arXiv subjects

Himanshu Sheokand

Publications and source records attributed to Himanshu Sheokand.

5 recordsLinked to original sources

arXiv2026

Complex electronic topography and magnetotransport in an in-plane ferromagnetic kagome metal

The intricate interplay between flat bands, Dirac cones, and magnetism in kagome materials has recently attracted significant attention from materials scientists, particularly in compounds belonging to the RMn6Sn6 family (R = Sc, Y, rare earths), due to their inherent magnetic frustration. Here, we present a detailed investigation of the ferromagnetic (FM) kagome magnet ScMn6(Sn0.78Ga0.22)6 using angle-resolved photoemission spectroscopy (ARPES), magnetotransport measurements, and density functional theory (DFT) calculations. Our findings reveal a paramagnetic-to-FM transition at 375 K, with the in-plane direction serving as the easy magnetization axis. Notably, ARPES measurements reveal a Dirac cone near the Fermi energy, while the Hall resistivity exhibits a substantial contribution from the anomalous Hall effect. Additionally, we observe a flat band spanning a substantial portion of the Brillouin zone, arising from the destructive interference of wave functions in the Mn kagome lattice. Theoretical calculations reveal that the gap in the Dirac cone can be modulated by altering the orientation of the magnetic moment. An out-of-plane orientation produces a gap of approximately 15 meV, while an in-plane alignment leads to a gapless state, as corroborated by ARPES measurements. This comprehensive analysis provides valuable insights into the electronic structure of magnetic kagome materials and paves the way for exploring novel topological phases in this material class.

cond-mat.mtrl-sci↗

arXiv2026

Observation of the Optical Phonons in α-MnTe films

The altermagnetic materials have emerged as model systems for studying spin split electronic structures, yet controlled epitaxial growth on technologically relevant substrates remains challenging. Among the known candidates, MnTe stands out as a prominent altermagnetic material owing to its layered structure and high Neel temperature. Here, we report the molecular beam epitaxy (MBE) growth of high quality alpha MnTe thin films on GaAs(111)B substrates and provide a comprehensive analysis of the growth evolution and structural properties. Raman spectroscopy reveals multiple vibrational features of alpha MnTe including modes near 121, and 140 1/cm. Combined with first principles phonon calculations, these features are identified as the Raman-active phonons of the hexagonal NiAs type lattice. Our results show that the high crystalline quality of MBE grown alpha MnTe enables the complete experimental resolution of all symmetry allowed Raman active phonon modes, highlighting epitaxial alpha MnTe as a robust thin film platform for investigating altermagnetism and its lattice coupled excitations.

cond-mat.mes-hall↗

arXiv2025

Topological character of the antiferromagnetic EuMg$_{2}$Bi$_{2}$

Antiferromagnetic EuM$_{2}$Pn$_{2}$ compounds, where M is a metal element and Pn is a pnictogen element, have been recognized as candidates for realizing a topologically nontrivial electronic structure. In this paper, we focus on EuMg$_2$Bi$_2$, whose topological nature still remains unclear. We present a comprehensive study based on several experimental and theoretical techniques. Magnetic susceptibility, electrical resistivity, and specific heat capacity measurements confirm the existence of an antiferromagnetic ordering. The electronic band structure was investigated by high-resolution angle-resolved photoemission spectroscopy (ARPES), supported by ab initio calculations. ARPES measurement reveals that the electronic structure of this system is dominated by linearly dispersive hole-like bands near the Fermi level. Theoretical analyses of the electronic band structure indicates that EuMg$_2$Bi$_2$ is a strong topological insulator, which should be reflected in the presence of a metallic surface state. We also theoretically examine the magnetic-field-induced anomalous Hall conductivity, confirming previously reported observations.

cond-mat.mtrl-sci↗

arXiv2025

Observation of Altermagnetic Spin Splitting in an Intercalated Transition Metal Dichalcogenide

Altermagnetism is a novel magnetic phase combining characteristics of both antiferromagnetism and ferromagnetic ordering. Despite growing theoretical interest in altermagnetic materials, reports of experimentally verified high Neel temperature layered compounds are limited or remain to be firmly established. Here, we present an angle resolved photoemission spectroscopy (ARPES) and density functional theory (DFT) study of Co1/4TaSe2, a compound we identify as a layered altermagnetic material. Magnetic susceptibility measurements confirm type A antiferromagnetic ordering with a Neel temperature of 178 K. Our ARPES measurements reveal an electronic band structure in excellent agreement with DFT calculations, demonstrating clear signatures of altermagnetic spin splitting at the Fermi surface. Furthermore, temperature dependent ARPES reveals a reconstructed valence band structure, with observable band shifts and the closing of energy gaps upon heating above the Neel temperature (TN), consistent with the suppression of altermagnetic order. These findings establish Co1/4TaSe2 as a promising platform for exploring altermagnetic phenomena.

cond-mat.mes-hall↗

arXiv2025

Electronic structure of a layered altermagnetic compound CoNb4Se8

Recently, there has been a growing interest in altermagnetism, a novel form of magnetism, characterized by unique spin-splitting even in the absence of both net magnetic moments and spin-orbit coupling. Despite numerous theoretical predictions, experimental evidence of such spin-splitting in real materials remains limited. In this study, we use angle-resolved photoemission spectroscopy (ARPES) combined with density functional theory (DFT) calculations to investigate the electronic band structure of the altermagnet candidate CoNb4Se8. This material features an ordered sublattice of intercalated Co atoms within NbSe2 layers. Magnetization and electrical resistivity measurements reveal the onset of antiferromagnetism below 168 K. Temperature dependent ARPES data, supported by DFT calculations, uncover spin split bands along the MGM high-symmetry direction. The observation of spin splitting in this high temperature altermagnet opens new avenues for exploring its electronic properties and potential applications in spintronic technologies.

cond-mat.mes-hall↗