Tellurium: Fast Electrical and Atomic Transport along 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 comprised of helical atomic chains, exhibits nearly isotropic electrical transport between intra-chain and inter-chain directions. Using first-principles calculations to study the bulk and few-layer Te, we show that this isotropy is related with similar effective mass and potential for charge carriers along different transport directions, benefiting from the delocalization of the lone-pair electrons. This delocalization also enhances the inter-chain binding, although it is still significantly weaker than the covalent intra-chain bonding. Moreover, we find a fast diffusion of vacancies and interstitial atoms along and across the chains, enabling rapid self-healing of these defects at room 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.