arXiv subjects

Prasanta Kumar Saikia

Publications and source records attributed to Prasanta Kumar Saikia.

3 recordsLinked to original sources

arXiv2026

Influence of Ni Doping on the Structural, Morphological, Optical, and Electrical Properties of Nanocrystalline Cd1-xMnxS Thin Films

Ni-doped Cd1-xMnxS (x=0.4) thin films were prepared via a cost-effective chemical bath deposition (CBD) method to investigate their suitability for optoelectronic applications. Incorporation of a secondary transition metal such as Ni is expected to influence lattice strain, defect density, and electronic structure through ionic size effects and sp-d exchange interactions, thereby providing an additional degree of freedom for tuning the properties of Cd1-xMnxS-based ternary systems. X-ray diffraction (XRD) analysis confirmed the cubic zinc blende structure of the Cd1-xMnxS crystal, which was further corroborated by high-resolution transmission electron microscopy (HRTEM). Crystallinity increases where as microstrain and dislocation density found to be decreases as the doping concentration of Ni increases. Field emission scanning electron microscopy (FESEM) analysis revealed uniform, dense, and crack-free films with grain size increasing as a function of Ni content, and the FESEM cross-sectional images indicated a nearly constant thickness in the range of 181.2-189.1 nm. The films exhibited high optical transmittance (75-90%) in the visible and near-infrared (NIR) regions. The optical band gap decreases from 2.72 to 2.62 eV as the Ni concentration increases from 1% to 4%. Current-voltage (I-V) measurements revealed enhanced electrical conductivity, which further increased under illumination, confirming the photoconducting nature of the films. These results demonstrate that Ni doping effectively tunes the properties of Cd1-xMnxS thin films, highlighting their potential as efficient window layer materials for thin-film solar cells and related optoelectronic devices.

cond-mat.mtrl-sci↗

arXiv2026

Interface controlled spin filtering and nonreciprocal transport in Altermagnet/Ising superconductor junctions

We investigate theoretically spin-resolved transport, spin filtering, and nonreciprocal effects in an Altermagnet/Ising superconductor (AM/ISC) junction with a spin-active interface. Using a modified Bogoliubov-de Gennes framework within the scattering formalism, we demonstrate that the interplay among intrinsic spin-orbit coupling (ISOC), anisotropic AM spin texture and spin-dependent interfacial scattering gives rise to strongly anisotropic charge and spin conductance. In the weak spin-mixing regime, transport remains predominantly helicity conserving and exhibits pronounced angular dependence governed by the relative orientation between the AM spin texture and interface magnetization. Increasing ISOC enhances spin conductance and leads to spin-selective Andreev reflection resulting in finite spin filtering. In contrast, the strong spin-mixing regime exhibits enhanced angular anisotropy and robust spin-polarized transport over a broad energy range. Conventional Andreev reflection becomes strongly suppressed, accompanied by substantial spectral redistribution. We further show that nonreciprocal transport persists throughout the single-band, intermediate and double-band ISC regime. The spin polarization and spin-filter efficiency exhibit nonmonotonic dependence on system parameters, reaching values up to $\sim 86\%$, with characteristic angular modulation determined by the AM spin texture. Finite-energy analysis reveals enhanced spin selectivity at low energies and suppression near the superconducting gap. Furthermore, strong spin mixing at the AM/ISC junction produces asymmetric conductance patterns, indicating nonreciprocal transport. Our results establish AM/ISC junctions as a versatile platform for tunable superconducting spintronics and directional spin transport.

cond-mat.supr-con↗

arXiv2025

Field free Josephson diode effect in Ising Superconductor/Altermagnet Josephson junction

Altermagnets (AMs) are an exotic class of antiferromagnet that exhibit spin-splitting even at the absence of net global magnetization and spin-orbit coupling (SOC) effects. In this work, we investigated theoretically, the supercurrent nonreciprocity in an Ising Superconductor/Altermagnet/Ising Superconductor (ISC/AM/ISC) Josephson junction which revealed asymmetric Josephson critical currents, $0 - π$ transitions and anomalous current-phase relationship (CPR). A strong Josephson diode efficiency (JDE) is observed due to the combined effects of AM strength and orientations in a conventional SC even in absence of SOC. However, it significantly enhances in presence of intrinsic SOC (ISOC), resulting in pronounced diode effect in both single and double band ISC/AM based Josephson junction. Additionally, it is observed that JDE is more prominent at higher AM strengths with intermediate orientations in all scenario. Notably, it is significantly suppressed for orientations $0^\circ$ and $45^\circ$. Our results also indicate that barrier transparency and AM lengths play a crucial role in optimizing the JDE. In a single-band ISC/AM system JDE persists for any AM length, while reduces at longer AM junction in case of a double-band ISC/AM system. Moreover, our results suggest that a diode efficiency of $\sim 52\%$ can be achieved in the proposed Josephson junction in both single and double band ISC/AM Josephson junction by considering strong AM strength. Furthermore, single band ISC offers wide AM orientation range in contrast to double band ISC for better tunability and optimization of JDE. Our findings highlight the impact of AM strength, orientation and ISOC on the JDE efficiency offering insights for superconducting diode design.

cond-mat.supr-con↗