Tunable spin and valley excitations of correlated insulators in Γ-valley moiré bands

Benjamin A Foutty; Jiachen Yu; Trithep Devakul; Carlos R Kometter; Yang Zhang; Kenji Watanabe; Takashi Taniguchi; Liang Fu; Benjamin E Feldman

doi:10.1038/s41563-023-01534-z

Tunable spin and valley excitations of correlated insulators in Γ-valley moiré bands

Nat Mater. 2023 Jun;22(6):731-736. doi: 10.1038/s41563-023-01534-z. Epub 2023 Apr 17.

Authors

Benjamin A Foutty^#^{1

2}, Jiachen Yu^#^{1

3}, Trithep Devakul^#⁴, Carlos R Kometter^{1

2}, Yang Zhang^{4

5

6}, Kenji Watanabe⁷, Takashi Taniguchi⁸, Liang Fu⁴, Benjamin E Feldman^{9

10

11}

Affiliations

¹ Geballe Laboratory for Advanced Materials, Stanford, CA, USA.
² Department of Physics, Stanford University, Stanford, CA, USA.
³ Department of Applied Physics, Stanford University, Stanford, CA, USA.
⁴ Department of Physics, Massachusetts Institute of Technology, Cambridge, MA, USA.
⁵ Department of Physics and Astronomy, University of Tennessee, Knoxville, TN, USA.
⁶ Min H. Kao Department of Electrical Engineering and Computer Science, University of Tennessee, Knoxville, TN, USA.
⁷ Research Center for Functional Materials, National Institute for Material Science, Tsukuba, Japan.
⁸ International Center for Materials Nanoarchitectonics, National Institute for Material Science, Tsukuba, Japan.
⁹ Geballe Laboratory for Advanced Materials, Stanford, CA, USA. bef@stanford.edu.
¹⁰ Department of Physics, Stanford University, Stanford, CA, USA. bef@stanford.edu.
¹¹ Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, CA, USA. bef@stanford.edu.

^# Contributed equally.

PMID: 37069292
DOI: 10.1038/s41563-023-01534-z

Abstract

Moiré superlattices formed from transition metal dichalcogenides support a variety of quantum electronic phases that are highly tunable using applied electromagnetic fields. While the valley degree of freedom affects optoelectronic properties in the constituent transition metal dichalcogenides, it has yet to be fully explored in moiré systems. Here we establish twisted double-bilayer WSe₂ as an experimental platform to study electronic correlations within Γ-valley moiré bands. Through local and global electronic compressibility measurements, we identify charge-ordered phases at multiple integer and fractional moiré fillings. By measuring the magnetic field dependence of their energy gaps and the chemical potential upon doping, we reveal spin-polarized ground states with spin-polaron quasiparticle excitations. In addition, an applied displacement field induces a metal-insulator transition driven by tuning between Γ- and K-valley moiré bands. Our results demonstrate control over the spin and valley character of the correlated ground and excited states in this system.

Grants and funding

NSF-DMR-2103910/National Science Foundation (NSF)