Superconductor-Insulator Transition in the TMD moir\'{e} systems and the Deconfined Quantum Critical Point

TL;DR

This paper models the superconductor-insulator transition in twisted bilayer TMD moiré systems as a deconfined quantum critical point, revealing emergent symmetries and phase transition behaviors under strain.

Contribution

It extends the DQCP framework to TMD moiré systems, identifying symmetry transformations and emergent symmetries relevant to the SIT.

Findings

SIT can be described by a DQCP with emergent SO(5) symmetry.

Strain induces either a first order transition or an easy-plane DQCP with O(4) symmetry.

The model connects lattice symmetries with quantum critical phenomena.

Abstract

We propose that the recently observed superconductor-insulator transition (SIT) in the twisted bilayer transition metal dichalcogenides moir\'{e} system at hole filling $\nu = 1$ may be described by the deconfined quantum critical point (DQCP), which was originally proposed for the transition between the N\'{e}el order and the valence bond solid (VBS) order on the square lattice. The key symmetries involved in the original DQCP include a $\mathrm{SO}(3)_s$ spin symmetry, as well as a $C_4$ lattice rotation symmetry for the VBS order that is enlarged into a $\mathrm{U}(1)_v$ symmetry near the DQCP. In the current SIT under consideration, the counterpart of the $\mathrm{SO}(3)_s$ spin symmetry is an approximate $\mathrm{SO}(3)_v$ symmetry that transforms between different crystalline orders on the triangular lattice; and the role of the $\mathrm{U}(1)_v$ symmetry is replaced by the ordinary charge-$\mathrm{U}(1)_e$ symmetry. And at the DQCP the $\mathrm{SO}(3)_v \times \mathrm{U}(1)_e$ may enlarge into an emergent $\mathrm{SO}(5)$ symmetry. Under strain, the SIT is driven into either a prominent first order transition, or an "easy-plane" DQCP, which is expected to have an emergent $\mathrm{O}(4)$ symmetry.