[qmeso-seminar] семинар 24 октября

[Quantum Mesoscopics Dept.]

СЕМИНАР СЕКТОРА КВАНТОВОЙ МЕЗОСКОПИКИ

пятница 24 октября, 15:00, ИТФ



Максим Парфёнов

Topologically enabled superconductivity: possible implications for rhombohedral graphene



Реферативный доклад по работе:
https://arxiv.org/pdf/2504.13166

We present a topological mechanism for superconductivity emerging from Chern-2 insulators.
While, naively, time-reversal symmetry breaking is expected to prevent superconductivity, it turns
out that the opposite is the case: An explicit model calculation for a generalized attractive-U
Haldane-Hubbard model demonstrates that superconductivity is only stabilized near the quantum
anomalous Hall state, but not near a trivial, time-reversal symmetric band insulator. As standard
Bardeen-Cooper-Schrieffer-like mean-field theory fails to capture any superconducting state, we
explain this using an effective fractionalized field theory involving fermionic chargeons, bosonic
colorons and an emergent U(1) gauge field. When the chargeons form a gapped topological band
structure, the proliferation of single monopoles of this gauge field is forbidden. However, long-ranged
monopole-antimonopole correlations emerge, and we argue that those correspond to superconducting
order. Using random phase approximation on top of extensive slave-rotor mean-field calculations
we characterize coherence length and stiffness of the superconductor. Thereby, we deduce the
phase diagram in parameter space and furthermore discuss the effect of doping, temperature and an
external magnetic field. We complement the fractionalized theory with calculations using an effective
spin model and Gutzwiller projected wavefunctions. While mostly based on a simple toy model, we
argue that our findings contribute to a better understanding of superconductivity emerging out of
spin- and valley polarized rhombohedral graphene multilayers in a parameter regime with nearby
quantum anomalous Hall insulators.



[Трансляция: https://zoom.us/j/96948399564?pwd=RXlKbW96Qm1tZEV6SHB0Q2JYeTdrdz09]

подробнее: http://qmeso.itp.ac.ru/seminars.php?abstract=true