Broken Time Reversal Symmetry and Superconducting States in the Cuprates

TL;DR

This paper explores how broken time reversal symmetry in cuprates leads to a novel mixed pairing superconducting state, impacting the order parameter and potentially observable in Josephson experiments.

Contribution

It introduces a new d+ip mixed singlet-triplet pairing state arising from broken time reversal symmetry in cuprates.

Findings

Broken time reversal symmetry induces a d+ip superconducting phase.

The d+ip state results in a helical superconducting phase.

Implications for Josephson experiments are discussed.

Abstract

Recently, Kaminski et al. have reported that time reversal symmetry is broken in the pseudogap phase in the high temperature superconducting material Bi_2Sr_2CaCu_2O_{2+\delta} (Bi-2212). Here we examine the role of translationally invariant broken time reversal states on d_{x^2-y^2} superconductors. In particular, we determine the change in the superconducting order parameter structure. We find that the broken time reversal pseudogap state that is consistent with the experiment of Kaminski et al., gives rise to a novel mixed singlet-triplet pairing d+ip phase. This d+ip state is shown to give rise to a helical superconducting phase. Consequences of this d+ip state on Josephson experiments are discussed.