Strong interlayer coupling in monoclinic GaTe

Abstract

Recently, emerging intriguing physical properties have been unraveled in anisotropic layered semiconductors, with their in-plane anisotropy often originated directly from the low crystallographic symmetry. However, little has been known in the case where interlayer couplings dominate the anisotropy of electronic band structures in them. Here, by both experiment and theory, we show rather than geometric factors, the anisotropic energy bands of monoclinic gallium telluride (GaTe) are determined by a subtle bulk-surface interaction. Bulk electronic states are found to be the major contribution of the highest valence band, whose anisotropy is yet immune to surface doping of potassium atoms. The above peculiar behaviors are attributed to strong interlayer couplings, which gives rise to an inverse of anisotropy of hole effective masses and a direct-indirect-direct transition of band gap, depending on the number of layers. Our results thus pave the way for future applications of anisotropic layered semiconductors in nanoelectronics and optoelectronics.Comment: 3 figure