Bulletin of the American Physical Society
APS March Meeting 2024
Monday–Friday, March 4–8, 2024; Minneapolis & Virtual
Session W09: Superconductivity in Magic Angle Moiré Graphene Stacks
3:00 PM–6:00 PM,
Thursday, March 7, 2024
Room: L100J
Sponsoring
Unit:
DCMP
Chair: Chunli Huang, University of Kentucky
Abstract: W09.00014 : Signatures of heavy electron bands in the thermoelectric response of MATBG pn-junctions
5:36 PM–5:48 PM
Presenter:
Rafael Luque Merino
(Ludwig Maximilian Universiteit (LMU, Munich))
Authors:
Rafael Luque Merino
(Ludwig Maximilian Universiteit (LMU, Munich))
Paul Seifert
(Universitat der Bundeswehr)
Dumitru Calugaru
(Princeton University)
Andres Díez-Carlón
(LMU)
Jaime Diez Merida
(LMU)
Haoyu Hu
(Donostia International Physics Center)
Andrei B Bernevig
(Princeton University)
Dmitri K Efetov
(LMU)
Dmitri K Efetov
(LMU)
These observations have motivated the development of multi-orbital models, such as the Topological Heavy Fermion (THF) model, to describe the MATBG flat bands and provide an analytical treatment of electron correlations in the flat bands. Still, the consequences of the coexistence of light (itinerant) and heavy (localized) electron bands in the transport of the MATBG flat bands have not been described. In this work, we present measurements of the thermoelectric (TE) response of the MATBG flat bands and model the low-temperature thermoelectric response using the THF model. We illuminate high-quality, gate-defined MATBG pn-junctions with a focused laser source (1550 nm) and read out the thermoelectric response through the Seebeck-driven photo-thermoelectric (PTE) effect in the presence of non-uniform filling factor along the junction. We establish the PTE-mechanism as the dominant photovoltage-generating mechanism in MATBG for above-gap excitation. Then, we reveal a previously unreported regime of the TE response of the MATBG flat bands, where the response remains electron-like through the conduction flat bands. We find that this response is consistent with the presence of low-energy heavy fermion bands which do not contribute to transport, causing an asymmetry of the PTE signal. We illustrate the role of carrier lifetime, set by the interaction strength, in the transport of MATBG.
Lastly, we study the PTE response at high temperatures, beyond the ordering temperatures for correlated ground states and find evidence for strong electronic interactions. This observation can be accounted for using the Kondo lattice model of MATBG, where the conduction electrons scatter off the moire lattice of interacting, localized electrons.
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700