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Ali N, Singh B, Srivastava PK, Ali F, Lee M, Park H, Shin H, Lee K, Choi H, Lee S, Ngo TD, Hassan Y, Watanabe K, Taniguchi T, Lee C, Yoo WJ. Link between T-Linear Resistivity and Quantum Criticality in Ambipolar Black Phosphorus. ACS NANO 2024; 18:11978-11987. [PMID: 38652759 DOI: 10.1021/acsnano.4c02432] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/25/2024]
Abstract
The interplay between strong Coulomb interactions and kinetic energy leads to intricate many-body competing ground states owing to quantum fluctuations in 2D electron and hole gases. However, the simultaneous observation of quantum critical phenomena in both electron and hole regimes remains elusive. Here, we utilize anisotropic black phosphorus (BP) to show density-driven metal-insulator transition with a critical conductance ∼e2/h which highlights the significant role of quantum fluctuations in both hole and electron regimes. We observe a T-linear resistivity from the deep metallic phase to the metal-insulator boundary at moderate temperatures, while it turns to Fermi liquid behavior in the deep metallic phase at low temperatures in both regimes. An analysis of the resistivity suggests that disorder-dominated transport leads to T-linear behavior in the hole regime, while in the electron regime, the T-linear resistivity results from strong Coulomb interactions, suggestive of strange-metal behavior. Successful scaling collapse of the resistivity in the T-linear region demonstrates the link between quantum criticality and the T-linear resistivity in both regimes. Our study provides compelling evidence that ambipolar BP could serve as an exciting testbed for investigating exotic states and quantum critical phenomena in hole and electron regimes of 2D semiconductors.
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Affiliation(s)
- Nasir Ali
- SKKU Advanced Institute of Nano-Technology (SAINT), Sungkyunkwan University, 2066 Seobu-ro, Jangan-gu, Suwon, Gyeonggi-do 16419, Korea
| | - Budhi Singh
- School of Mechanical Engineering, Sungkyunkwan University, 2066 Seobu-ro, Jangan-gu, Suwon, Gyeonggi-do 16419, Korea
| | - Pawan Kumar Srivastava
- School of Mechanical Engineering, Sungkyunkwan University, 2066 Seobu-ro, Jangan-gu, Suwon, Gyeonggi-do 16419, Korea
| | - Fida Ali
- Department of Electronic and Nanoengineering, Aalto University, P.O. Box 13500, Aalto FI-00076, Finland
| | - Myeongjin Lee
- SKKU Advanced Institute of Nano-Technology (SAINT), Sungkyunkwan University, 2066 Seobu-ro, Jangan-gu, Suwon, Gyeonggi-do 16419, Korea
| | - Hyokwang Park
- SKKU Advanced Institute of Nano-Technology (SAINT), Sungkyunkwan University, 2066 Seobu-ro, Jangan-gu, Suwon, Gyeonggi-do 16419, Korea
| | - Hoseong Shin
- SKKU Advanced Institute of Nano-Technology (SAINT), Sungkyunkwan University, 2066 Seobu-ro, Jangan-gu, Suwon, Gyeonggi-do 16419, Korea
| | - Kwangro Lee
- SKKU Advanced Institute of Nano-Technology (SAINT), Sungkyunkwan University, 2066 Seobu-ro, Jangan-gu, Suwon, Gyeonggi-do 16419, Korea
| | - Hyungyu Choi
- SKKU Advanced Institute of Nano-Technology (SAINT), Sungkyunkwan University, 2066 Seobu-ro, Jangan-gu, Suwon, Gyeonggi-do 16419, Korea
| | - Sungwon Lee
- SKKU Advanced Institute of Nano-Technology (SAINT), Sungkyunkwan University, 2066 Seobu-ro, Jangan-gu, Suwon, Gyeonggi-do 16419, Korea
| | - Tien Dat Ngo
- SKKU Advanced Institute of Nano-Technology (SAINT), Sungkyunkwan University, 2066 Seobu-ro, Jangan-gu, Suwon, Gyeonggi-do 16419, Korea
| | - Yasir Hassan
- SKKU Advanced Institute of Nano-Technology (SAINT), Sungkyunkwan University, 2066 Seobu-ro, Jangan-gu, Suwon, Gyeonggi-do 16419, Korea
| | - Kenji Watanabe
