Magnetophonon Resonance of Hot Electrons inn-InSb at 77°K

Abstract

PHYSICAL REVIEW LETTERS 24APRIL1972elastic-constant data, 5 is very similar. We can make an estimate for the distance in energy that the second band lies below E ¥ at absolute zero from Schirber and Switendick's volume-dependent band calculation. 7 This gave a difference between the increase in energy of the second band at T and the energy of the other bands at L of 0.067 V with ~30 kbar. Assuming this difference is a measure of the rate at which the second band moves relative to E F , this equates -0.002 V to 1 kbar and puts the band ~0.012 V below the Fermi energy at absolute zero. This value is roughly consistent with the thermal behavior of the Knight shift and elastic-constant data which change in a temperature region centered around 80 K or ~ 0.007 V. This reasoning also indicates that the peak in the density of states is quite sharp (width at half-height of perhaps 0.005 V) since T c drops appreciably between 6 and 8 kbar.In conclusion, we feel that the combination of the unusual pressure dependence of the thirdzone Fermi-surface cross sections and the almost discontinuous pressure dependence of the superconducting transition temperature argue very strongly for a pressure-induced electron transition in AuGag. Such a transition supports both the experimental inference from the studies of AuGag, AuALj, and Aula^ series a*id the theoretical predictions of Schirber and Switendick's volume-dependent band model. We further propose that the anomalous temperature dependence of magnetic properties of AuGa^j stems from a purely thermal depopulation of the second band, thus requiring no explicit phonon effects such as suggested earlier. 7 The technical assistance of R. L. White is gratefully acknowledged, as are helpful discussions with A. C. Switendick, J. P. Van Dyke, and A. Narath.Magnetophonon resonances in the hot-electron mobility have been observed in pure n-InSb at 77°K in transverse magnetic fields with the application of sufficiently small voltage to produce a slight change in the mobility. The minima in the quantity /3 in the formula A* =Mo(l -fiE 2 ) are attributed to resonant cooling of hot electrons due to optical-phonon-induced transitions between Landau levels.We report here a new type of resonance experiment consisting of the observation of magnetophonon resonances in the hot-electron mobility in w-InSb at 77°K. Magnetophonon resonances were first predicted by Gurevich and Firsov, 1 and subsequently confirmed experimentally by many workers. 2 Magnetophonon phenomena in the electrical resistance reflect the resonant inelastic scattering of electrons between the high densities of states in Landau levels close to k 9 1129

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