Thermopower Oscillation Symmetries in a Double-Loop Andreev Interferrometer

TL;DR

This paper investigates how the thermopower oscillation symmetries in a double-loop Andreev interferometer depend on sample geometry, providing insights into the phase-coherent thermal transport in hybrid superconducting-normal metal devices.

Contribution

It presents experimental measurements of thermopower oscillations in a double-loop interferometer, revealing geometry-dependent symmetry behaviors not fully explained by existing theory.

Findings

Thermopower oscillations can be symmetric or antisymmetric depending on sample geometry.

The amplitude and symmetry of oscillations are controllable via Josephson currents.

Results suggest geometry plays a crucial role in phase-coherent thermoelectric effects.

Abstract

Andreev interferometers, normal metal wires coupled to superconducting loops, display phase coherent changes as the magnetic flux through the superconducting loops is altered. Properties such as the electronic and thermal conductance of these devices have been shown to oscillate symmetrically about zero with a period equal to one superconducting flux quantum, $\Phi_o = h/2e$. However, the thermopower of these devices can oscillate symmetrically or antisymmetrically depending on the geometry of the sample, a phenomenon not well understood theoretically. Here we report on thermopower measurements of a double-loop Andreev interferometer where two Josephson currents in the normal metal wire may be controlled independently. The amplitude and symmetries of the observed thermopower oscillations may help to illuminate the unexplained dependence of oscillation symmetry on sample geometry.