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Re-entrant superconductivity in twisted trilayer graphene

Senthil Todadri, MIT

Hosted by Young Lee

Event Details:

Thursday, June 3, 2021
3:15pm - 4:00pm PDT

Abstract

A series of recent experiments has demonstrated robust superconductivity in magic-angle twisted trilayer graphene (TTG). In particular, a recent work by Cao et al. (arXiv:2103.12083) studies the behavior of the superconductor in an in-plane magnetic field and out-of-plane displacement field, finding that the superconductor is unlikely to be spin-singlet. This work also finds that at high magnetic fields and a smaller range of dopings and displacement fields, it undergoes a transition to a distinct field-induced superconducting state. Inspired by this, we* develop an understanding of the role that that an in-plane field plays in TTG, and use this understanding to argue that the transition may be associated with a quantum Lifshitz phase transition, with the high-field phase possessing finite-momentum pairing. Along the way we will also develop an understanding of the normal state, and will show how in TTG (and likely also in twisted bilayer graphene) the resistive state at filling -2 may involve a time reversal protected topological insulator obtained by spontaneous spin symmetry breaking.

*Work done with Ethan Lake (Lake, TS, arXiv:2104.13920).

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