Ultrafast Umklapp-assisted electron-phonon cooling in magic-angle twisted bilayer graphene
Mehew, Jake Dudley (Institut Català de Nanociència i Nanotecnologia)
Luque Merino, Rafael (Institut de Ciències Fotòniques)
Ishizuka, Hiroaki (Tokyo Institute of Technology. Department of Physics)
Block, Alexander (Institut Català de Nanociència i Nanotecnologia)
Díez Mérida, Jaime (Institut de Ciències Fotòniques)
Díez Carlón, Andrés (Institut de Ciències Fotòniques)
Watanabe, Kenji (National Institute for Material Sciences)
Taniguchi, Takashi (National Institute for Material Sciences)
Levitov, Leonid S. (Massachusetts Institute of Technology)
Efetov, Dmitri K. (Munich Center for Quantum Science and Technology)
Tielrooij, Klaas-Jan (Institut Català de Nanociència i Nanotecnologia)

Date:	2024
Abstract:	Understanding electron-phonon interactions is fundamentally important and has crucial implications for device applications. However, in twisted bilayer graphene near the magic angle, this understanding is currently lacking. Here, we study electron-phonon coupling using time- and frequency-resolved photovoltage measurements as direct and complementary probes of phonon-mediated hot-electron cooling. We find a remarkable speedup in cooling of twisted bilayer graphene near the magic angle: The cooling time is a few picoseconds from room temperature down to 5 kelvin, whereas in pristine bilayer graphene, cooling to phonons becomes much slower for lower temperatures. Our experimental and theoretical analysis indicates that this ultrafast cooling is a combined effect of superlattice formation with low-energy moiré phonons, spatially compressed electronic Wannier orbitals, and a reduced superlattice Brillouin zone. This enables efficient electron-phonon Umklapp scattering that overcomes electron-phonon momentum mismatch. These results establish twist angle as an effective way to control energy relaxation and electronic heat flow.
Grants:	Agencia Estatal de Investigación SEV-2017-0706 "la Caixa" Foundation 100010434 European Commission 804349 Agencia Estatal de Investigación RYC-2017-22330 Agencia Estatal de Investigación PID2019-111673GB-I00 Agencia Estatal de Investigación PCI2021-122101-2A
Rights:	Aquest document està subjecte a una llicència d'ús Creative Commons. Es permet la reproducció total o parcial, la distribució, la comunicació pública de l'obra i la creació d'obres derivades, fins i tot amb finalitats comercials, sempre i quan es reconegui l'autoria de l'obra original.
Language:	Anglès
Document:	Article ; recerca ; Versió publicada
Subject:	Bilayer Graphene ; Device application ; Electron phonon ; Electron phonon couplings ; Magic angle ; Phonon cooling ; Photo-voltage ; Time and frequencies ; Twisted bilayers ; Ultra-fast
Published in:	Science advances, Vol. 10, Issue 6 (February 2024) , art. eadj1361, ISSN 2375-2548

DOI: 10.1126/sciadv.adj1361
PMID: 38335282

9 p, 1.4 MB

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Research literature > UAB research groups literature > Research Centres and Groups (research output) > Experimental sciences > Catalan Institute of Nanoscience and Nanotechnology (ICN2)
Articles > Research articles
Articles > Published articles