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Title: Emergence of Interfacial Polarons from Electron–Phonon Coupling in Graphene/h-BN van der Waals Heterostructures

Abstract

van der Waals heterostructures, vertical stacks of layered materials, offer new opportunities for novel quantum phenomena which are absent in their constituent components. Here we report the emergence of polaron quasiparticles at the interface of graphene/hexagonal boron nitride (h-BN) heterostructures. Using nanospot angle-resolved photoemission spectroscopy, we observe zone-corner replicas of h-BN valence band maxima, with energy spacing coincident with the highest phonon energy of the heterostructure, an indication of Fröhlich polaron formation due to forward-scattering electron–phonon coupling. Parabolic fitting of the h-BN bands yields an effective mass enhancement of ~2.3, suggesting an intermediate coupling strength. Our theoretical simulations based on Migdal–Eliashberg theory corroborate the experimental results, allowing the extraction of microscopic physical parameters. Moreover, renormalization of graphene π-band is observed due to the hybridization with the h-BN band. Lastly, our work generalizes the polaron study from transition metal oxides to van der Waals heterostructures with higher material flexibility, highlighting interlayer coupling as an extra degree of freedom to explore emergent phenomena.

Authors:
ORCiD logo [1];  [1];  [2];  [3];  [4];  [2];  [2];  [5];  [6];  [2];  [1]
  1. Synchrotron SOLEIL and Univ. Paris-Saclay, Gif sur Yvette Cedex (France)
  2. Chinese Academy of Sciences (CAS), Beijing (China)
  3. Stanford Univ., Stanford, CA (United States); SLAC National Accelerator Lab., Menlo Park, CA (United States)
  4. Univ. of Bath, Bath (United Kingdom)
  5. Chinese Academy of Sciences (CAS), Beijing (China); SLAC National Accelerator Lab., Menlo Park, CA (United States)
  6. SLAC National Accelerator Lab., Menlo Park, CA (United States); Stanford Univ., Stanford, CA (United States)
Publication Date:
Research Org.:
SLAC National Accelerator Lab., Menlo Park, CA (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). National Energy Research Scientific Computing Center
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22); USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22). Materials Sciences & Engineering Division
OSTI Identifier:
1461624
Alternate Identifier(s):
OSTI ID: 1484748
Grant/Contract Number:  
2013CB934500; AC02-76SF00515; 61325021; AC02-05CH11231
Resource Type:
Accepted Manuscript
Journal Name:
Nano Letters
Additional Journal Information:
Journal Volume: 18; Journal Issue: 2; Journal ID: ISSN 1530-6984
Publisher:
American Chemical Society
Country of Publication:
United States
Language:
English
Subject:
77 NANOSCIENCE AND NANOTECHNOLOGY; electronic structure; electron−phonon coupling; Migdal-Eliashberg theory; NanoARPES; polaron; van der Waals heterostructure

Citation Formats

Chen, Chaoyu, Avila, Jose, Wang, Shuopei, Wang, Yao, Mucha-Kruczy?ski, Marcin, Shen, Cheng, Yang, Rong, Nosarzewski, Benjamin, Devereaux, Thomas P., Zhang, Guangyu, and Asensio, Maria Carmen. Emergence of Interfacial Polarons from Electron–Phonon Coupling in Graphene/h-BN van der Waals Heterostructures. United States: N. p., 2018. Web. doi:10.1021/acs.nanolett.7b04604.
Chen, Chaoyu, Avila, Jose, Wang, Shuopei, Wang, Yao, Mucha-Kruczy?ski, Marcin, Shen, Cheng, Yang, Rong, Nosarzewski, Benjamin, Devereaux, Thomas P., Zhang, Guangyu, & Asensio, Maria Carmen. Emergence of Interfacial Polarons from Electron–Phonon Coupling in Graphene/h-BN van der Waals Heterostructures. United States. doi:10.1021/acs.nanolett.7b04604.
Chen, Chaoyu, Avila, Jose, Wang, Shuopei, Wang, Yao, Mucha-Kruczy?ski, Marcin, Shen, Cheng, Yang, Rong, Nosarzewski, Benjamin, Devereaux, Thomas P., Zhang, Guangyu, and Asensio, Maria Carmen. Fri . "Emergence of Interfacial Polarons from Electron–Phonon Coupling in Graphene/h-BN van der Waals Heterostructures". United States. doi:10.1021/acs.nanolett.7b04604. https://www.osti.gov/servlets/purl/1461624.
@article{osti_1461624,
title = {Emergence of Interfacial Polarons from Electron–Phonon Coupling in Graphene/h-BN van der Waals Heterostructures},
author = {Chen, Chaoyu and Avila, Jose and Wang, Shuopei and Wang, Yao and Mucha-Kruczy?ski, Marcin and Shen, Cheng and Yang, Rong and Nosarzewski, Benjamin and Devereaux, Thomas P. and Zhang, Guangyu and Asensio, Maria Carmen},
abstractNote = {van der Waals heterostructures, vertical stacks of layered materials, offer new opportunities for novel quantum phenomena which are absent in their constituent components. Here we report the emergence of polaron quasiparticles at the interface of graphene/hexagonal boron nitride (h-BN) heterostructures. Using nanospot angle-resolved photoemission spectroscopy, we observe zone-corner replicas of h-BN valence band maxima, with energy spacing coincident with the highest phonon energy of the heterostructure, an indication of Fröhlich polaron formation due to forward-scattering electron–phonon coupling. Parabolic fitting of the h-BN bands yields an effective mass enhancement of ~2.3, suggesting an intermediate coupling strength. Our theoretical simulations based on Migdal–Eliashberg theory corroborate the experimental results, allowing the extraction of microscopic physical parameters. Moreover, renormalization of graphene π-band is observed due to the hybridization with the h-BN band. Lastly, our work generalizes the polaron study from transition metal oxides to van der Waals heterostructures with higher material flexibility, highlighting interlayer coupling as an extra degree of freedom to explore emergent phenomena.},
doi = {10.1021/acs.nanolett.7b04604},
journal = {Nano Letters},
number = 2,
volume = 18,
place = {United States},
year = {2018},
month = {1}
}

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