Probable Observation of Quantized Vortex Lines Through Solid He Under DC Rotation

We report how one can detect quantized vortices in superfluids contained in cylindrical vessels in well-designed torsional oscillator (TO) experiments under DC rotation. We show the case of an artificial 3D superfluid (Fukuda et al. in Phys. Rev. B 71:212502, 2005) which is made of Kosterlits-Thouless 2D He film condensed on a porous glass substrate with a 3D connected surface of well-controlled pore size. We understand the TO experimental results with an extra energy dissipation peak under DC rotation by considering the circular quantized superflow around each of the vortex lines and interaction with thermally excited 2D vortices as discussed in Fukuda et al. (Phys. Rev. B 71:212502, 2005) and in Nemirovskii and Sonin (Phys. Rev. B 76: 224507, 2007). We discuss here the case of hcp solid (4)He (see for ex. Balibar and Caupin in J. Phys., Condens. Matter 20:173201-1-19, 2008) and show the evidence of observation of the vortex lines penetration below a supersolid transition temperature (Kubota et al. in J. Low Temp. Phys. 158:572, 2010), T(c), where macroscopic phase coherence is realized. It is found at exactly the same temperature T(c), below which the hysteresis occurrs (Shimizu et ail. in arXiv:0903.1326, 2009). For hcp solid (4)He we have reported the vortex fluid (VF) state onset temperature (Penzev et al. in Phys. Rev. Lett. 101:065301, 2008) T(o) = similar to 500 mK, by detailed drive velocity, V(ac) dependence study using TO technique. The TO response of the hcp (4)He is characterized by the energy dissipation peaked at T(p) near 100 mK similar to the behavior in a KT transition. The real supersolid (SS) state occurs at T(c) below T(p) and much lower than T (o) . Our observation of the evidence of vortex lines penetration just below T (c) together with the VF state properties gives support for the idea that hcp (4)He shares some features with the new type of superconductors, where the vortex state, involving the VF as well as various vortex solid states, has been commonly discussed (Fisher et al. in Phys. Rev. B 43(1):130, 1991; Leggett in Quantum Liquids, Oxford University Press, London, 2006).