Searching for thermal signatures of persistent currents in normal metal rings

TL;DR

This study uses nanocalorimetry to detect magnetic-field-dependent heat capacity oscillations in normal metal rings, revealing signatures of persistent currents consistent with theory in period but larger amplitude.

Contribution

It introduces a calorimetric method to observe persistent currents in normal metal rings and reports unexpected large amplitude oscillations.

Findings

Periodic oscillations in heat capacity with magnetic flux are observed.

Oscillation period matches theoretical predictions.

Amplitude of oscillations exceeds theoretical expectations by two orders of magnitude.

Abstract

We introduce a calorimetric approach to probe persistent currents in normal metal rings. The heat capacity of a large ensemble of silver rings is measured by nanocalorimetry under a varying magnetic field at different temperatures (60 mK, 100 mK and 150 mK). Periodic oscillations versus magnetic field are detected in the phase signal of the temperature oscillations, though not in the amplitude (both of them directly linked to the heat capacity). The period of these oscillations ($\Phi_0/2$, with $\Phi_0 = h/e$ the magnetic flux quantum) and their evolution with temperature are in agreement with theoretical predictions. In contrast, the amplitude of the corresponding heat capacity oscillations (several $k_{\mathrm{B}}$) is two orders of magnitude larger than predicted by theory.