arXiv subjects

Syeda Neha Zaidi

Publications and source records attributed to Syeda Neha Zaidi.

3 recordsLinked to original sources

arXiv2026

Fractional Impurity Entropy from Potential Scattering in a Free Electron Gas

Fractional changes in entropy are often associated with strong electron correlations or non-Abelian anyons in topological systems. We show that neither condition is necessary -- a system of free electrons on a ring scattering off a repulsive point-like impurity undergoes a $k_B\ln\sqrt 2$ entropy change as the impurity strength is increased. This effect arises from a shift of allowed single-particle momenta from integer quantization to half-integer quantization, induced by the impurity. We show that this fractional entropy change is universal across a broad class of single-particle dispersions, demonstrating that such signatures can arise without strong correlations or topological order.

cond-mat.mes-hall↗

arXiv2025

Wiedemann-Franz violation and thermal Hall effect in kagome metal TbCr6Ge6

The thermal Hall effect has emerged as a powerful probe of exotic excitations in correlated quantum materials, providing access to charge-neutral heat carriers that remain invisible to electrical transport. To directly examine how heat and charge respond in relation within a kagome metal, we investigate the ferrimagnetic rare-earth 1-6-6 compound TbCr6Ge6 using the Wiedemann-Franz (WF) framework. We observe a dramatic breakdown of the WF law across the ferrimagnetic transition, where both longitudinal and transverse Lorenz ratios, L_{xx,xy} = κ_{xx,xy} / (T σ_{xx,xy}), deviate strongly from the Sommerfeld value L_0. After a partial recovery toward L_0 near 5-7 K, the Lorenz ratios are sharply suppressed well below L_0 despite a metallic charge response. We further find a pronounced low-temperature suppression of both L_{xx} and L_{xy} and a sign-changing transverse Lorenz ratio, indicating a clear decoupling between heat and charge transport and signaling substantial contributions from charge-neutral excitations whose Berry-curvature-driven transverse response evolves with temperature and magnetic field. TbCr6Ge6 thus provides a tunable metallic platform in which exchange-driven ferrimagnetism governs both longitudinal and transverse thermal responses, enabling controlled departures from Wiedemann-Franz behavior over an experimentally accessible temperature and field range.

cond-mat.str-el↗

arXiv2023

Continuous dynamical decoupling of spin chains: Inducing two-qubit interactions to generate perfect entanglement

Efficient control over entanglement in spin chains is useful for quantum information processing applications. In this paper, we propose the use of a combination of two different configurations of strong static and oscillating fields to control and generate near-perfect entanglement between any two spins in a spin chain, even in the presence of noise. This is made possible by the fact that our control fields not only decouple the spin chain from its environment but also selectively modify the spin-spin interactions. By suitably tuning these spin-spin interactions via the control fields, we show that the quantum state of any two spins in the spin chain can be made to be a Bell state. We illustrate our results for various spin chains, such as the XY model, the XYZ model, and the Ising spin chain.

quant-ph↗