Phonon generation coefficient and nonreciprocity of the bismuth current-voltage characteristic

Comparison of the bismuth current-voltage characteristic with a theoretical formula which contains the phonon generation coefficient in explicit form provides information on the generation coefficient's dependence on temperature and magnetic field. The theoretical formula obtained in the present study together with the temperature dependence of the generation coefficient easily explains the anomalous temperature behavior of magnetoresistance oscillation amplitude in the nonlinear regime {Yu. A. Bogod and R. G. Valeev, Fiz. Nizk. Temp. 2, 897 (1976) [Sov. J. Low Temp. Phys. 2; Solid State Commun. 20, (1976)] 1061 (1976)}. Oscillations of the generation coefficient and consideration of Fermi surface anisotropy permit suggestions as to the causes of new features of the bismuth nonreciprocity effect observed in this study. (The nonreciprocity effect is the nonreproducibility of the nonlinear segment of the current-voltage characteristic in a reversed magnetic field H). New features discovered are the equivalence of reversing magnetic and electric fields; the nonmonotonic dependence on H of the difference in electric field intensity within the specimen Δ E(H) = E(H)−E(—H) for a given current value: change in sign of ΔE at certain H values; the possibility of suppressing or exciting instability by reversing the direction of charge carrier drift velocity. Calculation of electron drift velocities in the ellipsoidal Fermi surface approximation permitted explanation of the deviation of the current-voltage characteristic from Ohm's law even at cE/H ≈ 0.5s (where s is the speed of sound), which was observed in the present study.

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