Superconductor-Insulator Transition in the TMD moir\'e systems and the Deconfined Quantum Critical Point
Abstract
We propose that the recently observed superconductor-insulator transition (SIT) in the twisted bilayer transition metal dichalcogenides moir\'e system at hole filling = 1 may be described by the deconfined quantum critical point (DQCP), which was originally proposed for the transition between the N\'eel order and the valence bond solid (VBS) order on the square lattice. The key symmetries involved in the original DQCP include a SO(3)s spin symmetry, as well as a C4 lattice rotation symmetry for the VBS order that is enlarged into a U(1)v symmetry near the DQCP. In the current SIT under consideration, the counterpart of the SO(3)s spin symmetry is an approximate SO(3)v symmetry that transforms between different crystalline orders on the triangular lattice; and the role of the U(1)v symmetry is replaced by the ordinary charge-U(1)e symmetry. And at the DQCP the SO(3)v × U(1)e may enlarge into an emergent 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 O(4) symmetry.
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