Supersolidity, the appearance of zero-viscosity flow in solids, was first indicated in helium-4 torsional oscillator (TO) experiments. In this apparatus, the irrotationality of the superfluid component causes it to decouple from the underlying normal solid, leading to a reduction in the resonant period of the TO. However, the resonant period may be altered for reasons other than supersolidity, such as the temperature dependence of the elastic modulus of solid helium. Superimposing rotation onto oscillatory measurements may distinguish between supersolidity and classical effects. We performed such simultaneous measurements of the TO and the shear modulus, and observed substantial change in the resonant period with rotational speed where the modulus remained unchanged. This contrasting behavior suggests that the decrease in the TO period is a result of supersolidity.

There are a number of distinct signatures of superfluids, one of which is the appearance of quantized vortices. There have been some attempts to understand the putative supersolid 4He in the vortex framework, but no conclusive evidence that supports the existence of the vortices has been reported. Here, we investigate the rotation velocity dependence of the torsional oscillation of solid 4He at various temperatures. The velocity sweep reveals intriguing periodic staircaselike features below about 300 mK. The staircase patterns show remarkable periodicity, and we interpret these patterns as a consequence of vortex injection. However, there are some features that cannot be accounted for with simple injection of vortices into superfluid, and further investigation is required.

We present the first results on the axion dark matter search in the axion mass range 10.13-11.17µeV at the Center for Axion and Precision Physics Research, Daejeon, Korea. The sensitivity is about 9 times larger than the Kim-Shifman-Vainstein-Zakharov coupling at 90% confidence level.

Liquid helium becomes a superfluid and flows with zero viscosity at low temperatures. Superfluidity is manifested by a failure to rotate, as its mass is decoupled from the rotation of the containing cell. Supersolid helium should show similar behaviour; apparent rotational inertia decreases when the solid helium is set into torsional oscillation below 200 mK (refs 1,2) Unlike a typical superfluid, the non-classical rotational inertia fraction (NCRIF) has been found to be partially hysteretic 8 . The low-temperature (T <∼ 20 mK) value of NCRIF for a sample was smaller when cooled down in a high-velocity field (HVF), versus that obtained at low speeds. On reducing the velocity at the lowest temperature, the NCRIF recovered the unsuppressed value. However, subsequent increases in the velocity did not result in any suppression of the NCRIF up to at least 800 µm s −1 . This hysteresis was observed only below about 40 mK. Slow warming and cooling cycles (all below 65 mK) following the above type of velocity sweeps have revealed that the NCRIF can be multivalued at the lowest temperatures 9 . The two research groups involved have described these findings in terms of the pinning of low-temperature excitations (such as dislocations and/or vortices) in solid 4 He. Here we examine the phenomena systematically by measuring the dynamic response of a torsional oscillator containing a bulk 4 He sample at a pressure of 40 bar. The sample was grown using the blocked capillary method. The torsional oscillator has an open volume of 1.92 cm 3 in a cylindrical form, with a 13 mm diameter and a height of 14.5 mm. The surface-area to volume (S/V ) ratio is 4.46 cm −1 . The empty cell has a resonant period of 1.328 ms and a mechanical quality factor of 2×10 6 at 4.2 K. Two procedures were used to reach a fixed temperature and rim velocity, both of which represent a different history. The first is a typical method from previous studies. After setting the driving voltage at 500 mK, the torsional oscillator was cooled to the base temperature of 23 mK. After equilibration at the lowest temperature, a slow warming scan was carried out. We will refer to this cooling procedure and the corresponding NCRIF as HVF cooling and HVF NCRIF, respectively. As the rim velocity v R of the torsional oscillator is temperature dependent for a constant driving voltage, we consistently denote each data set by the value of v R recorded at 23 mK.The second procedure was as follows. At 500 mK, the driving voltage was set to a low value such that v R at 23 mK is less than

Recently, exciton-polaritons in a semiconductor microcavity were found to condense into a coherent ground state much like a Bose-Einstein condensate and a superfluid. They have become a unique testbed for generating and manipulating quantum vortices in a driven-dissipative superfluid. Here, we generate exciton-polariton condensate with nonresonant Laguerre-Gaussian (LG) optical beam and verify the direct transfer of light's