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Observation of non-classical rotational inertia in bulk solid 4He

Motoshi Kondo·Shunichi Takada·Yoshiyuki Shibayama·Keiya Shirahama
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Abstract

In recent torsional oscillator experiments by Kim and Chan (KC), a decrease of rotational inertia has been observed in solid 4He in porous materials and in a bulk annular channel. This observation strongly suggests the existence of "non-classical rotational inertia" (NCRI), i.e. superflow, in solid 4He. In order to study such a possible "supersolid" phase, we perform torsional oscillator experiments for cylindrical solid 4He samples. We have observed decreases of rotational inertia below 200 mK for two solid samples (pressures P = 4.1 and 3.0 MPa). The observed NCRI fraction at 70 mK is 0.14 %, which is about 1/3 of the fraction observed in the annulus by KC. Our observation is the first experimental confirmation of the possible supersolid finding by KC.

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Motoshi Kondo, Shunichi Takada, Yoshiyuki Shibayama, Keiya Shirahama. 2006-07-03. Observation of non-classical rotational inertia in bulk solid 4He. https://doi.org/10.1007/s10909-007-9471-1

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