Superconductivity Induced by the Proximity Effect of Singlet Resonating Valence Bond Order in High-$T_c$ Superconductors

TL;DR

This paper investigates how inhomogeneous doping in high-$T_c$ cuprates can induce superconductivity at boundaries between non-superconducting regions, driven by singlet resonating valence bond order and holon condensation.

Contribution

It demonstrates that boundary regions between differently doped non-superconducting areas can host superconductivity due to resonating valence bond effects, even when the bulk remains non-superconducting.

Findings

Superconductivity can be induced at boundaries without bulk superconductivity.

The induced superconducting region can have a higher critical temperature than optimally doped samples.

Critical current density at the boundary can be comparable to that in standard superconductors.

Abstract

Effects of inhomogeneous doping on the high-$T_c$ cuprate superconductors are studied within the framework of the t-J model. Especially, the boundary between two non-superconducting regions with doping rates much higher and lower than the optimal one is examined. It is found that, although there is no superconductivity in the bulk, a superconducting region appears at the boundary because singlet resonating valence bond order and holon condensation occur simultaneously in this region. The critical temperature of the induced superconductivity can be higher than that of the optimally doped sample and the critical current density can be the same order as that in the superconducting state below the critical temperature. We also point out an experimental possibility to observe this phenomenon.