Commutation Effect in Bismuth Type Semimetals

Abstract

The dependence of the Nernst-Ettingshausen longitudinal effect on the direction of the magnetic field for the case of semimetals is studied theoretically and experimentally. A quite unique correspondence is found between the anisotropy of the effect and the band structure near the Fermi level. It is shown that the commutation effect which determines the dependence of the magneto-thermo-e.m.f. magnitude on the direction of the induction vector, permits to judge about the number and localization of band extrema in the k-space. This is an effective way for studying band structures of bismuth and its alloys a t high temperatures. The results of CE studies in bismuth and its alloys art 100 O K are given below. Theory of Thermomagnetic EffectsThe expression for the electric current density J is given as follows :where oi,(B) is the generalized electroconductivity tensor, E, the electric field, 0, T the temperature gradient.The tensor Pir(B) is determined by the correlation

The Nernst‐Ettingshausen Effect in Bismuth under the Influence of Directed Deformation

“…. ( B ) = -d ( B ) a l j ( B ) .it is clear that the %ommutationalTT effect may be determined in general by the components of the tensors 6.. and p.. , which differ from zero if the orientation of the main axis of the isoenergetic surfaces of a t least one from the charge carr i e r groups (in our case L -electrons) did not coincide with the basic nrystallographic directions(6).…”

Thermo- and magneto-thermo-E.M.F. in Bi-Sn alloys

“…Rotation curves of Aa/a at 2 and 10 kG ( Fig. 3) possess a structure similar to pure Bi (10,11). This is natural because, according to the theory developed in (ll), the structure is determined by the slope of the Fermi-ellipsoids of electrons with respect to the trigonal crystal plane.…”

Some features of the transverse thermomagnetic effect in bismuth

“…The angular dependence of the transverse N-E effect was determined by the way of automatic recording of electric field components E , and E , [2]. The total N-E field was obtained by geometrical summation of these components.…”

“…2), it can be directly explained by use of the results published in [2]. For better illustration we shall assume the dispersion law in the conduction band to be quadratic and the relaxation time to be energy independent.…”