Superconducting Decoherence and Thermal Quenching of the Josephson Diode Effect in Low-Dimensional Josephson Systems

TL;DR

This paper reveals that in low-dimensional Josephson systems, superconducting phase decoherence occurs through multiple distinct thermal crossovers, affecting the Josephson diode effect and coherence at different temperatures, with implications for layered superconductors and qubit platforms.

Contribution

It introduces a fully self-consistent microscopic framework showing that superconducting decoherence and diode nonreciprocity are separated into distinct energy scales, contrary to conventional single-scale models.

Findings

Diode effect disappears at temperature T_eta

Josephson coherence is lost at T_c

Superconducting gap collapses at T_s

Abstract

Motivated by recent studies on superconducting (SC) diode nonreciprocity, we uncover a generic smooth SC-phase decoherence mechanism in low-dimensional Josephson structures. Contrary to the conventional single-energy-scale paradigm where Josephson coherence and diode nonreciprocity vanish simultaneously only at the SC gap-closing temperature, we demonstrate, within a fully self-consistent microscopic framework beyond mean-field theory, that SC phase fluctuations generically split these phenomena into distinct energy scales. As a result, rather than a single SC-normal transition, the system exhibits a sequence of distinct thermal crossovers upon heating: the diode effect disappears first at $T_{\eta}$, Josephson coherence is subsequently lost at $T_c$, and the SC gap collapses only at a higher temperature $T_s$. Using a bilayer SC system as a concrete example, we show that the separation between these temperature scales is not solely dictated by Josephson coupling, but is instead strongly and counterintuitively shaped by the in-plane disorder and carrier density. These findings reveal that smooth SC phase decoherence introduces a distinct and more fragile energy scale, with potential implications for layered superconductors such as cuprates and recently discovered nickelates, as well as for SC qubit platforms.