Tellurium: Fast Electrical and Atomic Transport along the Weak Interaction Direction.

In anisotropic materials, the electrical and atomic transport along the weak interaction direction is usually much slower than that along the chemical bond direction. However, Te, an important semiconductor composed of helical atomic chains, exhibits nearly isotropic electrical transport between intrachain and interchain directions. Using first-principles calculations to study bulk and few-layer Te, we show that this isotropy is related to similar effective masses and potentials for charge carriers along different transport directions, benefiting from the delocalization of the lone-pair electrons. This delocalization also enhances the interchain binding, and thus facilitates diffusion of vacancies and interstitial atoms across the chains, which together with the fast intrachain diffusion enable rapid self-healing of these defects at low temperature. Interestingly, the interstitial atoms diffuse along the chain via a concerted rotation mechanism. Our work reveals the unconventional properties underlying the superior performance of Te while providing insight into the transport in anisotropic materials.