arXiv subjects

Kritika Vijay

Publications and source records attributed to Kritika Vijay.

3 recordsLinked to original sources

arXiv2025

Anomalous Lattice Effect Originated Metal-Insulator Transition in FeSe$_x$

We present a comprehensive investigation of the structural, electrical transport, and magnetic properties of FeSe$_{\it{x}}$ ($\it{x}$ = 1.14, 1.18, 1.23, 1.28, and 1.32) to unravel the mechanism of the metal-insulator transition observed in these systems. For this, we systematically evaluated the structural parameters of FeSe$_{\it{x}}$ as a function of Se concentration and temperature. We observe increased lattice constants and cell volume with increased Se concentration. On the other hand, the temperature-dependent XRD studies suggest unusual lattice change around the metal-insulator (MI) transition temperature of the respective compositions. This remarkable observation suggests that the anomalous lattice effect originates the MI transition in these systems. Additionally, our density of states (DOS) calculations on FeSe$_{1.14}$ qualitatively explain the MI transition, as the low-temperature (50 K) structure DOS suggests a metallic nature and the high-temperature (300 K) structure DOS shows a gap near the Fermi level.

cond-mat.str-el↗

arXiv2023

Ultrafast Carrier Relaxation and Second Harmonic Generation in a Higher-Fold Weyl Fermionic System PtAl

In topological materials, shielding of bulk and surface states by crystalline symmetries has provided hitherto unknown access to electronic states in condensed matter physics. Interestingly, photo-excited carriers relax on an ultrafast timescale, demonstrating large transient mobility that could be harnessed for the development of ultrafast optoelectronic devices. In addition, these devices are much more effective than topologically trivial systems because topological states are resilient to the corresponding symmetry-invariant perturbations. By using optical pump probe measurements, we systematically describe the relaxation dynamics of a topologically nontrivial chiral single crystal, PtAl. Based on the experimental data on transient reflectivity and electronic structures, it has been found that the carrier relaxation process involves both acoustic and optical phonons with oscillation frequencies of 0.06 and 2.94 THz, respectively, in picosecond time scale. PtAl with a space group of $P$$2_{1}$3 allows only one non-zero susceptibility element i.e. $d_{14}$, in second harmonic generation (SHG) with a large value of 468(1) pm/V, which is significantly higher than that observed in standard GaAs(111) and ZnTe(110) crystals. The intensity dependence of the SHG signal in PtAl reveals a non-perturbative origin. The present study on PtAl provides deeper insight into topological states which will be useful for ultrafast optoelectronic devices.

cond-mat.mes-hall↗

arXiv2022

Effect on the Electronic and Magnetic Properties of Antiferromagnetic Topological Insulator MnBi$_2$Te$_4$ with Sn Doping

We thoroughly investigate the effect of nonmagnetic Sn doping on the electronic and magnetic properties of antiferromagnetic topological insulator MnBi$_2$Te$_4$. We observe that Sn doping reduces the out-of-plane antiferromagnetic (AFM) interactions in MnBi$_2$Te$_4$ up to 68\% of Sn concentration and above the system is found to be paramagnetic. In this way, the anomalous Hall effect observed at a very high field of 7.8 T in MnBi$_2$Te$_4$ is reduced to 2 T with 68\% of Sn doping. Electrical transport measurements suggest that all compositions are metallic in nature, while the low-temperature resistivity is sensitive to the AFM ordering and to the doping-induced disorder. Hall effect study demonstrates that Sn actually dopes electrons into the system, thus, enhancing the electron carrier density almost by two orders at 68\% of Sn. In contrast, SnBi$_2$Te$_4$ is found to be a p-type system. Angle-resolved photoemission spectroscopy (ARPES) studies show that the topological properties are intact at least up to 55\% of Sn as the Dirac surface states are present in the valance band, but in SnBi$_2$Te$_4$ we are unable to detect the topological states due to heavy hole doping. Overall, Sn doping significantly affects the electronic and magnetic properties of MnBi$_2$Te$_4$.

cond-mat.mtrl-sci↗