Coherent spin dynamics of electrons and holes photogenerated with large kinetic energy in lead halide perovskite crystals

TL;DR

This study investigates the coherent spin dynamics of electrons and holes in lead halide perovskite crystals, revealing long spin dephasing times and demonstrating all-optical control of spin signals at cryogenic temperatures.

Contribution

It provides new insights into spin relaxation processes and demonstrates all-optical manipulation of spin states in perovskite materials.

Findings

Nanosecond spin dephasing times at 1.6 K

Inefficient spin relaxation during energy relaxation

All-optical control of spin signals achieved

Abstract

The coherent spin dynamics of electrons and holes are studied in a FA0.9Cs0.1PbI2.8Br0.2 perovskite bulk crystal, using time-resolved Kerr ellipticity in a two-color pump-probe scheme. The probe photon energy is tuned to the exciton resonance, while the pump photon energy is detuned from it up to 0.75 eV to higher energies. The spin-oriented electrons and holes photogenerated with significant excess kinetic energy relax into states in vicinity of the band gap, where they undergo Larmor precession in an external magnetic field. At cryogenic temperatures down to 1.6 K, the spin dephasing time reaches the nanosecond range. During energy relaxation, the carrier spin relaxation is inefficient and only happens when the carriers become localized. In experiments with two pump pulses, all-optical control of the amplitudes and phases of the electron and hole spin signals is achieved in the additive regime by varying the intensities of the pump pulses and the time delay between them.