Abstract
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 αR; it is desirable to manipulate αR to control the functional properties. The current work illustrates how αR 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 αR in doped BiTeI can be manipulated within the range of 0–4.05 eV Å by doping different elements. The dopants change αR by affecting both the spin–orbit coupling strength and band gap. Some dopants with low atomic masses give rise to unexpected and sizable αR, mainly due to the local strains. The calculated electrical transport properties reveal an optimal αR range of 2.75–3.55 eV Å for maximizing the thermoelectric power factors. αR 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.
Highlights
The Rashba effect plays a critical role in controlling the electronic structure and the functional properties of semiconductors, including topological insulators and thermoelectrics[1,2,3,4,5,6,7]
Because the Rashba effect changes the electronic structures, there can be strong effects on the electrical transport properties of thermoelectrics. This can occur through modification of the density of states (DOS)[23] and presumably through changes in dispersion relations, both of which are important for the electrical resistivity
The original degenerate band structure without spin–orbit coupling (SOC) (Fig. 1a dotted line) of BiTeI is subject to sizable Rashba spin splitting, characterized by αR = 2E0/|k0| (Fig. 1a solid line), at both the conduction band minimum (CBM) and the valence band maximum (VBM) (Supplementary Fig. 1b), centered at the A point, as shown
Summary
The Rashba effect plays a critical role in controlling the electronic structure and the functional properties of semiconductors, including topological insulators and thermoelectrics[1,2,3,4,5,6,7]. Because the Rashba effect changes the electronic structures, there can be strong effects on the electrical transport properties of thermoelectrics This can occur through modification of the density of states (DOS)[23] and presumably through changes in dispersion relations, both of which are important for the electrical resistivity. The thermopower, in the numerator, and the electrical resistivity, in the denominator, are both positively correlated with the DOS This reflects the fact that in a parabolic band model, a higher effective mass leads to enhanced S. Based on these results and the mapping between the composition and αR, a few promising Rashba thermoelectrics are proposed.
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