Quantized vortex state in hcp solid 4He

TL;DR

This paper discusses the quantized vortex state in hcp solid helium-4, exploring its transition to a supersolid phase, and compares it with vortex phenomena in high-temperature superconductors, highlighting unique features of quantum solid vortices.

Contribution

It provides a detailed analysis of the vortex fluid state in hcp 4He and its relation to supersolidity, offering new insights into low-dimensional vortex excitations in quantum solids.

Findings

Evidence for vortex fluid state in hcp 4He

Transition mechanisms to supersolid phase

High onset temperature explained by low-dimensional vortices

Abstract

The quantized vortex state appearing in the recently discovered new states in hcp 4He since their discovery is discussed. Special attention is given to evidence for the vortex state as the vortex fluid (VF) state and its transition into the supersolid (SS) state. Its features are described. The historical expla- nations for the SS state in quantum solids such as solid 4He were based on the idea of Bose Einstein Condensation (BEC) of the imperfections such as va- cancies, interstitials and other possible excitations in the quantum solids which are expected because of the large zero-point motions. The SS state was proposed as a new state of matter in which real space ordering of the lattice structure of the solid coexists with the momentum space ordering of superfluidity. A new type of superconductors, since the discovery of the cuprate high Tc superconductors, HTSCs, has been shown to share a feature with the vortex state, involving the VF and vortex solid states. The high Tcs of these materials are being discussed in connection to the large fluctuations associated with some other phase transitions like the antiferromagnetic transition in addition to that of the low dimensionality. The supersolidity in the hcp solid 4He, in contrast to the new superconductors which have multiple degrees of freedom of the Cooper pairs with spin as well as angular momentum freedom, has a unique feature of possessing possibly only the momentum fluctuations and vortex ring excitations associated with the possible low dimensional fluctuations of the subsystem(s). The high onset temperature of the VF state can be understood by considering thermally excited low D quantized vortices and it may be necessary to seek low dimensional sub-systems in hcp He which are hosts for vortices.