, The University of Tokyo, Kashiwa, Chiba 277-8581, Japan;
- Core Research for Evolutionary Science and Technology, Japan Science and Technology Agency, 4-1-8 Honcho Kawaguchi, Saitama 332-0012, Japan
- Institute for Quantum Matter and Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218
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6
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Boettcher I, Herbut IF. Unconventional Superconductivity in Luttinger Semimetals: Theory of Complex Tensor Order and the Emergence of the Uniaxial Nematic State. Phys Rev Lett 2018; 120:057002. [PMID: 29481208 DOI: 10.1103/physrevlett.120.057002] [Citation(s) in RCA: 1] [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: 07/11/2017] [Indexed: 06/08/2023]
Abstract
We investigate unconventional superconductivity in three-dimensional electronic systems with the chemical potential close to a quadratic band touching point in the band dispersion. Short-range interactions can lead to d-wave superconductivity, described by a complex tensor order parameter. We elucidate the general structure of the corresponding Ginzburg-Landau free energy and apply these concepts to the case of an isotropic band touching point. For a vanishing chemical potential, the ground state of the system is given by the superconductor analogue of the uniaxial nematic state, which features line nodes in the excitation spectrum of quasiparticles. In contrast to the theory of real tensor order in liquid crystals, however, the ground state is selected here by the sextic terms in the free energy. At a finite chemical potential, the nematic state has an additional instability at weak coupling and low temperatures. In particular, the one-loop coefficients in the free energy indicate that at weak coupling genuinely complex orders, which break time-reversal symmetry, are energetically favored. We relate our analysis to recent measurements in the half-Heusler compound YPtBi and discuss the role of cubic crystal symmetry.
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Affiliation(s)
- Igor Boettcher
- Department of Physics, Simon Fraser University, Burnaby, British Columbia, Canada, V5A 1S6
| | - Igor F Herbut
- Department of Physics, Simon Fraser University, Burnaby, British Columbia, Canada, V5A 1S6
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7
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Ueda K, Oh T, Yang BJ, Kaneko R, Fujioka J, Nagaosa N, Tokura Y. Magnetic-field induced multiple topological phases in pyrochlore iridates with Mott criticality. Nat Commun 2017; 8:15515. [PMID: 28537276 DOI: 10.1038/ncomms15515] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2017] [Accepted: 04/03/2017] [Indexed: 11/13/2022] Open
Abstract
The interplay between electron correlation and spin–orbit coupling in solids has been proven to be an abundant gold mine for emergent topological phases. Here we report the results of systematic magnetotransport study on bandwidth-controlled pyrochlore iridates R2Ir2O7 near quantum metal-insulator transition (MIT). The application of a magnetic field along [001] crystallographic direction (H//[001]) significantly decreases resistivity while producing a unique Hall response, which indicates the emergence of the novel semi-metallic state in the course of the magnetic transformation from all-in all-out (AIAO, 4/0) to 2-in 2-out (2/2) spin configuration. For H//[111] that favours 3-in 1-out (3/1) configuration, by contrast, the resistivity exhibits saturation at a relatively high value typical of a semimetal. The observed properties can be identified to reflect the emergence of multiple Weyl semimetal states with varying numbers of Weyl points and line nodes in respective spin configurations. With tuning effective bandwidth, all these states appear to concentrate around the quantum MIT region, which may open a promising venue for topological phenomena and functions. The interplay between multiple electronic interactions in solid promotes the emergence of exotic phases. Here, Ueda et al. report magnetotransport study on pyrochlore iridates R2Ir2O7 near quantum metal-insulator transition reflecting the emergence of multiple Weyl semimetal states.
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8
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Abstract
The emergence of novel quantum ground states in correlated electron systems with strong spin-orbit coupling has been a recent subject of intensive studies. While it has been realized that spin-orbit coupling can provide non-trivial band topology in weakly interacting electron systems, as in topological insulators and semi-metals, the role of electron-electron interaction in strongly spin-orbit coupled systems has not been fully understood. The availability of new materials with significant electron correlation and strong spin-orbit coupling now makes such investigations possible. Many of these materials contain 5d or 4d transition metal elements; the prominent examples are iridium oxides or iridates. In this review, we succinctly discuss recent theoretical and experimental progress on this subject. After providing a brief overview, we focus on pyrochlore iridates and three-dimensional honeycomb iridates. In pyrochlore iridates, we discuss the quantum criticality of the bulk and surface states, and the relevance of the surface/boundary states in a number of topological and magnetic ground states, both in the bulk and thin film configurations. Experimental signatures of these boundary and bulk states are discussed. Domain wall formation and strongly-direction-dependent magneto-transport are also discussed. In regard to the three-dimensional honeycomb iridates, we consider possible quantum spin liquid phases and unusual magnetic orders in theoretical models with strongly bond-dependent interactions. These theoretical ideas and results are discussed in light of recent resonant x-ray scattering experiments on three-dimensional honeycomb iridates. We also contrast these results with the situation in two-dimensional honeycomb iridates. We conclude with the outlook on other related systems.
