Defect-mediated Rashba engineering for optimizing electrical transport in thermoelectric BiTeI

The Rashba effect plays a vital role in electronic structures and related functional properties. The strength of the Rashba effect can be measured by the Rashba parameter alpha(R); it is desirable to manipulate alpha(R)to control the functional properties. The current work illustrates how alpha(R)can be systematically tuned by doping, taking BiTeI as an example. A five-point-spin-texture method is proposed to efficiently screen doped BiTeI systems with the Rashba effect. Our results show that alpha(R)in doped BiTeI can be manipulated within the range of 0-4.05 eV angstrom by doping different elements. The dopants change alpha(R)by affecting both the spin-orbit coupling strength and band gap. Some dopants with low atomic masses give rise to unexpected and sizable alpha(R), mainly due to the local strains. The calculated electrical transport properties reveal an optimal alpha(R)range of 2.75-3.55 eV angstrom for maximizing the thermoelectric power factors.alpha(R)thus serves as an effective indicator for high-throughput screening of proper dopants and subsequently reveals a few promising Rashba thermoelectrics. This work demonstrates the feasibility of defect-mediated Rashba engineering for optimizing the thermoelectric properties, as well as for manipulating other spin-related functional properties.