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Karni O, Barré E, Pareek V, Georgaras JD, Man MKL, Sahoo C, Bacon DR, Zhu X, Ribeiro HB, O'Beirne AL, Hu J, Al-Mahboob A, Abdelrasoul MMM, Chan NS, Karmakar A, Winchester AJ, Kim B, Watanabe K, Taniguchi T, Barmak K, Madéo J, da Jornada FH, Heinz TF, Dani KM. Structure of the moiré exciton captured by imaging its electron and hole. Nature 2022; 603:247-252. [PMID: 35264760 DOI: 10.1038/s41586-021-04360-y] [Citation(s) in RCA: 20] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2021] [Accepted: 12/14/2021] [Indexed: 11/09/2022]
Abstract
Interlayer excitons (ILXs) - electron-hole pairs bound across two atomically thin layered semiconductors - have emerged as attractive platforms to study exciton condensation1-4, single-photon emission and other quantum information applications5-7. Yet, despite extensive optical spectroscopic investigations8-12, critical information about their size, valley configuration and the influence of the moiré potential remains unknown. Here, in a WSe2/MoS2 heterostructure, we captured images of the time-resolved and momentum-resolved distribution of both of the particles that bind to form the ILX: the electron and the hole. We thereby obtain a direct measurement of both the ILX diameter of around 5.2 nm, comparable with the moiré-unit-cell length of 6.1 nm, and the localization of its centre of mass. Surprisingly, this large ILX is found pinned to a region of only 1.8 nm diameter within the moiré cell, smaller than the size of the exciton itself. This high degree of localization of the ILX is backed by Bethe-Salpeter equation calculations and demonstrates that the ILX can be localized within small moiré unit cells. Unlike large moiré cells, these are uniform over large regions, allowing the formation of extended arrays of localized excitations for quantum technology.
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Affiliation(s)
- Ouri Karni
- Department of Applied Physics, Stanford University, Stanford, CA, USA.,SLAC National Accelerator Laboratory, Menlo Park, CA, USA
| | - Elyse Barré
- SLAC National Accelerator Laboratory, Menlo Park, CA, USA.,Department of Electrical Engineering, Stanford University, Stanford, CA, USA
| | - Vivek Pareek
- Femtosecond Spectroscopy Unit, Okinawa Institute of Science and Technology Graduate University, Onna-son, Okinawa, Japan
| | - Johnathan D Georgaras
- Department of Materials Science and Engineering, Stanford University, Stanford, CA, USA
| | - Michael K L Man
- Femtosecond Spectroscopy Unit, Okinawa Institute of Science and Technology Graduate University, Onna-son, Okinawa, Japan
| | - Chakradhar Sahoo
- Femtosecond Spectroscopy Unit, Okinawa Institute of Science and Technology Graduate University, Onna-son, Okinawa, Japan.,Tata Institute of Fundamental Research, Hyderabad, Gopanpally, Serlingampalli, Telangana, India
| | - David R Bacon
- Femtosecond Spectroscopy Unit, Okinawa Institute of Science and Technology Graduate University, Onna-son, Okinawa, Japan
| | - Xing Zhu
- Femtosecond Spectroscopy Unit, Okinawa Institute of Science and Technology Graduate University, Onna-son, Okinawa, Japan
| | | | - Aidan L O'Beirne
- SLAC National Accelerator Laboratory, Menlo Park, CA, USA.,Department of Physics, Stanford University, Stanford, CA, USA
| | - Jenny Hu
- Department of Applied Physics, Stanford University, Stanford, CA, USA
| | - Abdullah Al-Mahboob
- Femtosecond Spectroscopy Unit, Okinawa Institute of Science and Technology Graduate University, Onna-son, Okinawa, Japan
| | - Mohamed M M Abdelrasoul
- Femtosecond Spectroscopy Unit, Okinawa Institute of Science and Technology Graduate University, Onna-son, Okinawa, Japan
| | - Nicholas S Chan
- Femtosecond Spectroscopy Unit, Okinawa Institute of Science and Technology Graduate University, Onna-son, Okinawa, Japan
| | - Arka Karmakar
- Femtosecond Spectroscopy Unit, Okinawa Institute of Science and Technology Graduate University, Onna-son, Okinawa, Japan
| | - Andrew J Winchester
- Femtosecond Spectroscopy Unit, Okinawa Institute of Science and Technology Graduate University, Onna-son, Okinawa, Japan
| | - Bumho Kim
- Department of Mechanical Engineering, Columbia University, New York, NY, USA
| | - Kenji Watanabe
- Research Center for Functional Materials, National Institute for Materials Science, Tsukuba, Japan
| | - Takashi Taniguchi
- International Center for Materials Nanoarchitectonics, National Institute for Materials Science, Tsukuba, Japan
| | - Katayun Barmak
- Department of Applied Physics and Applied Mathematics, Columbia University, New York, NY, USA
| | - Julien Madéo
- Femtosecond Spectroscopy Unit, Okinawa Institute of Science and Technology Graduate University, Onna-son, Okinawa, Japan
| | - Felipe H da Jornada
- Department of Materials Science and Engineering, Stanford University, Stanford, CA, USA
| | - Tony F Heinz
- Department of Applied Physics, Stanford University, Stanford, CA, USA.,SLAC National Accelerator Laboratory, Menlo Park, CA, USA
| | - Keshav M Dani
- Femtosecond Spectroscopy Unit, Okinawa Institute of Science and Technology Graduate University, Onna-son, Okinawa, Japan.
