Deep Ultraviolet Optical Anisotropy of ß-Gallium Oxide Thin Films.

ß-Crystalline phase gallium oxide (ß-Ga2O3) is an ultrawide bandgap material with prospective applications in electronics and deep ultraviolet (DUV) optoelectronics and optics. The monoclinic crystal structure of ß-Ga2O3 results in optical anisotropy to incident light with different polarization states. This attribute can lead to different optical applications in the DUV. In this article, we investigated the optical properties of ß-Ga2O3 thin films grown by pulsed laser deposition technique on sapphire substrates with different crystallographic orientations. Marked in-plane polarization anisotropy, determined by reflectance and Raman spectroscopy, was observed for ß-Ga2O3 films deposited on an r-cut sapphire substrate. In contrast, isotropic optical properties were observed in ß-Ga2O3 films deposited on a c-cut sapphire substrate.

Spin-Phonon Coupling in Iron-Doped Ultrathin Bismuth Halide Perovskite Derivatives.

Spin in semiconductors facilitates magnetically controlled optoelectronic and spintronic devices. In metal halide perovskites (MHPs), doping magnetic ions is proven to be a simple and efficient approach to introducing a spin magnetic momentum. In this work, we present a facile metal ion doping protocol through the vapor-phase metal halide insertion reaction to the chemical vapor deposition (CVD)-grown ultrathin Cs3BiBr6 perovskites. The Fe-doped bismuth halide (Fe:CBBr) perovskites demonstrate that the iron spins are successfully incorporated into the lattice, as revealed by the spin-phonon coupling below the critical temperature Tc around 50 K observed through temperature-dependent Raman spectroscopy. Furthermore, the phonons exhibit significant softening under an applied magnetic field, possibly originating from magnetostriction and spin exchange interaction. The spin-phonon coupling in Fe:CBBr potentially provides an efficient way to tune the spin and lattice parameters for halide perovskite-based spintronics.

Spin-orbit exciton-induced phonon chirality in a quantum magnet.

The interplay of charge, spin, lattice, and orbital degrees of freedom in correlated materials often leads to rich and exotic properties. Recent studies have brought new perspectives to bosonic collective excitations in correlated materials. For example, inelastic neutron scattering experiments revealed non-trivial band topology for magnons and spin-orbit excitons (SOEs) in a quantum magnet CoTiO3 (CTO). Here, we report phonon properties resulting from a combination of strong spin-orbit coupling, large crystal field splitting, and trigonal distortion in CTO. Specifically, the interaction between SOEs and phonons endows chirality to two [Formula: see text] phonon modes and leads to large phonon magnetic moments observed in magneto-Raman spectra. The remarkably strong magneto-phononic effect originates from the hybridization of SOEs and phonons due to their close energy proximity. While chiral phonons have been associated with electronic topology in some materials, our work suggests opportunities may arise by exploring chiral phonons coupled to topological bosons.