Absence of low temperature anomaly in the Debye-Waller factor of solid He-4

TL;DR

This study measures atomic displacements in solid He-4 and finds no low-temperature anomaly near the supersolid transition, indicating stable atomic behavior across the temperature range.

Contribution

It provides the first precise measurements of mean square displacements in solid He-4, showing no anomaly near the supersolid transition temperature.

Findings

Mean square displacement is temperature independent from 1 K to 140 mK.

Displacements differ between in-plane and out-of-plane motions.

No evidence of a low-temperature anomaly near the supersolid transition.

Abstract

The mean square atomic displacement in hcp-phase solid He-4 has been measured in crystals with a molar volume of 21.3 cm^3. It is temperature independent from 1 K to 140 mK, with no evidence for an anomaly in the vicinity of the proposed supersolid transition. The mean square displacement is different for in-plane motions (0.122 +/- 0.001 A^(2)) and out-of-plane motions (0.150 +/- 0.001 A ^(2)).