Non-Boltzmann thermoelectric transport in minimally twisted bilayer graphene

Ghawri, B and Mahapatra, PS and Garg, M and Mandal, S and Jayaraman, A and Watanabe, K and Taniguchi, T and Jain, M and Chandni, U and Ghosh, A (2024) Non-Boltzmann thermoelectric transport in minimally twisted bilayer graphene. In: Physical Review B, 109 (4).

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Abstract

The electronic bands formed in moiré systems with twisted bilayer graphene (tBLG) have emerged as a tunable platform for studying many novel concepts of condensed matter physics due to new interaction and topological effects. In particular, the multitude of closely packed flat bands and a sequence of van Hove singularities (vHSs) in minimally tBLG can not only lead to nontrivial topological transport but also the breakdown of conventional Boltzmann transport formalism due to the competition between the scales of energy variation within the system and that of the external parameters such as temperature or electric field. Here, we demonstrate the violation of the semiclassical Mott relation in small-angle tBLG (θ�0.45°) even at room temperature, which we associate to a narrow diverging density of states. We also show the emergence of nonlinear effects in thermovoltage by exploiting vertical thermoelectric transport in an atomically thin tBLG device. Our results not only point towards the fundamental limitations of the applicability of the semiclassical Boltzmann approach in small-angle tBLG but also outline an experimental approach that can lead to the discovery of different broken-symmetry states. © 2024 American Physical Society.

Item Type:	Journal Article
Publication:	Physical Review B
Publisher:	American Physical Society
Additional Information:	The copyright for this article belongs to American Physical Society.
Keywords:	Electric fields; Topology, Bilayer Graphene; Boltzmann; Condensed-matter physics; Electronic band; Interaction effect; Novel concept; Thermoelectric transport; Topological effects; Tunables; Twisted bilayers, Graphene
Department/Centre:	Division of Interdisciplinary Sciences > Centre for Nano Science and Engineering Division of Physical & Mathematical Sciences > Instrumentation Appiled Physics Division of Physical & Mathematical Sciences > Physics
Date Deposited:	03 Mar 2024 08:55
Last Modified:	03 Mar 2024 08:55
URI:	https://eprints.iisc.ac.in/id/eprint/84169

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