Twisted square lattices: emergent symmetries and strong correlations

ORAL

Abstract

We study the electronic properties of square lattice moire homobilayers with band extrema located at the M point. At low twist angles an approximate layer-exchange symmetry emerges, that does not reduce to any crystalline symmetries of the twisted bilayer. For bands emerging from the original Brillouin zone corner, this symmetry enforces absence of nearest-neighbor hopping (t=0) on the moire lattice for the isolated flat band. Application of interlayer voltage or in-plane magnetic field allows to tune the value of t, realizing the Hubbard model with widely tunable t'/t ratio - a rich playground for high-temperature superconductivity and frustrated spin physics. Closed-form expressions for t, t' and U are obtained in the low-twist angle limit using WKB approximation and compared with exact results using Mathieu functions. We discuss the effects of band degeneracies and spin-orbit coupling, and present several candidate materials.

*This research was supported by the Center for Advancement of Topological Semimetals, an Energy Frontier Research Center funded by the U.S. Department of Energy Office of Science, Office of Basic Energy Sciences, through the Ames Laboratory under Contract No. DE-AC02-07CH11358.

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Publication: https://arxiv.org/abs/2406.02448

Presenters

  • Pavel A. Volkov

    • University of Connecticut

Authors

  • Pavel A. Volkov

    • University of Connecticut

  • Ashvin Vishwanath

    • Harvard University

  • Zhu-Xi Luo

    • Harvard University
    • Georgia Institute of Technology

  • Paul Myles Eugenio

    • University of Connecticut