A New Phenomenon is Sound Attenuation in Bismuth under Very Strong Magnetic Fields

A new phenomenon in sound attenuation in bismuth has been observed at liquid helium temperatures and under very strong magnetic-field conditions such that the electrons and holes in the states with the Landau quantum number n =1 almost simultaneously satisfy resonance when varing the field strength in some suitable field directions. The anomalous part of the attenuation at the resonance field position, Δ α, obeys the law Δ α= A ( T / T c -1) -(0.49±0.06) in a limited region of reduced temperature ( T / T c -1). The values of the parameters T c (\({}1.6\) K) and A depend characteristically on the difference between the resonance field strengths for the electrons and holes. The experimental facts suggest that this phenomenon may be related to the fluctuation of electron-hole pairs produced above the excitonic phase transition temperature.