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Moore SL, Ciccarino CJ, Halbertal D, McGilly LJ, Finney NR, Yao K, Shao Y, Ni G, Sternbach A, Telford EJ, Kim BS, Rossi SE, Watanabe K, Taniguchi T, Pasupathy AN, Dean CR, Hone J, Schuck PJ, Narang P, Basov DN. Nanoscale lattice dynamics in hexagonal boron nitride moiré superlattices. Nat Commun 2021; 12:5741. [PMID: 34593793 PMCID: PMC8484559 DOI: 10.1038/s41467-021-26072-7] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [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: 04/10/2021] [Accepted: 09/02/2021] [Indexed: 11/12/2022] Open
Abstract
Twisted two-dimensional van der Waals (vdW) heterostructures have unlocked a new means for manipulating the properties of quantum materials. The resulting mesoscopic moiré superlattices are accessible to a wide variety of scanning probes. To date, spatially-resolved techniques have prioritized electronic structure visualization, with lattice response experiments only in their infancy. Here, we therefore investigate lattice dynamics in twisted layers of hexagonal boron nitride (hBN), formed by a minute twist angle between two hBN monolayers assembled on a graphite substrate. Nano-infrared (nano-IR) spectroscopy reveals systematic variations of the in-plane optical phonon frequencies amongst the triangular domains and domain walls in the hBN moiré superlattices. Our first-principles calculations unveil a local and stacking-dependent interaction with the underlying graphite, prompting symmetry-breaking between the otherwise identical neighboring moiré domains of twisted hBN. Here, the authors investigate the lattice dynamics of twisted hexagonal boron nitride layers via nano-infrared spectroscopy, showing local and stacking-dependent variations of the optical phonon frequencies associated to the interaction with the graphite substrate.
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Affiliation(s)
- S L Moore
- Department of Physics, Columbia University, New York, NY, USA.
| | - C J Ciccarino
- John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA
| | - D Halbertal
- Department of Physics, Columbia University, New York, NY, USA
| | - L J McGilly
- Department of Physics, Columbia University, New York, NY, USA
| | - N R Finney
- Department of Mechanical Engineering, Columbia University, New York, NY, USA
| | - K Yao
- Department of Mechanical Engineering, Columbia University, New York, NY, USA
| | - Y Shao
- Department of Physics, Columbia University, New York, NY, USA
| | - G Ni
- Department of Physics, Columbia University, New York, NY, USA
| | - A Sternbach
- Department of Physics, Columbia University, New York, NY, USA
| | - E J Telford
- Department of Physics, Columbia University, New York, NY, USA
| | - B S Kim
- Department of Mechanical Engineering, Columbia University, New York, NY, USA
| | - S E Rossi
- Department of Physics, Columbia University, New York, NY, USA
| | - K Watanabe
- National Institute for Materials Science, 1-1 Namiki, Tsukuba, Japan
| | - T Taniguchi
- National Institute for Materials Science, 1-1 Namiki, Tsukuba, Japan
| | - A N Pasupathy
- Department of Physics, Columbia University, New York, NY, USA
| | - C R Dean
- Department of Physics, Columbia University, New York, NY, USA
| | - J Hone
- Department of Mechanical Engineering, Columbia University, New York, NY, USA
| | - P J Schuck
- Department of Mechanical Engineering, Columbia University, New York, NY, USA
| | - P Narang
- John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA
| | - D N Basov
- Department of Physics, Columbia University, New York, NY, USA
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Sunku SS, Halbertal D, Stauber T, Chen S, McLeod AS, Rikhter A, Berkowitz ME, Lo CFB, Gonzalez-Acevedo DE, Hone JC, Dean CR, Fogler MM, Basov DN. Hyperbolic enhancement of photocurrent patterns in minimally twisted bilayer graphene. Nat Commun 2021; 12:1641. [PMID: 33712611 PMCID: PMC7955135 DOI: 10.1038/s41467-021-21792-2] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2020] [Accepted: 02/11/2021] [Indexed: 11/18/2022] Open
Abstract
Quasi-periodic moiré patterns and their effect on electronic properties of twisted bilayer graphene have been intensely studied. At small twist angle θ, due to atomic reconstruction, the moiré superlattice morphs into a network of narrow domain walls separating micron-scale AB and BA stacking regions. We use scanning probe photocurrent imaging to resolve nanoscale variations of the Seebeck coefficient occurring at these domain walls. The observed features become enhanced in a range of mid-infrared frequencies where the hexagonal boron nitride substrate is optically hyperbolic. Our results illustrate the capabilities of the nano-photocurrent technique for probing nanoscale electronic inhomogeneities in two-dimensional materials.
