We report measurements of elastic moduli of hcp solid 4He down to 15 mK when the samples are rotated unidirectionally. Recent investigations have revealed that the elastic behavior of solid 4He is dominated by gliding of dislocations and pinning of them by 3He impurities, which move in the solid like Bloch waves (impuritons). Motivated by the recent controversy of torsional oscillator studies, we have preformed direct measurements of shear and Young’s moduli of annular solid 4He using pairs of quarter-circle shape piezoelectric transducers (PZTs) while the whole apparatus is rotated with angular velocity Ω up to 4 rad/s. We have found that shear modulus µ is suppressed by rotation below 80 mK, when shear strain applied by PZT exceeds a critical value, above which µ decreases because the shear strain unbinds dislocations from 3He impurities. The rotation - induced decrement of µ at Ω = 4 rad/s is about 14.7(12.3) % of the total change of temperature dependent µ for solid samples of pressure 3.6(5.4) MPa. The decrements indicate that the probability of pinning of 3He on dislocation segment, G, decreases by several orders of magnitude. We propose that the motion of 3He impuritons under rotation becomes strongly anisotropic by the Coriolis force, resulting a decrease in G for dislocation lines aligning parallel to the rotation axis.
|Publication status||Published - 2017 Nov 11|
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