arXiv subjects

Amiya Mondal

Publications and source records attributed to Amiya Mondal.

3 recordsLinked to original sources

arXiv2026

Electric field induced Berry curvature dipole in quasi-one-dimensional Bi$_4$I$_4$

The nonlinear Hall effect in time-reversal symmetric materials offers a powerful probe into quantum geometry. Here, we investigate the electric-field-tunable nonlinear Hall response in few-layer $\text{Bi}_4\text{I}_4$ using comprehensive first-principles calculations across both its $α$ and $β$ phases. Guided by symmetry analysis, we track the evolution of the Berry curvature dipole (BCD) tensor from the monolayer to the bilayer configuration under an out-of-plane electric field. While the monolayer features a highly rigid band structure and modest BCD tunability, the bilayer architecture exhibits substantial field-induced band modifications, including a progressive Rashba splitting and eventual gap closure in the $β$ phase. Crucially, this field-tunability allows substantial enhancement of the BCD magnitude relative to the monolayer counterpart. Our findings establish quasi-one-dimensional bismuth halogenides as a promising platform for engineering nonlinear Hall response.

cond-mat.mtrl-sci↗

arXiv2026

Observation of Non-linear hall effect in Polycrystalline magnetic multilayes

The Nonlinear Hall effect(NLHE) driven principally by the Berry curvature dipole has been established in non-centrosymmetric vander Waals crystals, topological semimetals, and moiré superlattices, but its extension to technologically mature heavy-metal/ferromagnet multilayer platforms remains largely unexplored. Here, we report the observation of a robust NLHE in polycrystalline magnetic multilayers, persisting from 2 K to room temperature. The second-harmonic transverse voltage is independent of both excitation frequency and applied out-of-plane magnetic field, while the vanishingly small third-harmonic response confirms that the observed signal is not dominated by a quantum-metric contribution and instead reflects a genuine second-order electronic response. A scaling analysis of the second-order Hall conductivity against the longitudinal conductivity identifies a dominant, conductivity-independent term establishing the intrinsic berry curvature dipole. Our theoretical analysis, supported by first-principles DFT calculations, further satisfies and corroborates the experimental results. These results establish sputter-deposited polycrystalline thin film as the first engineered magnetic multilayer platform for BCD-driven nonlinear Hall transport, extending the NLHE material landscape beyond van der Waals systems into scalable, industry-compatible thin-film spintronic architectures suitable for high frequency rectifications and nonlinear sensors.

cond-mat.mes-hall↗

arXiv2026

On the depth of the adjoint representations

Let $F$ be a non-archimedean local field of odd residual characteristic $p$. The depth of a smooth representation of ${\rm GL}_n(F)$ is an invariant of Local Langlands Correspondence (LLC). The analogous notion on the Galois side of LLC is known as the slope of a local Galois representation. The slope is well related to the Swan conductor for irreducible Galois representations, whereas its behavior is subtle for reducible Galois representations. In this article, we provide an explicit formula for the slope of the adjoint of a Carayol representation of the local Galois group.

math.RT↗