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Affiliation(s)
- Robert Schaffer
- Department of Physics and Center for Quantum Materials, University of Toronto, Toronto, Ontario M5S 1A7, Canada
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9
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Nakayama M, Kondo T, Tian Z, Ishikawa JJ, Halim M, Bareille C, Malaeb W, Kuroda K, Tomita T, Ideta S, Tanaka K, Matsunami M, Kimura S, Inami N, Ono K, Kumigashira H, Balents L, Nakatsuji S, Shin S. Slater to Mott Crossover in the Metal to Insulator Transition of Nd_{2}Ir_{2}O_{7}. Phys Rev Lett 2016; 117:056403. [PMID: 27517783 DOI: 10.1103/physrevlett.117.056403] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/18/2016] [Indexed: 06/06/2023]
Abstract
We present an angle-resolved photoemission study of the electronic structure of the three-dimensional pyrochlore iridate Nd_{2}Ir_{2}O_{7} through its magnetic metal-insulator transition. Our data reveal that metallic Nd_{2}Ir_{2}O_{7} has a quadratic band, touching the Fermi level at the Γ point, similar to that of Pr_{2}Ir_{2}O_{7}. The Fermi node state is, therefore, a common feature of the metallic phase of the pyrochlore iridates. Upon cooling below the transition temperature, this compound exhibits a gap opening with an energy shift of quasiparticle peaks like a band gap insulator. The quasiparticle peaks are strongly suppressed, however, with further decrease of temperature, and eventually vanish at the lowest temperature, leaving a nondispersive flat band lacking long-lived electrons. We thereby identify a remarkable crossover from Slater to Mott insulators with decreasing temperature. These observations explain the puzzling absence of Weyl points in this material, despite its proximity to the zero temperature metal-insulator transition.
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Affiliation(s)
- M Nakayama
- ISSP, University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - Takeshi Kondo
- ISSP, University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - Z Tian
- ISSP, University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - J J Ishikawa
- ISSP, University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - M Halim
- ISSP, University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - C Bareille
- ISSP, University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - W Malaeb
- ISSP, University of Tokyo, Kashiwa, Chiba 277-8581, Japan
- Physics Department, Faculty of Science, Beirut Arab University, Beirut 11-5020, Lebanon
| | - K Kuroda
- ISSP, University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - T Tomita
- ISSP, University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - S Ideta
- UVSOR Facility, Institute for Molecular Science, Okazaki 444-8585, Japan
| | - K Tanaka
- UVSOR Facility, Institute for Molecular Science, Okazaki 444-8585, Japan
| | - M Matsunami
- Toyota Technological Institute, Nagoya 468-8511, Japan
| | - S Kimura
- Graduate School of Frontier Biosciences, Osaka University, Suita, Osaka 565-0871, Japan
| | - N Inami
- Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki 305-0801, Japan
| | - K Ono
- Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki 305-0801, Japan
| | - H Kumigashira
- Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki 305-0801, Japan
| | - L Balents
- Kavli Institute for Theoretical Physics, Santa Barbara, California 93106, USA
| | - S Nakatsuji
- ISSP, University of Tokyo, Kashiwa, Chiba 277-8581, Japan
- CREST, Japan Science and Technology Agency (JST), 4-1-8 Honcho Kawaguchi, Saitama 332-0012, Japan
| | - S Shin
- ISSP, University of Tokyo, Kashiwa, Chiba 277-8581, Japan
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10
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Kondo T, Nakayama M, Chen R, Ishikawa JJ, Moon EG, Yamamoto T, Ota Y, Malaeb W, Kanai H, Nakashima Y, Ishida Y, Yoshida R, Yamamoto H, Matsunami M, Kimura S, Inami N, Ono K, Kumigashira H, Nakatsuji S, Balents L, Shin S. Quadratic Fermi node in a 3D strongly correlated semimetal. Nat Commun 2015; 6:10042. [PMID: 26640114 PMCID: PMC4686656 DOI: 10.1038/ncomms10042] [Citation(s) in RCA: 126] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2015] [Accepted: 10/29/2015] [Indexed: 11/25/2022] Open
Abstract
Strong spin–orbit coupling fosters exotic electronic states such as topological insulators and superconductors, but the combination of strong spin–orbit and strong electron–electron interactions is just beginning to be understood. Central to this emerging area are the 5d transition metal iridium oxides. Here, in the pyrochlore iridate Pr2Ir2O7, we identify a non-trivial state with a single-point Fermi node protected by cubic and time-reversal symmetries, using a combination of angle-resolved photoemission spectroscopy and first-principles calculations. Owing to its quadratic dispersion, the unique coincidence of four degenerate states at the Fermi energy, and strong Coulomb interactions, non-Fermi liquid behaviour is predicted, for which we observe some evidence. Our discovery implies that Pr2Ir2O7 is a parent state that can be manipulated to produce other strongly correlated topological phases, such as topological Mott insulator, Weyl semimetal, and quantum spin and anomalous Hall states. 5d transition metal iridates provide a platform to study the combined effects of strong spin orbit coupling and strong electronic correlations. Here, the authors find a quadratic band touching in the band structure of Pr2Ir2O7, suggesting it may be tuned to form various strongly correlated topological phases.
