de Haas-van Alphen Effect inn-TypeBi2Te3

The de Haas-van Alphen (dHvA) effect has been measured in $n$-type ${\mathrm{Bi}}_2$ ${\mathrm{Te}}_3$ with carrier concentrations ranging from 9×${10}^{17}$ to 2.4×${10}^{19}$ ${\mathrm{cm}}^{-3\mathrm{}}$. Below 5×${10}^{18}$ ${\mathrm{cm}}^{-3\mathrm{}}$, the conduction-band minima can be fitted to a six-ellipsoid model, the parameters of which differ considerably from those inferred from magnetoresistance experiments. The carrier density computed from the volume of the ellipsoids agrees well with that obtained from the limiting high-field Hall coefficient at 4.2°K. At higher concentrations there is a large discrepancy between the two estimates of carrier density. The presence of a low-mobility high-mass band, lying 30 meV above the ellipsoidal minima, is postulated to explain the difference. The existence of this second band or of an anisotropic relaxation time are possible explanations of the discrepancy between the ellipsoidal parameters deduced from the dHvA and transport measurements.