Spin-orbit enhanced carrier lifetimes in noncentrosymmetric semiconductors

TL;DR

This paper demonstrates that spin-orbit coupling in noncentrosymmetric semiconductors can significantly alter carrier recombination rates, with potential to control material photophysics, supported by large-scale DFT screening and detailed analysis of selected materials.

Contribution

It introduces a novel mechanism linking spin-orbit coupling to carrier lifetime modification and identifies candidate materials exhibiting this effect through extensive computational screening.

Findings

Transition dipole moments can be enhanced by up to three orders of magnitude.

Carrier recombination rates can be either increased or decreased by spin-orbit effects.

Three candidate materials exemplify the range of behaviors observed.

Abstract

We show that the carrier recombination rate of noncentrosymmetric materials can be strongly modified by spin-orbit coupling. Our proposed mechanism involves the separation of conduction and valence bands into their respective spin components, which changes the transition dipole moments between them. The change in the carrier recombination can be either positive or negative in sign, or vary depending on the location of carriers in the Brillouin zone. We have performed a large scale DFT screening study to identify candidate materials that display this effect. We have selected three materials, Pb$_4$SeBr$_6$, ReTe$_3$Br$_5$, and CsCu(BiS$_2$)$_2$, which span the range of behaviors, and discuss their electronic band structure in greater detail. We find transition dipole moment enhancement factors of up to three orders of magnitude, reflecting the physical impact of spin-orbit coupling on the carrier lifetime. Therefore, further explorations of the spin-orbit coupling and lattice symmetry could prove to be useful for manipulating the photophysics of materials.