Non-resonant spin injection of exciton-polaritons with halide perovskites at room temperature

TL;DR

This work demonstrates room-temperature non-resonant spin control of exciton–polaritons in a halide-perovskite-based Tamm-plasmon cavity by embedding a 2D perovskite and tuning detuning via a PMMA spacer. Using angle-resolved spectroscopy and polarization tomography, the authors observe LPB dispersions with a vacuum Rabi splitting of $Ω_R = 38$ meV and reveal that circular non-resonant pumping injects spins that partially survive relaxation to the LPB, yielding a measurable $⟨S_3⟩$ across detunings, while bare excitons show no spin memory. The results highlight the fast polariton lifetime, enabling spin memory retention in the polariton channel, and point to halide perovskites as a viable platform for RT spinoptoelectronic devices such as chiral lasers and switches. The study lays groundwork for further RT spin control by exploring materials with longer spin lifetimes and advanced cavity architectures to enhance spin coherence in polaritonic systems.

Abstract

Exciton-polaritons, hybrid photon-exciton quasiparticles, constitute a useful platform for the study of light-matter interaction and nonlinear photonic applications. In this work, we realize a monolithic Tamm-plasmon microcavity embedding a thin film of two-dimensional halide perovskites with a tunable polymer spacer that controls the exciton-photon detuning. Angle-resolved optical spectroscopy at room temperature reveals the lower polariton branch dispersions in the linear regime for several detunings. Under circularly polarized, non-resonant laser excitation, the spin injection of high-energy excitons and their relaxation towards the lower polariton branch demonstrates its preservation, in contrast to the bare exciton case. The spin-polarized emission survives due to the fast decay of polaritons. Our results provide promising insights into the non-resonant spin control of polaritonic devices, including chiral lasers and switches.

Figures (10)

• Figure 1: (a) Sketch of the sample consisting of a monolithic Tamm-plasmon structure (a thin silver layer of around 35 nm, and a DBR consisting of 8 SiO$_2$/TiO$_2$ Bragg pairs), the spacer is composed by PMMA (with tunable thickness between 45-105 nm) and a 50 nm thick layer of (PEA)$_2$PbI$_4$. (b) Scheme of the non-resonant excitation scheme used in this work. The left side profile is the microcavity reflectivity plotted against energy (vertical axis). The right part of the panel presents the polariton dispersion relation (light blue UPB and LPB dispersion relations), and the exciton dispersion (gray color) at larger momentum wavevectors (represented in log-scale).
• Figure 2: LPB dispersion relation for three exciton-photon detunings, each panel shows the white light reflectivity (left) and PL emission (right) under non-resonant laser excitation (at 3.07 eV). The detunings of each column are 5, -50 and -95 meV, respectively; the Rabi splitting is $\Omega_R{=}38$ meV. The fitted bare cavity and exciton modes are indicated with dashed lines, the polariton modes (full lines) are fittings resulting from the two-mode coupling model. The (a-c) excitation power density in PL experiments has been 40.5, 42.8 and 32.1 $\mu$W/$\mu$m$^2$, respectively.
• Figure 3: Non-resonant spin injection in the LPB dispersion relation at RT, for three detunings: (a,d) -22 meV, (b,e) -50 meV, (c,f) -126 meV. (a-c) $S_3$ of the LPB dispersion relation under $\sigma^-$/$\sigma^+$ laser excitation in the left/right side of each panel, respectively. (d-f) Corresponding polarization purity under the same excitation conditions.
• Figure 4: Intensity-averaged values of $\langle S_3\rangle$ (a) and $\langle P\rangle$ (b) for the three different detunings and three polarized excitations ($\sigma^\pm$ and $H$) shown in Fig. \ref{['fig:disp_rel_S3_P']}.
• Figure 5: Custom-built optical setup for PL, white light reflectivity and polarization tomography experiments. It includes a CW violet laser for non-resonant excitation and a broadband white-light source for reflectivity measurements. Polarization control and full k-space characterization are enabled by a 0.75 NA objective, polarization optics, and a k-lens for switching between real- and momentum-space imaging. Emission is analyzed via a spectrometer and CCD for energy- and angle-resolved detection.