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Different mechanisms driving a linear temperature dependence of the resistivity at van Hove singularities (VHSs) or metal-insulator transitions when doping a Mott insulator are being debated intensively with competing theoretical proposals. We experimentally investigate this using the exceptional tunability of twisted bilayer (TB-) WSe2 by tracking the parameter regions where linear-in-T resistivity is found in dependency of displacement fields, filling, and magnetic fields. We find that even when the VHSs are tuned rather far away from the half-filling point and the Mott insulating transition is absent, the T-linear resistivity persists at the VHSs. When doping away from the VHSs, the T-linear behavior quickly transitions into a Fermi liquid behavior with a T2 relation. No apparent dependency of the linear-in-T resistivity, besides a rather strong change of prefactor, is found when applying displacement fields as long as the filling is tuned to the VHSs, including D~ 0.28 V/nm where a higher order VHS is expected. Intriguingly, such non-Fermi liquid linear-in-T resistivity persists even when magnetic fields break the spin-degeneracy of the VHSs at which point two linear in T regions emerge, for each of the split VHSs separately. This points to a mechanism of enhanced scattering at generic VHSs rather than only at high-order VHSs or by a quantum critical point during a Mott transition. Our findings provide insights into the many-body consequences arising out of VHSs, especially the non-Fermi liquid behavior found in moiré materials.

Rights:

• Creative Commons BY Attribution 4.0 International
  

Keyword: Resistivity, van Hove singularities, twisted bilayer WSe2

Date published: 2024-04-16

Publisher: Proceedings of the National Academy of Sciences

Journal:

• Proceedings of the National Academy of Sciences (ISSN: 10916490) vol. 121 issue. 16 e2321665121

Funding:

• National Science Foundation of Jiangsu Province BK20220066
• National Key Research and Development Program of China 2022YFA1403501
• Guandong Basic and Applied Basic Research Foundation 2022B1515120020
• Hefei National Research Center for Physical Sciences at the Microscale KF2021003
• Max Planck Partner group programme -
• Max Planck-New York City Center for Non-Equilibrium Quantum Phenomena -
• University of Wisconsin-Madison, Office of the Vice Chancellor for Research and Graduate Education -
• JSPS KAKENHI 21H05233 and 23H02052
• National Natural Science Foundation of china 12074173
• Deutsche Forschungsgemeinschaft EXC 2004/1 - 390534769

Manuscript type: Publisher's version (Version of record)

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First published URL: https://doi.org/10.1073/pnas.2321665121

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Updated at: 2025-02-23 22:46:54 +0900

Published on MDR: 2025-02-23 22:46:54 +0900