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

• Main Authors: Todd, Seth B, Riley, Drew B, Binai-Motlagh, Ali, Clegg, Charlotte, Ramachandran, Ajan, March, Samuel A, Hill, Ian G, Stoumpos, Constantinos C, Kanatzidis, Mercouri G, Yu, Zhi-Gang, Hall, Kimberley C
• Format: Journal Article
• Language: English
• Published: 27-07-2018
• Subjects: Physics - Materials Science
• DOI: 10.48550/arxiv.1807.10803

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.