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Graham AJ, Park H, Nguyen PV, Nunn J, Kandyba V, Cattelan M, Giampietri A, Barinov A, Watanabe K, Taniguchi T, Andreev A, Rudner M, Xu X, Wilson NR, Cobden DH. Conduction Band Replicas in a 2D Moiré Semiconductor Heterobilayer. NANO LETTERS 2024; 24:5117-5124. [PMID: 38629940 DOI: 10.1021/acs.nanolett.3c04866] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2024]
Abstract
Stacking monolayer semiconductors creates moiré patterns, leading to correlated and topological electronic phenomena, but measurements of the electronic structure underpinning these phenomena are scarce. Here, we investigate the properties of the conduction band in moiré heterobilayers of WS2/WSe2 using submicrometer angle-resolved photoemission spectroscopy with electrostatic gating. We find that at all twist angles the conduction band edge is the K-point valley of the WS2, with a band gap of 1.58 ± 0.03 eV. From the resolved conduction band dispersion, we deduce an effective mass of 0.15 ± 0.02 me. Additionally, we observe replicas of the conduction band displaced by reciprocal lattice vectors of the moiré superlattice. We argue that the replicas result from the moiré potential modifying the conduction band states rather than final-state diffraction. Interestingly, the replicas display an intensity pattern with reduced 3-fold symmetry, which we show implicates the pseudo vector potential associated with in-plane strain in moiré band formation.
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Affiliation(s)
- Abigail J Graham
- Department of Physics, University of Warwick, Coventry CV4 7AL, U.K
| | - Heonjoon Park
- Department of Physics, University of Washington, Seattle, Washington 98195, United States
| | - Paul V Nguyen
- Department of Physics, University of Washington, Seattle, Washington 98195, United States
| | - James Nunn
- Department of Physics, University of Warwick, Coventry CV4 7AL, U.K
| | - Viktor Kandyba
- Elettra - Sincrotrone Trieste, S.C.p.A, Basovizza (TS), Friuli-Venezia Giulia 34149, Italy
| | - Mattia Cattelan
- Elettra - Sincrotrone Trieste, S.C.p.A, Basovizza (TS), Friuli-Venezia Giulia 34149, Italy
| | - Alessio Giampietri
- Elettra - Sincrotrone Trieste, S.C.p.A, Basovizza (TS), Friuli-Venezia Giulia 34149, Italy
| | - Alexei Barinov
- Elettra - Sincrotrone Trieste, S.C.p.A, Basovizza (TS), Friuli-Venezia Giulia 34149, Italy
| | - Kenji Watanabe
- Research Center for Electronic and Optical Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Takashi Taniguchi
- Research Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Anton Andreev
- Department of Physics, University of Washington, Seattle, Washington 98195, United States
| | - Mark Rudner
- Department of Physics, University of Washington, Seattle, Washington 98195, United States
| | - Xiaodong Xu
- Department of Physics, University of Washington, Seattle, Washington 98195, United States
- Department of Materials Science and Engineering, University of Washington, Seattle, Washington 98195, United States
| | - Neil R Wilson
- Department of Physics, University of Warwick, Coventry CV4 7AL, U.K
| | - David H Cobden
- Department of Physics, University of Washington, Seattle, Washington 98195, United States
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Nunn JE, McEllistrim A, Weston A, Garcia-Ruiz A, Watson MD, Mucha-Kruczynski M, Cacho C, Gorbachev RV, Fal'ko VI, Wilson NR. ARPES Signatures of Few-Layer Twistronic Graphenes. NANO LETTERS 2023. [PMID: 37235208 DOI: 10.1021/acs.nanolett.3c01173] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Diverse emergent correlated electron phenomena have been observed in twisted-graphene layers. Many electronic structure predictions have been reported exploring this new field, but with few momentum-resolved electronic structure measurements to test them. We use angle-resolved photoemission spectroscopy to study the twist-dependent (1° < θ < 8°) band structure of twisted-bilayer, monolayer-on-bilayer, and double-bilayer graphene (tDBG). Direct comparison is made between experiment and theory, using a hybrid k·p model for interlayer coupling. Quantitative agreement is found across twist angles, stacking geometries, and back-gate voltages, validating the models and revealing field-induced gaps in twisted graphenes. However, for tDBG at θ = 1.5 ± 0.2°, close to the magic angle θ = 1.3°, a flat band is found near the Fermi level with measured bandwidth Ew = 31 ± 5 meV. An analysis of the gap between the flat band and the next valence band shows deviations between experiment (Δh = 46 ± 5 meV) and theory (Δh = 5 meV), indicative of lattice relaxation in this regime.
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Affiliation(s)
- James E Nunn
- Diamond Light Source, Division of Science, Didcot OX11 0DE, U.K
- Department of Physics, University of Warwick, Coventry CV4 7AL, U.K
| | - Andrew McEllistrim
- School of Physics and Astronomy, University of Manchester, Oxford Road, Manchester M13 9PL, U.K
- National Graphene Institute, University of Manchester, Booth St East, Manchester M13 9PL, U.K
| | - Astrid Weston
- School of Physics and Astronomy, University of Manchester, Oxford Road, Manchester M13 9PL, U.K
- National Graphene Institute, University of Manchester, Booth St East, Manchester M13 9PL, U.K
| | - Aitor Garcia-Ruiz
- School of Physics and Astronomy, University of Manchester, Oxford Road, Manchester M13 9PL, U.K
- National Graphene Institute, University of Manchester, Booth St East, Manchester M13 9PL, U.K
| | | | - Marcin Mucha-Kruczynski
- Centre for Nanoscience and Nanotechnology, Department of Physics, University of Bath, Bath BA2 7AY, U.K
| | - Cephise Cacho
- Diamond Light Source, Division of Science, Didcot OX11 0DE, U.K
| | - Roman V Gorbachev
- School of Physics and Astronomy, University of Manchester, Oxford Road, Manchester M13 9PL, U.K
- National Graphene Institute, University of Manchester, Booth St East, Manchester M13 9PL, U.K
| | - Vladimir I Fal'ko
- School of Physics and Astronomy, University of Manchester, Oxford Road, Manchester M13 9PL, U.K
- National Graphene Institute, University of Manchester, Booth St East, Manchester M13 9PL, U.K
| | - Neil R Wilson
- Department of Physics, University of Warwick, Coventry CV4 7AL, U.K
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Franciosi A, Kiskinova M. Elettra-Sincrotrone Trieste: present and future. EUROPEAN PHYSICAL JOURNAL PLUS 2023; 138:79. [PMID: 36712550 PMCID: PMC9872737 DOI: 10.1140/epjp/s13360-023-03654-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/26/2022] [Accepted: 01/03/2023] [Indexed: 06/18/2023]
Abstract
We present an overview of the Elettra-Sincrotrone Trieste research center, which hosts synchrotron and free-electron laser light sources. We review the current status, provide examples of recent achievements in basic and applied research and discuss the upgrade programs of the facility.
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Affiliation(s)
- Alfonso Franciosi
- Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, 34149 Trieste, Italy
| | - Maya Kiskinova
- Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, 34149 Trieste, Italy
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