$\phi_0$-junction and Josephson diode effect in high-temperature superconductor

TL;DR

This paper proposes a high-temperature superconductor Josephson junction model exhibiting the Josephson diode effect, highlighting the role of symmetry breaking and suggesting experimental detection methods for unconventional pairing symmetries.

Contribution

It introduces a novel mechanism for the Josephson diode effect in high-temperature superconductors based on symmetry considerations and proposes experimental signatures for detecting unconventional pairing.

Findings

JDE depends on C4 rotational symmetry.

Breaking C4 symmetry controls diode efficiency.

Proposed observation via asymmetric Shapiro steps.

Abstract

Motivated by recent progress in both the Josephson diode effect (JDE) and the high-temperature Josephson junction, we propose to realize the JDE in an s-wave/d-wave/s-wave (s-d-s) superconductor junction and investigate the high-temperature superconducting order parameters. The interlayer coupling between s-wave and d-wave superconductors can induce an effective $d+is$ superconducting state, spontaneously breaking time-reversal symmetry. The asymmetric s-d interlayer couplings break the inversion symmetry. Remarkably, the breaking of these two symmetries leads to a $\phi_0$-junction but does not generate JDE. We find that the emergence of the JDE in this junction depends on the $C_4$ rotational symmetry of the system. Although breaking $C_4$ rotational symmetry does not affect time-reversal and inversion symmetries, it can control the magnitude and polarity of diode efficiency. Furthermore, we propose observing C$_{4}$ symmetry breaking controlled JDE through asymmetric Shapiro steps. Our work suggests a JDE mechanism that relies on high-temperature d-wave pairing, which could inversely contribute to a potential experimental method for detecting the unconventional pairing symmetry in superconductors.