Pulse Responses of Nonlinear Magnetoresistance in Bismuth

Nonlinear magnetoresistance in bismuth is studied at 4.2°K with fast rise time pulses in a steady magnetic field up to 16 kOe. For 50–100 nsec pulses, ohmic relations are obtained up to E 0 ∼5(sH/c), and the predicted hot electron effect is found to be negligibly small. It turns out that the strong nonlinearity discovered by Esaki takes place after a finite time τ b corresponding to buildup of a phonon flux due to the ultrasonic amplification. Two different types of magnetic field dependence of τ b are observed, namely, τ b ∝ H -2 for τ b ≫ d / s , and τ b ∝ H -1 for τ b ≪ d / s , where d / s is the transit time of the phonon flux across the sample. Continuous oscillations are observed whose period is considerably smaller than the round-trip time of the phonon flux.

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