Superconductivity from the condensation of topological defects in a quantum spin-Hall insulator.

Liu, Yuhai; Wang, Zhenjiu; Sato, Toshihiro; Hohenadler, Martin; Wang, Chong; Guo, Wenan; Assaad, Fakher F · Nat Commun · 2019

basic_science · Level V

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Abstract

The discovery of quantum spin-Hall (QSH) insulators has brought topology to the forefront of condensed matter physics. While a QSH state from spin-orbit coupling can be fully understood in terms of band theory, fascinating many-body effects are expected if it instead results from spontaneous symmetry breaking. Here, we introduce a model of interacting Dirac fermions where a QSH state is dynamically generated. Our tuning parameter further allows us to destabilize the QSH state in favour of a superconducting state through proliferation of charge-2e topological defects. This route to superconductivity put forward by Grover and Senthil is an instance of a deconfined quantum critical point (DQCP). Our model offers the possibility to study DQCPs without a second length scale associated with the reduced symmetry between field theory and lattice realization and, by construction, is amenable to large-scale fermion quantum Monte Carlo simulations.