arXiv subjects

Reshna Shrestha

Publications and source records attributed to Reshna Shrestha.

2 recordsLinked to original sources

arXiv2026

Impact of crystallinity on the circular and linear dichroism signals in chiral perovskite

Chiral perovskites owing to their broken mirror symmetry exhibit selective absorption of circularly polarized light manifesting a strong circular dichroism (CD). CD spectroscopy has been a key technique to understand chiral perovskites and how these semiconductors achieve chirality at the molecular level. However, there is a debate on whether the observed CD is intrinsic to the chiral crystal structures or is modulated by extrinsic phenomena particularly linear dichroism (LD) and linear birefringence (LB) effects. This work investigates the chiroptical properties of $(R-/S-\text{MBA})_2\mathrm{CuCl}_4$ (MBA = Methylbenzyl ammonium) series by thoroughly studying the contribution from LD and LB to the observed CD signals. The comparison of highly oriented and randomly oriented films exhibits notable LD and LB contributions to the observed CD, which are caused by orientation-dependent electric-field interactions and local anisotropy. Both randomly and highly oriented films exhibit distinct CD responses, with LD--LB effects largely dominating the CD in highly oriented films. This has been revealed by the obvious shift in the observed CD signals to the below-absorption-edge ($\sim 430$ nm) regime and broadening of features. Our findings demonstrate that careful consideration of crystal orientation and structural effects is necessary for appropriate interpretation of CD spectra in chiral perovskite thin films.

cond-mat.mtrl-sci↗

arXiv2025

Unconventional Spintronics from Chiral Perovskites

Spintronic devices typically employ heterostructures with ferromagnets which break time-reversal symmetry and have non-vanishing magnetization. With the growing class of materials that support spin-polarized carriers, current, and excitations,it is possible to envision emerging spintronic applications that are not limited to magnetoresistance. Here we focus on chiral perovskites with no net magnetization where the space-inversion and mirror symmetries are broken to induce chiral structure. The known importance of these perovskites is further expanded by the demonstration of the chiral-induced spin selectivity (CISS). However, the generation of the spin-polarized carriers across the interface with these chiral perovskites remains to be fully understood. Our first-principles studies for two-dimensional PbBr$_4$-based chiral perovskites provide their electronic structure and an orbital-based symmetry analysis, which allows us to establish an effective Hamiltonian to elucidate the underlying origin of their chirality. We also use this analysis for the Edelstein effect, responsible for electrical generation of the nonequilibrium spin polarization in many materials, which in chiral perovskites could be a mechanism contributing to CISS. Furthermore, by examining optical properties of chiral perovskites and the opportunity to use them to realize tunable altermagnets, another class of zero-magnetization spintronic materials, we put forth a versatile materials platform for unconventional spintronics.

cond-mat.mtrl-sci↗