Tuneling of the Dislocations in Bcc ^3He Crystals

概要

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The attenuation and the velocity of the longitudinal sound wave in low densitybcc 'He crystals containing various amounts of 'He impurities from< 10 ppmto 1600 ppm were studied at various temperatures, sound frequencies and stressamplitudes. It was found that a large number of dislocations were multiplied bythe isotopic phase separation. Most of them are considered to be of screw type,and their irreversible motion causes the amplitude dependent attenuation andvelocity change. The critical shear stress amplitude above which the attenuationincreases does not depend on the 'He concentration nor on the temperature. Itsmagnitude is estimated to be r.=5 x 10 ' p, where p is the shear modulus. Becauser. is only 1/6 of the Peierls stress and independent of T, it is concluded that thescrew dislocations penetrate the Peierls potential barrier by turmeling under theapplied stress rho..
社団法人日本物理学会の論文
1983-03-15