Higgs-Leggett mechanism for the elusive $${\phi }_{0}/3={hc}/6e$$ ϕ 0 / 3 = h c / 6 e oscillation in Little-Parks setup of Kagome superconductor CsV3Sb5

Abstract

Abstract A recent Little-Parks experiment in Kagome-structured superconductor CsV3Sb5 demonstrated resistance oscillations with period $${\phi }_{0}/3={hc}/6e$$ ϕ 0 / 3 = h c / 6 e . Here, we perform analysis based on a theory involving three $$2{{{{{\rm{e}}}}}}$$ 2 e superconductivity (SC) order parameters associated with the three reciprocal lattice vectors which connect M points of the hexagonal Brillouin zone. In a ring geometry we find that, as a series of intermediate states, phase of one SC order parameter winds 2π more or less than the other two ones around the ring, which yields local free-energy minima at integer multiples of $${\phi }_{0}/3$$ ϕ 0 / 3 . It is unveiled that the ground-state degeneracy associated with a Z2 chirality is crucial, and the Higgs-Leggett mechanism stabilizes domain walls (DWs) between chiral domains. At low temperatures DWs are expelled from the system resulting in free-energy minima only at integer multiples of $${\phi }_{0}$$ ϕ 0 . Our theory explains successfully the fractional quantization of magnetic flux $${\phi }_{0}/3$$ ϕ 0 / 3 observed in experiments, which opens a door for approaching rich physics of Kagome superconductors.