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Affiliation(s)
- Takeshi Kondo
- ISSP, University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - M Nakayama
- ISSP, University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - R Chen
- Physics Department, University of California, Santa Barbara, California 93106, USA.,Physics Department, University of California, Berkeley, California 94720, USA.,Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - J J Ishikawa
- ISSP, University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - E-G Moon
- Physics Department, University of California, Santa Barbara, California 93106, USA.,Department of Physics, Korea Advanced Institute of Science and Technology, Daejeon 305-701, Korea
| | - T Yamamoto
- ISSP, University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - Y Ota
- ISSP, University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - W Malaeb
- ISSP, University of Tokyo, Kashiwa, Chiba 277-8581, Japan.,Physics Department, Faculty of Science, Beirut Arab University, P. O. Box 11-5020 Beirut, Lebanon
| | - H Kanai
- ISSP, University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - Y Nakashima
- ISSP, University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - Y Ishida
- ISSP, University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - R Yoshida
- ISSP, University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - H Yamamoto
- ISSP, University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - M Matsunami
- UVSOR Facility, Institute for Molecular Science, Okazaki 444-8585, Japan.,Energy Materials Laboratory, Toyota Technological Institute, Nagoya 468-8511, Japan
| | - S Kimura
- UVSOR Facility, Institute for Molecular Science, Okazaki 444-8585, Japan.,Graduate School of Frontier Biosciences, Osaka University, Suita, Osaka 565-0871, Japan
| | - N Inami
- Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki 305-0801, Japan
| | - K Ono
- Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki 305-0801, Japan
| | - H Kumigashira
- Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki 305-0801, Japan
| | - S Nakatsuji
- ISSP, University of Tokyo, Kashiwa, Chiba 277-8581, Japan.,PRESTO, Japan Science and Technology Agency (JST), 4-1-8 Honcho Kawaguchi, Saitama 332-0012, Japan
| | - L Balents
- Kavli Institute for Theoretical Physics, Santa Barbara, California 93106, USA
| | - S Shin
- ISSP, University of Tokyo, Kashiwa, Chiba 277-8581, Japan
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11
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Ueda K, Fujioka J, Yang BJ, Shiogai J, Tsukazaki A, Nakamura S, Awaji S, Nagaosa N, Tokura Y. Magnetic Field-Induced Insulator-Semimetal Transition in a Pyrochlore Nd2Ir2O7. Phys Rev Lett 2015; 115:056402. [PMID: 26274430 DOI: 10.1103/physrevlett.115.056402] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/26/2015] [Indexed: 06/04/2023]
Abstract
We investigate magnetotransport properties in a single crystal of pyrochore-type Nd2Ir2O7. The metallic conduction is observed on the antiferromagnetic domain walls of the all-in-all-out-type Ir 5d moment ordered insulating bulk state that can be finely controlled by an external magnetic field along [111]. On the other hand, an applied field along [001] induces the bulk phase transition from insulator to semimetal as a consequence of the field-induced modification of the Nd 4f and Ir 5d moment configurations. A theoretical calculation consistently describing the experimentally observed features suggests a variety of exotic topological states as functions of electron correlation and Ir 5d moment orders, which can be finely tuned by the choice of rare-earth ion and magnetic field, respectively.
