S Bhattacharya | Searcharxiv

arXiv2025

Weak decays of Bc meson in a QCD potential model

The leptonic and semileptonic decay propertis of Bc mesons are studied in a QCD potential model. The CKM element for the leptonic decay is calculated by evaluating its decay constant. With the help of the Isgur-Wise function, the form factors and the CKM element for semileptonic decay are also calculated. The variation in four-momentum square in the two decays demands two different scales of the strong coupling constant \alpha_s. Thus, a two-scale picture is evident from the study. We compute the decay constant f_p for leptonic decay and form factors for semileptonic decay with two different \alpbda scales in a specific prescription where it is related to the strong coupling \alpha_s. Within the potential model, we find the scale for leptonic decay is \lambda \le 0.150 GeV and for semileptonic decay is \lamda \ge 0.410 GeV.

hep-ph↗

arXiv2022

Rashba and Dresselhaus effects in doped methylammonium lead halide perovskite MAPbI$_3$

Inorganic-organic lead halide perovskites, particularly methylammonium lead halide (MAPbI$_3$) perovskite, is perceived to be a promising material for optoelectronics and spintronics. However, lead toxicity and instability under air and moisture restrict its practical uses. Hence, it is essential to reduce lead extent by substituting appropriate alternatives. Here, we substitute Sn and Ge in cubic MAPbI$_3$ and compare various properties of hybrid perovskites by employing state-of-the-art first-principles-based methodologies, viz., density functional theory (DFT) with semilocal and hybrid functional (HSE06) and generalized gradient approximation (PBE) combined with spin-orbit coupling (SOC). We mainly study the Rashba-Dresselhaus (RD) effect, which occurs here due to two major mechanisms breaking inversion symmetry, i.e., static and dynamic, and the presence of heavy elements contributing to significant SOC. We find non-negligible spin-splitting effects in the conduction band minimum (CBm) and valence band maximum (VBM) for hybrid perovskites. For a deeper understanding of the observed spin-splitting, the spin textures are analyzed and Rashba coefficients are calculated. We find that Dresselhaus effect comes into play in substituted hybrids in addition to the usual Rashba effect observed in pristine compound. We also observe that the strength of Rashba spin-splitting can be substantially tuned on application of uniaxial strain ($\pm5\%$). Also, we notice that some of the hybrids are mechanically stable and ductile. Hence these hybrid perovskites can prove to be potent for perovskite-based spintronic applications.

cond-mat.mtrl-sci↗

arXiv2010

Neutron-gamma discrimination by pulse analysis with superheated drop detector

Superheated drop detector (SDD) consisting of drops of superheated liquid of halocarbon is irradiated to neutrons and gamma-rays from 252Cf fission neutron source and 137Cs gamma source separately. The analysis of pulse height of the signals in the neutron and gamma-ray sensitive temperature provides strong information on the identification of neutron and gamma-ray induced events.

physics.ins-det↗