arXiv subjects

Amit Vashist

Publications and source records attributed to Amit Vashist.

8 recordsLinked to original sources

arXiv2026

Observation of linear magnetoresistance and planar Hall effect in the Dirac semimetal PdTe

PdTe is a Dirac semimetal that also exhibits superconductivity, providing an intriguing platform to explore topological superconductivity and unconventional magnetotransport phenomena. While the superconducting properties of PdTe have been extensively studied in recent years, the detailed magnetotransport phenomena have remained unexplored. Here, we present the first observation of linear magnetoresistance (LMR) and the planar Hall effect (PHE) in a high-quality single crystal of PdTe. We observe temperature-dependent unsaturated LMR in both in-plane ($B \parallel I$) and out-of-plane ($B \perp I$) configurations. The magnetoresistance (MR) shows a crossover from parabolic to linear dependence at the critical field Bc, and detailed analysis indicates that disorder-driven mobility fluctuations are the origin rather than the Abrikosov quantum-limit mechanism. Furthermore, prominent PHE has been observed by rotating the magnetic field within the plane of the sample. The detailed analysis of the field and temperature dependence of PHE-amplitude, along with the parametric plot, suggests that PHE originates predominantly from the anisotropic orbital magnetoresistance rather than the chiral anomaly. Our results demonstrate that although the Dirac point is close to the Fermi level, the observed LMR and PHE in the Dirac semimetal PdTe can be understood within a semiclassical transport framework, highlighting the importance of distinguishing between topological and conventional classical transport mechanisms in topological materials

cond-mat.mes-hall↗

arXiv2025

Exploring unconventional superconductivity in PdTe via Point Contact Spectroscopy

Palladium Telluride (PdTe), a non-layered intermetallic crystalline compound, has captured attention for its unique superconducting properties and strong spin-orbit coupling. In this work, we investigate the superconducting state of PdTe using point-contact Andreev reflection (PCAR) spectroscopy. The experimental data are analyzed using the Blonder-Tinkham-Klapwijk (BTK) model for s, p and d wave symmetries. Our results reveal clear evidence of unconventional superconductivity. The superconducting gap showing features consistent with either p-wave or d-wave pairing symmetries but cannot be fitted with s-wave symmetry. The observed anisotropic gap structure and deviations from conventional BCS behaviour highlight the complex nature of the pairing interactions in PdTe. These findings provide strong evidence of unconventional pairing symmetry in this material.

cond-mat.supr-con↗

arXiv2024

A quantized anomalous Hall effect above 4.2 K in stacked topological insulator/magnet bilayers

Quantized anomalous Hall effects (QAHEs) occur in remarkable electronic states which possess not only quantized Hall signals but in some cases regions of dissipationless electron transport. The initial demonstrations of a QAHE in a magnetically-doped topological insulator (TI) required temperatures below 100 mK, and since then a major focus of the field has been to increase the temperature scale. Here, we report quantized Hall signals up to 10 K (in what is known as the parity anomaly state) in TI/magnet bilayers made by mechanical assembly, rather than by conventional deposition techniques. This is a factor of 100 higher temperature than any previous realization of a QAHE in a proximity-coupled TI/magnet heterostructure made by deposition, and approximately twice the previous record for any QAHE system.

cond-mat.mes-hall↗

arXiv2024

Multigap superconductivity with non-trivial topology in a Dirac semimetal PdTe

Recently, PdTe has been identified as a Dirac semimetal with potential for unconventional superconductivity based on ARPES measurements. This study presents electrical transport and magnetization measurements conducted on high-quality single crystals of PdTe. Anisotropy in the upper critical magnetic field is observed in resistivity versus temperature data measured under various applied magnetic fields for in-plane (B II ab ) and out-of-plane (B II c) orientations. The magnetic field versus temperature (H - T) phase diagram extracted from resistivity data exhibits an upward curvature akin to several multigap superconductors. Additionally, magnetization measurements reveal de Haas-Van Alphen (dHvA) oscillations in both B II ab and B II c orientations. Fourier analysis of the quantum oscillations identifies two Fermi pockets. Moreover, the Landau fan diagram for a small Fermi pocket confirms a non-trivial Berry phase π, indicative of the Dirac nature of PdTe. Based on quantum oscillation data, a plausible band diagram is constructed.

