Evidence for Supersolidity in Bulk Solid $^4$He

• DOI: 10.48550/arxiv.1407.1515
• Publication Date: 2014-01-01
• Authors: Mi, Xiao; Eyal, Anna; Talanov, Artem V.; Reppy, John D.
• Keywords: Condensed Matter - Other Condensed Matter; 0103 physical sciences; FOS: Physical sciences; 01 natural sciences; Other Condensed Matter (cond-mat.other)

We report low temperature measurements of bulk solid $^4$He in a two-frequency compound torsional oscillator with both annular and open cylinder sample geometries. The oscillators were designed to suppress period shifts arising from all known elastic effects of solid $^4$He. At temperatures below 0.25 K, period shift signals similar to those reported by Kim and Chan [Science {\bf 305}, 1941 (2004)] were observed, albeit two orders smaller in magnitude. A sizable fraction of the observed signals are frequency-independent and consistent with the mass-decoupling expected for supersolid $^4$He. This result is in stark contrast with recent works on Vycor-solid-$^4$He system and suggests that a small supersolid fraction on the order of $1 \times 10^{-4}$ may indeed exist in bulk solid $^4$He.<br/>5 pages, 5 figures, Supplement 4 pages, 2 figures<br/>