Angular momentum blockade in nanoscale high-T_c superconducting grains

TL;DR

This paper explores the phenomenon of angular momentum blockade in nanoscale d-wave superconducting grains, revealing how magnetic fields induce quantized changes in angular momentum and symmetry, with observable effects on magnetic susceptibility.

Contribution

It introduces the concept of angular momentum blockade in small superconducting grains and models its behavior using Ginzburg-Landau theory, highlighting new quantum effects.

Findings

Magnetic field causes quantized angular momentum changes in the condensate.

Deviations from d-wave symmetry to (d + id')-wave are induced by magnetic fields.

Magnetic susceptibility exhibits jumps at critical field values.

Abstract

We discuss the angular momentum blockade in small d-wave superconducting grains in an external field. We find that abrupt changes in angular momentum state of the condensate, angular momentum blockade, occur as a result of changes in the angular momentum of the condensate in an external magnetic field. The effect rep- resents a direct analogy with the Coulomb blockade. We use the Ginzburg-Landau formalism to illustrate how a magnetic field induces a deviation from the d-wave symmetry which is described by a (d + id')-order parameter. We derive the behavior of the volume magnetic susceptibility as a function of the magnetic field, and corresponding magnetization jumps at critical values of the field that should be experimentally observable in superconducting grains.