Impact of Pressure on Metavalent Bonding in BiTe Influencing Electronic Topological Transitions

BiTe, a member of the (Bi₂)_m(Bi₂Te₃)_n homologous series, possesses natural van der Waals-like heterostructure with a Bi₂ bilayer sandwiched between the two [Te-Bi-Te-Bi-Te] quintuple layers. BiTe exhibits both the quantum states of weak topological and topological crystalline insulators, making it a dual topological insulator and a suitable candidate for spintronics, quantum computing and thermoelectrics. Herein, we demonstrate that the chemical bonding in BiTe is to be metavalent, which plays a significant role in the pressure dependent change in the topology of the electronic structure Fermi surface. The enhancement of the metavalent bonding character with pressure in BiTe is evidenced from first-principles density functional theory (DFT) calculations. Due to the change in the Fermi surface topology, we have visualized electronic topological transitions (ETT) at ~1 and ~3 GPa through pressure dependent synchrotron X-ray diffraction analysis and Raman spectroscopy. The correlation between the metavalent bonding and ETT offers insights into chemical bonding influenced transitions in quantum materials.