Temperature emerges as a control for topological properties of materials
Spin-orbit coupling (SOC), an interaction between an electron's spin and its motion, plays a key role in creating topological insulators—unusual materials that are insulating in their interior but can conduct electricity along their surfaces.
Temperature plays a crucial role in shaping the topological properties of certain materials, according to a new study. The research, led by Professor Sun Yiyang from the Shanghai Institute of Ceramics, reveals that increasing temperature weakens the spin-orbit coupling (SOC) in the topological insulator Bi2Se3, leading to a transition to a normal insulating state.
SOC, an interaction between an electron's spin and its motion, typically determines the formation of topological insulators. However, this study challenges the notion that SOC is solely intrinsic to a material's atomic species. Instead, researchers found that temperature causes SOC to weaken, which in turn reduces the band gap correction by up to 0.19 eV and suppresses the band inversion necessary for topological order.
At temperatures above 500 K, the researchers observed the emergence of trivial, non-topological structures, marked by the loss of surface Dirac cones. Molecular dynamics simulations confirmed that thermal expansion alone could not account for this transition; rather, the weakening of SOC due to rising temperatures was the primary driver. Similar temperature-dependent behavior was observed in other topological insulators, Bi2Te3 and Sb2Te3.
This groundbreaking work has significant implications for controlling electronic properties of materials, with potential applications in emerging fields like spintronics and quantum computing.
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