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Affiliation(s)
- S S Sunku
- Department of Physics, Columbia University, New York, NY, 10027, USA
- Department of Applied Physics and Applied Mathematics, Columbia University, New York, NY, 10027, USA
| | - D Halbertal
- Department of Physics, Columbia University, New York, NY, 10027, USA.
| | - T Stauber
- Departamento de Teoría y Simulación de Materiales, Instituto de Ciencia de Materiales de Madrid, CSIC, Madrid, 28049, Spain
| | - S Chen
- Department of Physics, Columbia University, New York, NY, 10027, USA
| | - A S McLeod
- Department of Physics, Columbia University, New York, NY, 10027, USA
| | - A Rikhter
- Department of Physics, University of California, San Diego, La Jolla, CA, 92093, USA
| | - M E Berkowitz
- Department of Physics, Columbia University, New York, NY, 10027, USA
| | - C F B Lo
- Department of Physics, Columbia University, New York, NY, 10027, USA
| | | | - J C Hone
- Department of Mechanical Engineering, Columbia University, New York, NY, 10027, USA
| | - C R Dean
- Department of Physics, Columbia University, New York, NY, 10027, USA
| | - M M Fogler
- Department of Physics, University of California, San Diego, La Jolla, CA, 92093, USA
| | - D N Basov
- Department of Physics, Columbia University, New York, NY, 10027, USA
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Marguerite A, Birkbeck J, Aharon-Steinberg A, Halbertal D, Bagani K, Marcus I, Myasoedov Y, Geim AK, Perello DJ, Zeldov E. Publisher Correction: Imaging work and dissipation in the quantum Hall state in graphene. Nature 2019; 576:E6. [DOI: 10.1038/s41586-019-1823-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Embon L, Anahory Y, Suhov A, Halbertal D, Cuppens J, Yakovenko A, Uri A, Myasoedov Y, Rappaport ML, Huber ME, Gurevich A, Zeldov E. Probing dynamics and pinning of single vortices in superconductors at nanometer scales. Sci Rep 2015; 5:7598. [PMID: 25564043 PMCID: PMC4288220 DOI: 10.1038/srep07598] [Citation(s) in RCA: 65] [Impact Index Per Article: 7.2] [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: 10/03/2014] [Accepted: 12/03/2014] [Indexed: 11/08/2022] Open
Abstract
The dynamics of quantized magnetic vortices and their pinning by materials defects determine electromagnetic properties of superconductors, particularly their ability to carry non-dissipative currents. Despite recent advances in the understanding of the complex physics of vortex matter, the behavior of vortices driven by current through a multi-scale potential of the actual materials defects is still not well understood, mostly due to the scarcity of appropriate experimental tools capable of tracing vortex trajectories on nanometer scales. Using a novel scanning superconducting quantum interference microscope we report here an investigation of controlled dynamics of vortices in lead films with sub-Angstrom spatial resolution and unprecedented sensitivity. We measured, for the first time, the fundamental dependence of the elementary pinning force of multiple defects on the vortex displacement, revealing a far more complex behavior than has previously been recognized, including striking spring softening and broken-spring depinning, as well as spontaneous hysteretic switching between cellular vortex trajectories. Our results indicate the importance of thermal fluctuations even at 4.2 K and of the vital role of ripples in the pinning potential, giving new insights into the mechanisms of magnetic relaxation and electromagnetic response of superconductors.
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Affiliation(s)
- L. Embon
- Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot, 7610001, Israel
| | - Y. Anahory
- Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot, 7610001, Israel
| | - A. Suhov
- Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot, 7610001, Israel
| | - D. Halbertal
- Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot, 7610001, Israel
| | - J. Cuppens
- Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot, 7610001, Israel
| | - A. Yakovenko
- Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot, 7610001, Israel
| | - A. Uri
- Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot, 7610001, Israel
| | - Y. Myasoedov
- Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot, 7610001, Israel
| | - M. L. Rappaport
- Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot, 7610001, Israel
| | - M. E. Huber
- Department of Physics, University of Colorado Denver, Denver, 80217, USA
| | - A. Gurevich
- Department of Physics, Old Dominion University, Norfolk, VA 23529-0116, USA
| | - E. Zeldov
- Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot, 7610001, Israel
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