Dissipationless counterflow currents above T_c in bilayer superconductors

TL;DR

This paper demonstrates that in bilayer superconductors, counterflow currents can remain dissipationless above the critical temperature due to phase fluctuations and vortex dynamics, offering insights into the pseudogap phase.

Contribution

The study introduces a semiclassical $U(1)$ lattice gauge theory showing dissipationless counterflow currents above $T_c$, highlighting a novel mechanism for pseudogap behavior in bilayer cuprates.

Findings

Counterflow currents remain dissipationless above T_c.

Vortex proliferation causes resistive behavior in homogeneous currents.

Local superconducting coherence inhibits vortex motion in counterflow channels.

Abstract

We report the existence of dissipationless currents in bilayer superconductors above the critical temperature $T_c$, assuming that the superconducting phase transition is dominated by phase fluctuations. Using a semiclassical $U(1)$ lattice gauge theory, we show that thermal fluctuations cause a transition from the superconducting state at low temperature to a resistive state above $T_c$, accompanied by the proliferation of unbound vortices. Remarkably, while the proliferation of vortex excitations causes dissipation of homogeneous in-plane currents, we find that counterflow currents, flowing in opposite direction within a bilayer, remain dissipationless. The presence of a dissipationless current channel above $T_c$ is attributed to the inhibition of vortex motion by local superconducting coherence within a single bilayer, in the presence of counterflow currents. Our theory presents a possible scenario for the pseudogap phase in bilayer cuprates.