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Chen P, Atallah TL, Lin Z, Wang P, Lee SJ, Xu J, Huang Z, Duan X, Ping Y, Huang Y, Caram JR, Duan X. Approaching the intrinsic exciton physics limit in two-dimensional semiconductor diodes. Nature 2021; 599:404-410. [PMID: 34789906 DOI: 10.1038/s41586-021-03949-7] [Citation(s) in RCA: 25] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2021] [Accepted: 08/24/2021] [Indexed: 11/09/2022]
Abstract
Two-dimensional (2D) semiconductors have attracted intense interest for their unique photophysical properties, including large exciton binding energies and strong gate tunability, which arise from their reduced dimensionality1-5. Despite considerable efforts, a disconnect persists between the fundamental photophysics in pristine 2D semiconductors and the practical device performances, which are often plagued by many extrinsic factors, including chemical disorder at the semiconductor-contact interface. Here, by using van der Waals contacts with minimal interfacial disorder, we suppress contact-induced Shockley-Read-Hall recombination and realize nearly intrinsic photophysics-dictated device performance in 2D semiconductor diodes. Using an electrostatic field in a split-gate geometry to independently modulate electron and hole doping in tungsten diselenide diodes, we discover an unusual peak in the short-circuit photocurrent at low charge densities. Time-resolved photoluminescence reveals a substantial decrease of the exciton lifetime from around 800 picoseconds in the charge-neutral regime to around 50 picoseconds at high doping densities owing to increased exciton-charge Auger recombination. Taken together, we show that an exciton-diffusion-limited model well explains the charge-density-dependent short-circuit photocurrent, a result further confirmed by scanning photocurrent microscopy. We thus demonstrate the fundamental role of exciton diffusion and two-body exciton-charge Auger recombination in 2D devices and highlight that the intrinsic photophysics of 2D semiconductors can be used to create more efficient optoelectronic devices.
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Affiliation(s)
- Peng Chen
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, CA, USA
| | - Timothy L Atallah
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, CA, USA
| | - Zhaoyang Lin
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, CA, USA
| | - Peiqi Wang
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, CA, USA
| | - Sung-Joon Lee
- Department of Materials Science and Engineering, University of California, Los Angeles, Los Angeles, CA, USA
| | - Junqing Xu
- Department of Chemistry and Biochemistry, University of California Santa Cruz, Santa Cruz, CA, USA
| | - Zhihong Huang
- Department of Materials Science and Engineering, University of California, Los Angeles, Los Angeles, CA, USA
| | - Xidong Duan
- State Key Laboratory for Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha, China
| | - Yuan Ping
- Department of Chemistry and Biochemistry, University of California Santa Cruz, Santa Cruz, CA, USA
| | - Yu Huang
- Department of Materials Science and Engineering, University of California, Los Angeles, Los Angeles, CA, USA.,California NanoSystems Institute, University of California, Los Angeles, Los Angeles, CA, USA
| | - Justin R Caram
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, CA, USA. .,California NanoSystems Institute, University of California, Los Angeles, Los Angeles, CA, USA.
| | - Xiangfeng Duan
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, CA, USA. .,California NanoSystems Institute, University of California, Los Angeles, Los Angeles, CA, USA.