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Affiliation(s)
- K Ueda
- Department of Applied Physics and Quantum Phase Electronics Center, University of Tokyo, Tokyo 113-8656, Japan
| | - J Fujioka
- Department of Applied Physics and Quantum Phase Electronics Center, University of Tokyo, Tokyo 113-8656, Japan
| | - B-J Yang
- Center for Emergent Matter Science (CEMS), RIKEN Advanced Science Institute (ASI), Wako 351-0198, Japan
| | - J Shiogai
- Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
| | - A Tsukazaki
- Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
| | - S Nakamura
- Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
| | - S Awaji
- Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
| | - N Nagaosa
- Department of Applied Physics and Quantum Phase Electronics Center, University of Tokyo, Tokyo 113-8656, Japan
- Center for Emergent Matter Science (CEMS), RIKEN Advanced Science Institute (ASI), Wako 351-0198, Japan
| | - Y Tokura
- Department of Applied Physics and Quantum Phase Electronics Center, University of Tokyo, Tokyo 113-8656, Japan
- Center for Emergent Matter Science (CEMS), RIKEN Advanced Science Institute (ASI), Wako 351-0198, Japan
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12
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Udagawa M, Moessner R. Anomalous Hall effect from frustration-tuned scalar chirality distribution in Pr2Ir2O7. Phys Rev Lett 2013; 111:036602. [PMID: 23909347 DOI: 10.1103/physrevlett.111.036602] [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: 07/25/2012] [Indexed: 06/02/2023]
Abstract
We study the anomalous Hall effect due to noncoplanar magnetism on a pyrochlore structure. We focus on the frustration-induced spatial inhomogeneity of different magnetic low-temperature regimes, between which one can efficiently tune using an external magnetic field. We incorporate nonmagnetic scattering on a phenomenological level so that we can distinguish between the effects of short-range correlations and short-range coherence. We obtain a Hall conductivity (σ(H)) as a function of field strength and direction which compares well to the experimental data of Pr(2)Ir(2)O(7). In particular, we show that the observed peak in σ(H) for H[parallel][111] signals the crossover from zero-field spin ice to kagome ice.
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Affiliation(s)
- M Udagawa
- Department of Applied Physics, University of Tokyo, Tokyo 113-8656, Japan
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13
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Mokrousov Y, Zhang H, Freimuth F, Zimmermann B, Long NH, Weischenberg J, Souza I, Mavropoulos P, Blügel S. Anisotropy of spin relaxation and transverse transport in metals. J Phys Condens Matter 2013; 25:163201. [PMID: 23511040 DOI: 10.1088/0953-8984/25/16/163201] [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: 06/01/2023]
Abstract
Using first-principles methods we explore the anisotropy of the spin relaxation and transverse transport properties in bulk metals with respect to the real-space direction of the spin-quantization axis in paramagnets or of the spontaneous magnetization in ferromagnets. Owing to the presence of the spin-orbit coupling the orbital and spin character of the Bloch states depends sensitively on the orientation of the spins relative to the crystal axes. This leads to drastic changes in quantities which rely on interband mixing induced by the spin-orbit interaction. The anisotropy is particularly striking for quantities which exhibit spiky and irregular distributions in the Brillouin zone, such as the spin-mixing parameter or the Berry curvature of the electronic states. We demonstrate this for three cases: (i) the Elliott-Yafet spin-relaxation mechanism in paramagnets with structural inversion symmetry; (ii) the intrinsic anomalous Hall effect in ferromagnets; and (iii) the spin Hall effect in paramagnets. We discuss the consequences of the pronounced anisotropic behavior displayed by these properties for spin-polarized transport applications.
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Affiliation(s)
- Yuriy Mokrousov
- Peter Grünberg Institut and Institute for Advanced Simulation, Forschungszentrum Jülich and JARA, Jülich, Germany.
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14
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Udagawa M, Ishizuka H, Motome Y. Non-Kondo mechanism for resistivity minimum in spin ice conduction systems. Phys Rev Lett 2012; 108:066406. [PMID: 22401096 DOI: 10.1103/physrevlett.108.066406] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/03/2011] [Indexed: 05/31/2023]
Abstract
We present a mechanism of resistivity minimum in conduction electron systems coupled with localized moments, which is distinguished from the Kondo effect. Instead of the spin-flip process in the Kondo effect, electrons are elastically scattered by local spin correlations which evolve in a particular way under geometrical frustration as decreasing temperature. This is demonstrated by the cellular dynamical mean-field theory for a spin-ice-type Kondo lattice model on a pyrochlore lattice. Peculiar temperature dependences of the resistivity, specific heat, and magnetic susceptibility in the non-Kondo mechanism are compared with the experimental data in metallic Ir pyrochlore oxides.
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Affiliation(s)
- Masafumi Udagawa
- Department of Applied Physics, University of Tokyo, Tokyo, Japan
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