arXiv subjects

Sonika

Publications and source records attributed to Sonika.

5 recordsLinked to original sources

arXiv2025

New plasmon-like mode in PdTe$_{2}$: Raman scattering and memory function study

PdTe$_2$ is a type II Dirac semimetal that has garnered significant attention due to its intriguing electronic and topological properties. Here, we report temperature dependent Raman scattering study of PdTe$_2$ in the temperature range from 10 K to 300 K. Our study reveals emergence of a new unreported peak below 100 K, centered around 250 cm$^{-1}$. We argue that the new mode is not a phonon mode because the Raman spectra calculated using Density Functional Theory shows only two intense peaks at 85 $ cm^{-1}$ and 128 $cm^{-1}$. To ascertain the origin of this new peak, we constructed a microscopic model of electrons coupling to a single plasmon mode at 250 $cm^{-1}$ and using the memory function formalism, we obtained that the Raman relaxation rate is linear in frequency. We also performed phenomenological analysis of the Raman response from the experimental data and computed frequency dependent Raman relaxation rate, which is also found to exhibit a linear dependence on frequency. With the congruence of our theoretical and phenomenological results we could ascertain that the new mode observed at low temperatures is indeed a plasmon-like mode. Further, phonon frequencies and line widths of the two phonon modes exhibit anomalous behavior above 100 K.

cond-mat.str-el↗

arXiv2024

Magnetotransport and thermoelectric studies of antiperovskite semimetal: Mn3SnC

We explore the magnetotransport and thermoelectric (Seebeck and Nernst coefficients) properties of Mn3SnC an antiperovskite magnetic Nodal line semimetal. Mn3SnC shows paramagnetic (PM) to concurrent antiferromagnetic (AFM)/ferromagnetic (FM) transition at 286 K. The electrical resistivity and Seebeck coefficient indicate the importance of electron magnon scattering in the concurrent AFM/FM regime. We observed a large positive magnetoresistance (MR) of 8.2 at 8 T field near magnetic transition, in the otherwise negative MR behaviour for low temperatures. The electrical resistivity and MR show a weak thermal hysteresis around the boundary of transition temperature and the width of hysteresis decreases as magnetic field increases. Interestingly the Hall and Seebeck coefficients change sign from positive to negative below the transition temperature, highlighting the different scattering for holes and electrons in this multi-band system. The Seebeck and Nernst signal exhibit two sharp anomalies; one at the transition temperature and another at 50 K. The anomaly at magnetic transition in the Nernst signal disappear at 8 T magnetic field, owing to the reduction of magnetic fluctuation. A pseudo-gap near the Fermi level produces an upturn with a broad minimum in the Seebeck signal.

cond-mat.str-el↗

arXiv2024

Extended Kohler's scaling, a low temperature anomaly and Isosbestic point in the charge density wave state of 1T-VSe$_2$

1T-VSe$_2$ is a narrow band transition metal chalcogenide that shows charge density wave (CDW) state below $T_{CDW}$ = 110 K. Here, we have explored the relevance of Kohler's rule and the thermal transport properties of VSe$_2$ across the CDW state. The magnetoresistance (MR) follows Kohler's rule above $T_{CDW}$, while an extended Kohler's rule is employed below $T_{CDW}$. Interestingly, we observed an anomaly in MR at T = 20 K, below which MR value decreases on lowering temperature. This anomaly is also reflected in the slope ($\kappa$) of Kohler's plots and the relative change in the thermal excitation induced carrier density ($n_T$) also. The $T_{CDW}$ remains largely unaffected in both electrical resistivity ($\rho(T)$) and longitudinal Seebeck coefficient ($\it{S_{xx}}$) even under a strong magnetic field of 14 Tesla. However, the application of magnetic field enhances the peak intensity of $\it{S_{xx}}$ at T $\sim$ 60 K. Additionally, $\it{S_{xx}(T)}$ curves measured at different fields exhibit a crossover at T = 20 K, which suggest the existence of unique feature in the CDW state of VSe$_2$ \textit{i.e.} a locally exact isosbestic point.

cond-mat.str-el↗

arXiv2023

Chiral anomaly and positive longitudinal magnetoresistance in the type-II Dirac semimetals $\it{A}_x$PdTe$_2$ (\textit{A} = Cu, Ag)

The Planar Hall effect (PHE) in topological materials has been a subject of great interest in recent years. Generally, it is understood to originate from the chiral-anomaly (CA) induced charge pumping between doubly degenerate Weyl nodes. However, the occurrence of PHE in the materials with positive and anisotropic orbital magnetoresistance has raised questions about CA being the sole origin of this effect. Here, we report the PHE, magnetoresistance, and thermal transport properties (Seebeck and Nernst coefficients) on the Ag intercalated PdTe$_2$. We observe positive longitudinal magnetoresistance, the linear field dependence of the amplitude of PHE, and a prolate pattern in the parametric plots. The planar Hall resistivity and anisotropic magnetoresitance fits well with theoretical study of CA being the origin of PHE. So, our observations are consistent with Weyl physics dominating the PHE in PdTe$_2$, Cu$_{0.05}$PdTe$_2$, and Ag$_{0.05}$PdTe$_2$. We further support our data with a theoretical model that reproduces the qualitative experimental features. In addition, we have calculated the Seebeck ($\it{S}$) and Nernst ($\nu$) coefficients for PdTe$_2$ and Cu and Ag intercalated compounds. The estimated values of Fermi energy for the Cu and Ag intercalated compounds are respectively two times and three times larger than that of PdTe$_2$.

cond-mat.str-el↗

arXiv2021

Planar Hall effect in Cu intercalated PdTe$_2$

We present the Planar Hall effect studies on the Cu intercalated type-II Dirac semimetal PdTe$_{2}$. The electrical resistivity exhibits a positive field dependence both in perpendicular and parallel field directions, causing non-zero anisotropy. The longitudinal magnetoresistance shows almost linear field dependence at low temperatures. A tilted prolate spheroid shaped orbits are observed in parametric plot between transverse and longitudinal resistivities. Our study suggest that for the type-II Dirac semimetal materials with positive longitudinal magnetoresistance, the origin of Planar Hall effect cannot be asserted with certainty to the topological or non-topological without taking into account the anisotropy of Fermi surface.

cond-mat.str-el↗