Relation between the topology of the elementary energy bands in the valence band of the Hg₃TeCl₄ crystal and its anisotropy

Abstract

A mechanism of the Davydov‐like splitting formation in the Brillouin zone of the Hg3TeCl4 crystal (Pbca, D2h15) with two double translationally nonequivalent layers in the unit cell was analyzed. The topology of the 8‐branch elementary energy bands creating the valence band of Hg3TeCl4 was explained. Energetic distances between states of the elementary energy bands at the Brillouin zone edges were estimated by means of the localized function method. The topology of the elementary energy bands was related with the ratio of the interaction strength between the double layers in the unit cell and the interaction strength between single layers creating the double layer. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Non‐standard anisotropy of the energy spectrum of a layered TlGaSe2 crystal

“…Hence, the anisotropy of the valence band top is ‘anomalous’, while the lower branch exhibits a ‘normal’ anisotropy. Such a behaviour was observed for some valence band branches of a complicated Hg 3 TeCl 4 crystal 28, 34. It was demonstrated that there is no universal anisotropy of bonding for particular orbitals in different directions in r ‐space.…”

Band Structure and Optical Properties οf the Layered Hg3TeCl4Crystal

“…Mechanical properties of the crystal as well as the X-ray investigations point to its layered properties, there are 64 atoms in the unit cell which are arranged into two double, translationally non-equivalent layers perpendicular to the y axis. It was shown that the anisotropy of the overlap of electron wave functions is different in various energy ranges and leads to the Davydov splittings in the band structure, in particular in the Γ point of the conduction band [2,3]. Hence, the anisotropy of the electron and hole effective masses does not correspond to the mechanical anisotropy of the crystal and it is not typical for layered crystals (m 2 (hν) dependence points to the presence of the direct optical transitions in the crystal which is in agreement with the theoretical band structure calculations.…”