Enhanced chiral edge currents and orbital magnetic moment in chiral d-wave superconductors from mesoscopic finite-size effects

Abstract

Chiral superconductors spontaneously break time-reversal symmetry and host topologically protected edge modes, supposedly generating chiral edge currents which are typically taken as a characteristic fingerprint of chiral superconductivity. However, recent studies have shown that the total edge current in two dimensions (2D) often vanishes for all chiral superconductors except for chiral p-wave, especially at low temperatures, thus severely impeding potential experimental verification and characterization of these superconductors. In this work, we use the quasiclassical theory of superconductivity to study mesoscopic disk-schaped chiral d-wave superconductors. We find that mesoscopic finite-size effects cause a dramatic enhancement of the total charge current and orbital magnetic moment (OMM), even at low temperatures. We study how these quantities scale with temperature, spontaneous Meissner screening, and system radius R∈[5,200]ξ0 with superconducting coherence length ξ0. We find a general 1/R scaling in the total charge current and OMM for sufficiently large systems, but this breaks down in small systems, instead producing a local maximum at R≈10–20ξ0 due to mesoscopic finite-size effects. These effects also cause a spontaneous charge-current reversal opposite to the chirality below R<10ξ0. Our work highlights mesoscopic systems as a route to experimentally verify chiral d-wave superconductivity, measurable with magnetometry.

Source-reported materials — not catalogue approval

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