Effects of intercomponent couplings on the appearance of time-reversal symmetry breaking fermion quadrupling state in two-component London models

Abstract

A detection of bosonic metallic state that breaks the Z2 time-reversal symmetry has been recently reported in Ba1−xKxFe2As2 with a doping level x ≈ 0.8. This is a metallic state of fermionic quadruplets that breaks time-reversal symmetry. As such, it has no condensate of Cooper pairs but has a long-range order between fermionic quartets. In the present manuscript, we investigate the emergence of this phase in a two-component London model via Monte Carlo simulations as a function of various intercomponent couplings.

Prediction of time-reversal-symmetry breaking fermionic quadrupling condensate in twisted bilayer graphene

“…, there arises a superconducting phase that preserves time-reversal symmetry; while for (ii) T c (Z 2 ) > T BKT , a metallic state that breaks the time-reversal symmetry forms as a result of the condensation of fermion quadruplets [11,21,24,25]. The observation of a quadruplingfermionic condensate was recently reported in the three-dimensional material Ba 1−x K x Fe 2 As 2 [24].…”