Mode locking of hole spin coherences in CsPb(Cl,Br)$_3$ perovskite nanocrystals

TL;DR

This study demonstrates mode locking of hole spin coherences in CsPb(Cl,Br)$_3$ perovskite nanocrystals, revealing long coherence times and the influence of nuclear interactions, with implications for spintronics.

Contribution

It provides the first experimental observation and theoretical modeling of spin mode locking and nuclear focusing effects in perovskite nanocrystals.

Findings

Spin mode locking observed in perovskite nanocrystals.

Measured hole spin coherence time of 13 ns.

Theoretical model accurately describes experimental data.

Abstract

The spin physics of perovskite nanocrystals with confined electrons or holes is attracting increasing attention, both for fundamental studies and spintronic applications. Here, stable CsPb(Cl$_{0.5}$Br$_{0.5}$)$_3$ lead halide perovskite nanocrystals embedded in a fluorophosphate glass matrix are studied by time-resolved optical spectroscopy to unravel the coherent spin dynamics of holes and their interaction with nuclear spins of the $^{207}$Pb isotope. We demonstrate the spin mode locking effect provided by the synchronization of the Larmor precession of single hole spins in each nanocrystal in the ensemble that are excited periodically by a laser in an external magnetic field. The mode locking is enhanced by nuclei-induced frequency focusing. An ensemble spin dephasing time $T_2^*$ of a nanosecond and a single hole spin coherence time of $T_2=13\,$ns are measured. The developed theoretical model accounting for the mode locking and nuclear focusing for randomly oriented nanocrystals with perovskite band structure describes the experimental data very well.