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Wang L, Ennis M, Szabó G, Armstrong WE. Characteristics of GABAergic and cholinergic neurons in perinuclear zone of mouse supraoptic nucleus. J Neurophysiol 2014; 113:754-67. [PMID: 25376783 DOI: 10.1152/jn.00561.2014] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The perinuclear zone (PNZ) of the supraoptic nucleus (SON) contains some GABAergic and cholinergic neurons thought to innervate the SON proper. In mice expressing enhanced green fluorescent protein (eGFP) in association with glutamate decarboxylase (GAD)65 we found an abundance of GAD65-eGFP neurons in the PNZ, whereas in mice expressing GAD67-eGFP, there were few labeled PNZ neurons. In mice expressing choline acetyltransferase (ChAT)-eGFP, large, brightly fluorescent and small, dimly fluorescent ChAT-eGFP neurons were present in the PNZ. The small ChAT-eGFP and GAD65-eGFP neurons exhibited a low-threshold depolarizing potential consistent with a low-threshold spike, with little transient outward rectification. Large ChAT-eGFP neurons exhibited strong transient outward rectification and a large hyperpolarizing spike afterpotential, very similar to that of magnocellular vasopressin and oxytocin neurons. Thus the large soma and transient outward rectification of large ChAT-eGFP neurons suggest that these neurons would be difficult to distinguish from magnocellular SON neurons in dissociated preparations by these criteria. Large, but not small, ChAT-eGFP neurons were immunostained with ChAT antibody (AB144p). Reconstructed neurons revealed a few processes encroaching near and passing through the SON from all types but no clear evidence of a terminal axon arbor. Large ChAT-eGFP neurons were usually oriented vertically and had four or five dendrites with multiple branches and an axon with many collaterals and local arborizations. Small ChAT-eGFP neurons had a more restricted dendritic tree compared with parvocellular GAD65 neurons, the latter of which had long thin processes oriented mediolaterally. Thus many of the characteristics found previously in unidentified, small PNZ neurons are also found in identified GABAergic neurons and in a population of smaller ChAT-eGFP neurons.
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Affiliation(s)
- Lie Wang
- Department of Anatomy and Neurobiology and Neuroscience Institute, University of Tennessee Health Science Center, Memphis, Tennessee; and
| | - Matthew Ennis
- Department of Anatomy and Neurobiology and Neuroscience Institute, University of Tennessee Health Science Center, Memphis, Tennessee; and
| | - Gábor Szabó
- Department of Gene Technology and Developmental Biology, Institute of Experimental Medicine, Budapest, Hungary
| | - William E Armstrong
- Department of Anatomy and Neurobiology and Neuroscience Institute, University of Tennessee Health Science Center, Memphis, Tennessee; and
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Armstrong WE, Stern JE. Electrophysiological and morphological characteristics of neurons in perinuclear zone of supraoptic nucleus. J Neurophysiol 1997; 78:2427-37. [PMID: 9356394 DOI: 10.1152/jn.1997.78.5.2427] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Electrophysiological and morphological characteristics of neurons in perinuclear zone of supraoptic nucleus. J. Neurophysiol. 78: 2427-2437, 1997. Neurons in the perinuclear zone (PZ) of the supraoptic nucleus (SON) are thought to serve as interneurons and may mediate changes in neurohypophysial hormone release in response to physiological changes in blood pressure. However, the morphology and electrophysiological characteristics of PZ neurons are unknown. In the present study, PZ neurons from male and female rats were recorded intracellularly to determine some membrane properties, then filled with biocytin or biotinamide for morphological analysis. In general, PZ neurons had faster spikes than magnocellular SON neurons, and the great majority were characterized by a subthreshold depolarizing hump when depolarized from a hyperpolarized (less than -80 mV) membrane potential. In most neurons, this hump was similar to low-threshold spikes described in other CNS regions. Near-threshold, fast action potentials were clustered near the onset of these depolarizations. Conspicuously absent in all PZ neurons was the strong transient and subthreshold outward rectification characteristic of vasopressin and oxytocin neurons of the SON. These results suggest that PZ neurons are electrophysiologically distinct from neurosecretory neurons of the SON. No differences were found between male and female rats in any of the basic properties examined, including input resistance, membrane time constant, spike height, spike width, spike threshold, and the size of the spike afterhyperpolarization. Morphologically, PZ neurons were diverse but were divided into spiny and aspiny groups. Three spiny neurons and one aspiny neuron contributed an axonal projection to the SON characterized by varicosities suggestive of terminals. In the case of the three spiny neurons, the SON projection was clearly a minor collateral projection. The axon arborized in the PZ, but one or more branches were cut at the edge of the explant, indicating a longer projection. In the remaining neurons, no axonal projection to the SON was detected and several had axons leaving the explant. Some portion of the dendritic tree penetrated the SON in several neurons. The morphology of PZ neurons was thus heterogeneous and suggests that, for some cells at least, the projection to the SON may be a minor collateral component of a much wider axonal projection.
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Affiliation(s)
- W E Armstrong
- Department of Anatomy and Neurobiology, College of Medicine, University of Tennessee, Memphis, Tennessee 38163, USA
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