Doppler-shifted acoustic cyclotron resonance in indium

Abstract

The Fermi surface (FS) in In was investigated by the method of the Doppler-shifted cyclotron-resonance absorption of longitudinal sound (100-300 MHz) in magnetic fields from 0.5 to 50 kG. Extremal values of $|\frac{\ensuremath{\delta}{A}_{\ensuremath{\perp}}({k}_{B})}{\ensuremath{\delta}{k}_{B}}|$ were determined: ${A}_{\ensuremath{\perp}}({k}_{B})$ is the area of cross section of the FS perpendicular to $\stackrel{\ensuremath{\rightarrow}}{B}$ through the end of the vector ${k}_{B}\stackrel{^}{B}$. The sonic absorption was measured by the pulse-echo method. In has a fct structure. $\stackrel{\ensuremath{\rightarrow}}{\mathrm{q}}$ was parallel to [001], [100], and [110] directions. $\stackrel{\ensuremath{\rightarrow}}{B}$ was varied in the (010), (001), and (110) planes. None of the observed absorption resonances appears to originate on the second-zone Fermi-hole surface. The most consistent interpretation of the Doppler-shifted acoustic cyclotron resonances (DSACR) is that they arise from the third-zone electron FS, including both the $\ensuremath{\alpha}$ and $\ensuremath{\beta}$ arms. In most, but not all, of the investigations of the FS in In by other methods, the $\ensuremath{\alpha}$ arms have not appeared. Local pseudopotential models for In have been based on the assumption that the $\ensuremath{\alpha}$ arms do not exist or are very small. While the existence of the $\ensuremath{\alpha}$ arms is not proven their existence is supported by this investigation. The amplitude of one series of DSACR oscillations was observed to decrease linearly with $T$.