U(1)_V x U(1)_A symmetry breaking in superconductivity

TL;DR

This paper proposes a novel symmetry-breaking pattern in conventional superconductivity involving U(1)_V and U(1)_A symmetries, predicting a Higgs mode alongside the Goldstone boson, unifying BCS and Ginzburg-Landau results.

Contribution

It introduces a new symmetry-breaking framework in superconductivity, highlighting the role of axial-vector symmetry and predicting a Higgs mode.

Findings

Identification of U(1)_V x U(1)_A -> U(1)_A symmetry breaking

Prediction of a Higgs mode in superconductors

Analytical results consistent with BCS and Ginzburg-Landau theories

Abstract

We argue that the general symmetry-breaking pattern in (quasi-)conventional (parity and time-reversal symmetric single-band spin-singlet) superconductivity is given by U(1)_V x U(1)_A -> U(1)_A, where V stands for vector and A stands for axial-vector, as opposed to the breaking of U(1)_V\equiv U(1)_ele/mag by itself as is commonly thought. This symmetry-breaking pattern implies that there will be a Higgs mode which, together with the Goldstone boson that is absorbed by the photon (Meissner effect), characterize the symmetry-breaking dynamics. We obtain a number of strikingly simple analytical results, which amalgamate the findings of the standard BCS and Ginzburg-Landau theories.