Ultrafast Spin-to-Charge Conversion in Chiral Hybrid Organic-Inorganic Perovskites

Understanding charge-to-spin conversion allows efficient control and manipulation of the spin degree of freedom, which can pave the way for next generation spintronic materials. Chirality induced spin selectivity (CISS) describes a charge-to-spin conversion process such that when a charge current is passed through a chiral system the charge carriers become spin-polarized. Most demonstrations of CISS involve coupling chiral systems with ferromagnets and measuring the steady-state magnetoresistance (MR) to analyze the spin current. Large spin polarized currents are measured using a magnetic conductive AFM probe (mCP-AFM), however macroscopic MR measurements yield, so far, small MR responses. As a result there are no simple ways to compare and understand the charge-to-spin conversion process on the microscopic level. Here we demonstrate a non-contact measurement of inverse CISS (ICISS), which is the reciprocal process to CISS. In our ICISS measurements a time-varying spin current generates a time-varying charge current which is read out through terahertz (THz) emission spectroscopy. We studied ICISS in R/S-(MBA)₂PbI₄ thin films and for both R/S films we find that ICISS produces a THz waveform for both up and down spins but the phase is 180° different when either the chirality or the spin polarization changes. Interestingly we observe similar ICISS responses for both R/S-(MBA)₂PbI₄ even when the injected spin orientation is the same, but the current direction changes when the chirality changes. We describe these results in terms of a chiral spin splitting with spin texture along the chiral axis implying that CISS occurs due to spin polarization in these systems.