Simultaneous Measurement of Torsional Oscillator and NMR of Very Dilute 3He in Solid 4He

TL;DR

This study simultaneously measures NMR and torsional oscillator responses of dilute 3He in solid 4He, revealing three distinct 3He states and suggesting nonuniform crystal regions influence supersolid behavior.

Contribution

It identifies three different 3He states in solid 4He and links nonuniform crystal regions with supersolid phenomena, providing new insights into impurity effects.

Findings

Three 3He states identified: isolated atoms, clusters below phase separation, and clusters in nonuniform regions.

Presence of 3He in nonuniform regions affects supersolid response.

Even ppm levels of 3He influence the supersolid behavior in torsional oscillator experiments.

Abstract

We have investigated the NMR properties of dilute 3He impurities in solid 4He contained in a torsional oscillator (TO) by the simultaneous measurement of the NMR and the torsional oscillator response of the so-called supersolid 4He. From measurements on samples with one hundred to a few hundred ppm of 3He, we have found three different states of 3He. The first is the homogeneously distributed isolated 3He atom in a solid matrix of 4He. The second is the 3He cluster in a homogeneous 4He matrix, which appears below the phase separation temperature of a solid mixture. The third is the 3He cluster in some nonuniform part of a 4He crystal. We find that 3He atoms contained in the third component remain in a nearby location even above the phase separation temperature. Based on the fact that even a ppm of 3He affects the supersolid response in a TO below and above the phase separation temperature, we propose that the nonuniform part of a crystal that holds the third type of 3He and thus has a higher local concentration of 3He plays an important role in the supersolid phenomenon in a TO.