- National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Takashi Taniguchi
- National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Changgu Lee
- SKKU Advanced Institute of Nano-Technology (SAINT), Sungkyunkwan University, 2066 Seobu-ro, Jangan-gu, Suwon, Gyeonggi-do 16419, Korea
- School of Mechanical Engineering, Sungkyunkwan University, 2066 Seobu-ro, Jangan-gu, Suwon, Gyeonggi-do 16419, Korea
| | - Won Jong Yoo
- SKKU Advanced Institute of Nano-Technology (SAINT), Sungkyunkwan University, 2066 Seobu-ro, Jangan-gu, Suwon, Gyeonggi-do 16419, Korea
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Yang C, Esin I, Lewandowski C, Refael G. Optical Control of Slow Topological Electrons in Moiré Systems. PHYSICAL REVIEW LETTERS 2023; 131:026901. [PMID: 37505954 DOI: 10.1103/physrevlett.131.026901] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/01/2023] [Revised: 05/17/2023] [Accepted: 06/13/2023] [Indexed: 07/30/2023]
Abstract
Floquet moiré materials possess optically-induced flat-electron bands with steady-states sensitive to drive parameters. Within this regime, we show that strong interaction screening and phonon bath coupling can overcome enhanced drive-induced heating. In twisted bilayer graphene (TBG) irradiated by a terahertz-frequency continuous circularly polarized laser, the extremely slow electronic states enable the drive to control the steady state occupation of high-Berry curvature electronic states. In particular, above a critical field amplitude, high-Berry-curvature states exhibit a slow regime where they decouple from acoustic phonons, allowing the drive to control the anomalous Hall response. Our work shows that the laser-induced control of topological and transport physics in Floquet TBG are measurable using experimentally available probes.
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Affiliation(s)
- Christopher Yang
- Department of Physics, IQIM, California Institute of Technology, Pasadena, California 91125, USA
| | - Iliya Esin
- Department of Physics, IQIM, California Institute of Technology, Pasadena, California 91125, USA
| | - Cyprian Lewandowski
- Department of Physics, IQIM, California Institute of Technology, Pasadena, California 91125, USA
- National High Magnetic Field Laboratory, Tallahassee, Florida 32310, USA
- Department of Physics, Florida State University, Tallahassee, Florida 32306, USA
| | - Gil Refael
- Department of Physics, IQIM, California Institute of Technology, Pasadena, California 91125, USA
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Esin I, Esterlis I, Demler E, Refael G. Generating Coherent Phonon Waves in Narrow-Band Materials: A Twisted Bilayer Graphene Phaser. PHYSICAL REVIEW LETTERS 2023; 130:147001. [PMID: 37084441 DOI: 10.1103/physrevlett.130.147001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/07/2022] [Accepted: 03/17/2023] [Indexed: 05/03/2023]
Abstract
Twisted bilayer graphene (TBG) exhibits extremely low Fermi velocities for electrons, with the speed of sound surpassing the Fermi velocity. This regime enables the use of TBG for amplifying vibrational waves of the lattice through stimulated emission, following the same principles of operation of free-electron lasers. Our Letter proposes a lasing mechanism relying on the slow-electron bands to produce a coherent beam of acoustic phonons. We propose a device based on undulated electrons in TBG, which we dub the phaser. The device generates phonon beams in a terahertz (THz) frequency range, which can then be used to produce THz electromagnetic radiation. The ability to generate coherent phonons in solids breaks new ground in controlling quantum memories, probing quantum states, realizing nonequilibrium phases of matter, and designing new types of THz optical devices.
