Zuyu Zhao

Shubnikov–de Haas effect in thin epitaxial films of gray tin

The transverse magnetoresistance and Hall effect have been studied for n‐type gray tin epilayers grown on (001)CdTe substrates by the molecular beam epitaxy technique. Shubnikov–de Haas oscillations were observed in samples having Hall mobilities ≥104 cm2 /Vu2009s at low temperatures. Measurements were carried out using both the dc method and field modulation techniques in the temperature range from 1.2 to 10 K and in magnetic fields up to 10 T. Beat patterns were observed in the Shubnikov–de Haas spectra which we ascribe either to inhomogeneous doping, arising from the diffusion of Cd and Te from the substrate, or to quantization of the motion in the direction parallel to the film normal. The Shubnikov–de Haas carrier concentration of a 1210 A film was determined to be nSdH =2.3×1017 cm−3, in good agreement with the Hall density.

Sound propagation in superfluid 3He B

Abstract This review describes sound propagation in the normal state and the superfluid B phase of 3He. The l=1 nature of Cooper pairing in superfluid 3He leads to a complex collective mode spectrum. A number of the collective modes couple to sound. The expressions for the collective mode frequencies are derived using a phenomenological theory. Cryogenic and ultrasonic measurement techniques are briefly discussed, followed by a review of the results of sound propagation experiments, in particular those that show coupling to the collective modes. The effects of fields, textures and dispersion are also reviewed.

A novel technique to measure the group velocity of sound in dispersive media

A technique is proposed for measuring the group velocity of sound by a frequency-modulated (FM) continuous wave (CW) technique. Detailed calculations are presented, showing that V/sub g/=( delta omega /sub m// delta phi )d, where V/sub g/, delta omega /sub m/, delta phi , and d are, respectively, the group velocity, change of modulation frequency, phase change of the received signal detected by a biphase lock-in amplifier, and the distance traveled by the sound. The approach has the advantage of high resolution compared to the conventional time-of-flight measurement technique.<<ETX>>

Growth and characterisation of substrate-stabilised heteroepitaxial grey tin films

The authors report molecular beam epitaxy growth of grey tin films on (001)CdTe substrates. The transverse magnetoresistance and Hall effect have been studied. Films thinner than 400 AA are p-type with carrier densities of (1-2)*1019 cm-3; thicker films are n-type with carrier densities as low as 2*1017 cm-3 Shubnikov-de Haas (SDH) oscillations are observed in samples having Hall mobilities >or=104 cm2 V-1 s-1 at low temperatures. Beat patterns are observed in the SDH spectra, which they ascribe to either inhomogeneous doping, arising from the diffusion of Cd and Te from the substrate, or quantisation of the motion in the direction parallel to the film normal. For field directions at 45 degrees and 90 degrees to the film plane normal, clear SDH oscillations are also observed at fields much lower than the expected size effect cut-off field, implying that specular reflection at the film boundaries plays a significant role.

Magnetic-field-dependent sound attenuation in UPt3

Abstract We report measurements of the attenuation of transverse sound along the c axis of UPt 3 . The peak in attenuation, which has previously been observed in longitudinal sound measurements vs . magnetic field in the superconducting state, is absent in the transverse sound measurements. We also present results on the magnetic-field-dependent attenuation in the normal state, up to 8 T. The attenuation increases with magnetic field, approximately as H 2 .