arXiv subjects

Chamini S. Pathiraja

Publications and source records attributed to Chamini S. Pathiraja.

3 recordsLinked to original sources

arXiv2026

RIXS Identification of Optical Phonon-Spin Coupling Effects in CrSBr

Resonant inelastic x-ray scattering provides experimental signatures of spin-phonon coupling in CrSBr through temperature-dependent Cr $L$-edge spectra. Low-energy excitations are observed exclusively in the low-temperature antiferromagnetic phase as energy-loss features. A quasi-elastic peak at approximately 42 meV is observed under $π$-polarization. Density functional theory phonon-mode calculations identify these RIXS features as occurring within the same energy range as bond-bending optical phonon modes associated with distortions of the Cr--S--Cr network. The pronounced suppression of these low-energy excitations upon warming into the paramagnetic phase, together with their polarization dependence, the calculated phonon spectrum, and a spin-renormalized electron-phonon RIXS framework, indicates a strong interplay between magnetic correlations and lattice dynamics. While the loss features appear at energies characteristic of optical phonons, the significant overlap of the optical-phonon and magnon bands suggests that the temperature-dependent behavior should not be regarded as purely lattice-derived excitations. Instead, the room-temperature suppression of the low-energy RIXS peaks is explained in terms of a spin-phonon coupling effect on the $L$-edge electron-phonon RIXS mechanism. The interpretation is supported by the combined experimental observations, phonon calculations, and theoretical modeling, rather than by temperature contrast alone. These results support spin-phonon coupling as a plausible and consistent interpretation of the observed temperature-dependent RIXS response and demonstrate that magnetic order can strongly influence phonon-related spectral weight in the RIXS spectrum.

cond-mat.mtrl-sci↗

arXiv2026

Trigonal Distortion Driven Ground States in VX3 (X = Br and I)

Transition-metal halides V$X_3$ ($X$ = Br and I) have emerged as promising candidates for two dimensional spintronic and quantum applications due to their layer-dependent magnetism and tunable electronic states. However, experimental insights into their ground state electronic structures remain limited. Here, we present a comprehensive investigation of V$X_3$ using high resolution resonant inelastic x-ray scattering (RIXS) combined with ligand field multiplet calculations. The RIXS spectra reveal distinct $dd$ and charge-transfer excitations, allowing precise determination of electronic structure parameters, including the crystal field splitting, trigonal distortion, and Racah parameters. The determined parameters showed clear variation, indicating an increase in covalency from Br to I. The trigonal distortion parameters $Δ_{D_{3d}}$ were determined to be -0.096 eV in VBr$_3$ and 0.07 eV in VI$_3$, indicating a sign opposition between the two compounds, reflecting good agreement with experimental RIXS data. Cluster model calculations yield a high-spin V$^{3+}$ $(S = 1)$ configuration, with an $e'^2_g$ ground state in VBr$_3$ and an $e'^1_ga^1_{1g}$ ground state in VI$_3$, consistent with trigonal elongation and compression, respectively. Our findings provide the most complete experimental determination of the low energy electronic structure in V$X_3$, offering valuable insights for designing 2D magnetic and spintronic materials based on vanadium halides.

cond-mat.mtrl-sci↗

arXiv2025

Electronic Energy Scales of Cr$X_3$ ($X$ = Cl, Br, and I) using High-resolution X-ray Scattering

Chromium tri-halides Cr$X_3$ ($X$ = Cl, Br, and I) have recently become a focal point of research due to their intriguing low-temperature,layer-dependent magnetism that can be manipulated by an electric field. This makes them essential candidates for spintronics applications. These magnetic orders are often related to the electronic structure parameters, such as spin-orbit coupling (SOC), Hund's coupling ($J_H$), $p-d$ covalency, and inter-orbital Coulomb interactions. Accurately determining such parameters is paramount for understanding Cr$X_3$ physics. We have used ultra high-resolution resonant inelastic x-ray scattering (RIXS) spectroscopy to study Cr$X_3$ across phase transition temperatures. Ligand field multiplet calculations were used to determine the electronic structure parameters by incorporating the crystal field interactions in a distorted octahedral with $C_3$ symmetry. These methods provide the most detailed description of Cr$X_3$ magneto-optical and electronic energetic (terms) to date. For the first time, the crystal field distortion parameters $Dσ$ and $Dτ$ were calculated, and the energies of $d$ orbitals have been reported. Our RIXS spectroscopic measurements reveal a clear energy separation between spin-allowed quartet states and spin-forbidden doublet states in Cr$X_3$. The role of SOC in Cr $2p$ orbitals for the spin-flip excitations has been demonstrated. The determined 10$Dq$ values are in good agreement with the spectrochemical series, and Racah B follows the Nephelauxetic effect. Such precise measurements offer insights into the energy design of spintronic devices that utilize quantum state tuning within 2D magnetic materials.

cond-mat.mtrl-sci↗