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Affiliation(s)
- Iliya Esin
- Department of Physics and Institute for Quantum Information and Matter, California Institute of Technology, Pasadena, California 91125, USA
| | - Ilya Esterlis
- Department of Physics, Harvard University, Cambridge Massachusetts 02138, USA
| | - Eugene Demler
- Institute for Theoretical Physics, ETH Zurich, 8093 Zurich, Switzerland
| | - Gil Refael
- Department of Physics and Institute for Quantum Information and Matter, California Institute of Technology, Pasadena, California 91125, USA
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Liu X, Peng R, Sun Z, Liu J. Moiré Phonons in Magic-Angle Twisted Bilayer Graphene. NANO LETTERS 2022; 22:7791-7797. [PMID: 36170965 PMCID: PMC9562463 DOI: 10.1021/acs.nanolett.2c02010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/18/2022] [Revised: 09/11/2022] [Indexed: 06/16/2023]
Abstract
Magic-angle twisted bilayer graphene (TBG) has attracted significant interest recently due to the discoveries of diverse correlated and topological states. In this work, we study the phonon properties in magic-angle TBG based on many-body classical potential and interatomic forces generated by a deep neural network trained with data from ab initio calculations. We have discovered a number of soft modes which can exhibit dipolar, quadrupolar, and octupolar vibrational patterns in real space, as well as some time-reversal breaking chiral phonon modes. We have further studied the phonon effects on the electronic structures by freezing certain soft phonon modes. We find that if a soft quadrupolar phonon mode is assumed to be frozen, the system would exhibit a charge order which is perfectly consistent with recent experiments. Moreover, once some low-frequency C2z-breaking modes get frozen, the Dirac points at the charge neutrality point would be gapped out, which provides an alternative perspective to the origin of correlated insulator state at charge neutrality point.
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Affiliation(s)
- Xiaoqian Liu
- School
of Physical Science and Technology, ShanghaiTech
University, Shanghai 201210, China
| | - Ran Peng
- School
of Physical Science and Technology, ShanghaiTech
University, Shanghai 201210, China
| | - Zhaoru Sun
- School
of Physical Science and Technology, ShanghaiTech
University, Shanghai 201210, China
| | - Jianpeng Liu
- School
of Physical Science and Technology, ShanghaiTech
University, Shanghai 201210, China
- ShanghaiTech
Laboratory for Topological Physics, ShanghaiTech
University, Shanghai 201210, China
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Cha P, Patel AA, Kim EA. Strange Metals from Melting Correlated Insulators in Twisted Bilayer Graphene. PHYSICAL REVIEW LETTERS 2021; 127:266601. [PMID: 35029498 DOI: 10.1103/physrevlett.127.266601] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/02/2021] [Revised: 09/24/2021] [Accepted: 11/01/2021] [Indexed: 06/14/2023]
Abstract
Even as the understanding of the mechanism behind correlated insulating states in magic-angle twisted bilayer graphene converges toward various kinds of spontaneous symmetry breaking, the metallic "normal state" above the insulating transition temperature remains mysterious, with its excessively high entropy and linear-in-temperature resistivity. In this Letter, we focus on the effects of fluctuations of the order parameters describing correlated insulating states at integer fillings of the low-energy flat bands on charge transport. Motivated by the observation of heterogeneity in the order-parameter landscape at zero magnetic field in certain samples, we conjecture the existence of frustrating extended-range interactions in an effective Ising model of the order parameters on a triangular lattice. The competition between short-distance ferromagnetic interactions and frustrating extended-range antiferromagnetic interactions leads to an emergent length scale that forms stripy mesoscale domains above the ordering transition. The gapless fluctuations of these heterogeneous configurations are found to be responsible for the linear-in-temperature resistivity as well as the enhanced low-temperature entropy. Our insights link experimentally observed linear-in-temperature resistivity and enhanced entropy to the strength of frustration or, equivalently, to the emergence of mesoscopic length scales characterizing order-parameter domains.
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Affiliation(s)
- Peter Cha
- Department of Physics, Cornell University, Ithaca, New York 14853, USA
| | - Aavishkar A Patel
- Department of Physics, University of California, Berkeley, California 94720, USA
| | - Eun-Ah Kim
- Department of Physics, Cornell University, Ithaca, New York 14853, USA
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