Conduction Band Parameters of Bi₂Se_e from Shubnikov‐de Haas Investigations

Abstract

The oscillatory magnetoresistance (Shubnikov-de Haas effect) was observed on n-type B&Se, single crystals between 1.6 and 4.2 K. The electron concentrations ranged from about 4 x 101' to 4 x lo1@ ~m -~. Stationary magnetic fields u p to 10.5 T were available.The angular dependence of the Shubnikov-de Haas periods revealed an almost rotational symmetry of the Fermi surface around the k,-axis with a small amount of trigonal warping.Perpendicular to the k,-axis for k, = 0 a parabolic e ( k i ) relation is found, parallel to the k,-axis a n increasing nonparabolicity is evaluated. Only above lOl0 electrons/cm3 the deviation of the shape of the Fermi surface from that of an ellipsoid of rotational symmetry becomes significant. The cyclotron mass m, perpendicular to the k,-axis (B j j c ) is determined to be 0.124 m,, in the whole concentration range. Fermi energies are evaluated up to 160 meV. The single-valley model for the lowest conduction band of Bi,Se, is con. firmed.Der oszillatorische Anteil der magnetischen Widerstandsanderung (Shubnikov-de HaasEffekt) wurde a n n-leitenden Bi,Se,-Einkristallen zwischen 1,6 und 4,2 K beobachtet.

Tuning carrier type and density in Bi2Se3 by Ca-doping

“…Although it is not possible to determine the effective masses for both electrons and holes independently, the reduced effective mass obtained from our experiments agrees with the value calculated from the electron and hole masses reported in published works. 10,11 Using the estimated effective electron mass ͑m e ‫ء‬ = 0.14 m e ͒ and the dielectric constant ͑ =3͒, we calculated the plasma frequency for a highdensity n-type sample ͑x = 0.5% and n 3D = 7.2ϫ 10 18 cm −3 ͒ to be ϳ700 cm −1 , which agrees well with the position of the plasma dip in the measured reflectance spectrum ͑ϳ611 cm −1 ͒.…”

Interband absorption edge in the topological insulators Bi2(Te1−xSex)3

“…18 cm −3 which is below the threshold of ≈ 10 19 cm −3 , above which a significant nonparabolicity of the conduction band has been observed 38 . Similarly, the valence band was reported 37 to have parabolic shape for the Fermi wavevector corresponding to our sample (k F,a ≈ 0.04Å −1 ).…”

Hole Fermi surface inBi2Se3probed by quantum oscillations

“…6 for sample B3. Simulations of the magnetoresistance were performed based on the simple phenomenological approach developed for the conduction band, 6,9 in which one considers a 3D electron gas with a large (spinorbit-enhanced) spin gap g * ef f µ B B, where g * is the effective hole g-factor. As can be seen in Fig.6 the measured (background-removed) oscillations exhibit a minimum at B ∼ 22.5 T, instead of the maximum expected from the g * = 0 (no spin-splitting) simulation based on the low field oscillation frequency (F = 55.8 T).…”