cond-mat.supr-con↗

arXiv2022

Nanomechanical Characterization of an Antiferromagnetic Topological Insulator

The antiferromagnetic topological insulator MnBi2Te4 (MBT) exhibits an ideal platform to study exotic topological phenomena and magnetic properties. The transport signatures of magnetic phase transitions in the MBT family materials have been well-studied. However, their mechanical properties and magneto-mechanical coupling have not been well-explored. We use nanoelectromechanical systems to study the intrinsic magnetism in MBT thin flakes via their magnetostrictive coupling. We investigate mechanical resonance signatures of magnetic phase transitions from antiferromagnetic (AFM) to canted antiferromagnetic (cAFM) to ferromagnetic (FM) phases versus magnetic field at different temperatures. The spin-flop transitions in MBT are revealed by frequency shifts of mechanical resonance. With temperatures going above TN, the transitions disappear in the resonance frequency map, consistent with transport measurements. We use a magnetostrictive model to correlate the frequency shifts with the spin-canting states. Our work demonstrates a technique to study magnetic phase transitions, magnetization and magnetoelastic properties of the magnetic topological insulator.

cond-mat.mes-hall↗

arXiv2022

Gate-tunable anomalous Hall effect in a 3D topological insulator/2D magnet van der Waals heterostructure

We demonstrate advantages of samples made by mechanical stacking of exfoliated van der Waals materials for controlling the topological surface state of a 3-dimensional topological insulator (TI) via interaction with an adjacent magnet layer. We assemble bilayers with pristine interfaces using exfoliated flakes of the TI BiSbTeSe2 and the magnet Cr2Ge2Te6, thereby avoiding problems caused by interdiffusion that can affect interfaces made by top-down deposition methods. The samples exhibit an anomalous Hall effect (AHE) with abrupt hysteretic switching. For the first time in samples composed of a TI and a separate ferromagnetic layer, we demonstrate that the amplitude of the AHE can be tuned via gate voltage with a strong peak near the Dirac point. This is the signature expected for the AHE due to Berry curvature associated with an exchange gap induced by interaction between the topological surface state and an out-of-plane-oriented magnet.

cond-mat.mes-hall↗

arXiv2019

Fermi surface topology and large magnetoresistance in the topological semimetal candidate PrBi

We report a detailed magnetotransport study on single crystals of PrBi. The presence of $f$-electrons in this material raises the prospect of realizing a strongly correlated version of topological semimetals. PrBi shows a magnetic field induced metal insulator transition below $T \sim 20$ K and a very large magnetoresistance ($\approx 4.4 \times 10^4~$) at low temperatures ($T= 2$ K). We have also probed the Fermi surface topology by de Haas van Alphen (dHvA) and Shubnikov de Haas (SdH) quantum oscillation measurements complimented with density functional theory (DFT) calculations of the band structure and the Fermi surface. Angle dependence of the SdH oscillations have been carried out to probe the possible signature of surface Dirac fermions. We find three frequencies corresponding to one electron ($α$) and two hole ($β$ and $γ$) pockets in experiments, consistent with DFT calculations. The angular dependence of these frequencies is not consistent with a two dimensional Fermi surface suggesting that the transport is dominated by bulk bands. Although the transport properties of this material originate from the bulk bands, the high mobility and small effective mass are comparable to other compounds in this series proposed as topologically nontrivial.

cond-mat.str-el↗

arXiv2018

Observation of planar Hall effect in Type-II Dirac semimetal PtTe$_{2}$

We report experimental observation of the Planar Hall effect (PHE) in a type-II Dirac semimetal PtTe$_2$. This unusual Hall effect is not expected in nonmagnetc materials such as PtTe$_2$, and has been observed previously mostly in magnetic semiconductors or metals. Remarkably, the PHE in PtTe$_2$ can be observed up to temperatures near room temperature which indicates the robustness of the effect. This is in contrast to the chiral anomaly induced negative longitudnal magnetoresistance (LMR), which can be observed only in the low temperature regime and is sensitive to extrinsic effects, such as current jetting and chemical inhomogeneities in crystals of high mobility. Planar Hall effect on the other hand is a purely intrinsic effect generated by the Berry curvature in Weyl semimetals. Additionally, the PHE is observed for PtTe$_2$ even though the Dirac node is $\approx 0.8$~eV away from the Fermi level. Thus our results strongly indicate that PHE can be used as a crucial transport diagnostic for topological character even for band structures with Dirac nodes slightly away from the Fermi energy.

cond-mat.mes-hall↗