Calorimetric measurement of nuclear spin-lattice relaxation rate in metals

TL;DR

This study introduces a non-resonant calorimetric method to measure nuclear spin-lattice relaxation rates in metals, providing insights into electronic correlations and quasiparticle dynamics without traditional NMR techniques.

Contribution

It demonstrates a novel non-resonant calorimetric approach to determine nuclear spin-lattice relaxation times in metals across a wide temperature and magnetic field range.

Findings

Successful measurement of relaxation times in indium from 0.3 K to 7 K

Effective detection of relaxation effects via frequency dispersion in calorimeter response

Applicable in high magnetic fields up to 35 T

Abstract

The quasiparticle density of states in correlated and quantum-critical metals directly probes the effect of electronic correlations on the Fermi surface. Measurements of the nuclear spin-lattice relaxation rate provide one such experimental probe of quasiparticle mass through the electronic density of states. By far the most common way of accessing the spin-lattice relaxation rate is via nuclear magnetic resonance and nuclear quadrupole resonance experiments, which require resonant excitation of nuclear spin transitions. Here we report non-resonant access to spin-lattice relaxation dynamics in AC-calorimetric measurements. The nuclear spin-lattice relaxation rate is inferred in our measurements from its effect on the frequency dispersion of the thermal response of the calorimeter-sample assembly. We use fast, lithographically-defined nanocalorimeters to access the nuclear spin-lattice relaxation times in metallic indium from 0.3~K to 7~K and in magnetic fields up to 35~T.