Non-classical response from quench-cooled solid helium confined in porous gold

Abstract

We have investigated the non-classical response of solid 4He confined in\nporous gold set to torsional oscillation. When solid helium is grown rapidly,\nnearly 7% of the solid helium appears to be decoupled from the oscillation\nbelow about 200 mK. Dissipation appears at temperatures where the decoupling\nshows maximum variation. In contrast, the decoupling is substantially reduced\nin slowly grown solid helium. The dynamic response of solid helium was also\nstudied by imposing a sudden increase in the amplitude of oscillation. Extended\nrelaxation in the resonant period shift, suggesting the emergence of the\npinning of low energy excitations, was observed below the onset temperature of\nthe non-classical response. The motion of a dislocation or a glassy solid is\nrestricted in the entangled narrow pores and is not likely responsible for the\nperiod shift and long relaxation.\n