Detection of Rashba spin splitting in 2D organic-inorganic perovskite via precessional carrier spin relaxation

TL;DR

This study confirms the presence of Rashba spin splitting in a 2D organic-inorganic perovskite using time-resolved circular dichroism, revealing a significantly larger splitting than in traditional semiconductors, with implications for spintronics.

Contribution

First experimental confirmation of Rashba spin splitting in a 2D perovskite via carrier spin dynamics analysis, quantifying the effect with a novel measurement approach.

Findings

Rashba spin splitting of 10 meV was observed in the 2D perovskite.

The Rashba effect in this material is 20 times larger than in GaAs quantum wells.

Precessional spin relaxation dominated the spin dynamics, confirming Rashba influence.

Abstract

The strong spin-orbit interaction in the organic-inorganic perovskites tied to the incorporation of heavy elements (\textit{e.g.} Pb, I) makes these materials interesting for applications in spintronics. Due to a lack of inversion symmetry associated with distortions of the metal-halide octahedra, the Rashba effect (used \textit{e.g.} in spin field-effect transistors and spin filters) has been predicted to be much larger in these materials than in traditional III-V semiconductors such as GaAs, supported by the recent observation of a near record Rashba spin splitting in CH$_3$NH$_3$PbBr$_3$ using angle-resolved photoemission spectroscopy (ARPES). More experimental studies are needed to confirm and quantify the presence of Rashba effects in the organic-inorganic perovskite family of materials. Here we apply time-resolved circular dichroism techniques to the study of carrier spin dynamics in a 2D perovskite thin film [(BA)$_2$MAPb$_2$I$_7$; BA = CH$_3$(CH$_2$)$_3$NH$_3$, MA = CH$_3$NH$_3$]. Our findings confirm the presence of a Rashba spin splitting via the dominance of precessional spin relaxation induced by the Rashba effective magnetic field. The size of the Rashba spin splitting in our system was extracted from simulations of the measured spin dynamics incorporating LO-phonon and electron-electron scattering, yielding a value of 10 meV at an electron energy of 50 meV above the band gap, representing a 20 times larger value than in GaAs quantum wells.