arXiv subjects

Varun Shah

Publications and source records attributed to Varun Shah.

5 recordsLinked to original sources

arXiv2026

Strain Tuning of Orbital-Driven Giant Magnetoresistance in van der Waals ferrimagnet Mn$_3$Si$_2$Te$_6$

Strain engineering of magnetotransport offers a powerful strategy for uncovering emergent electronic and domain phenomena in quantum magnetic materials, while providing a promising pathway toward next-generation mechanically programmable spintronic technologies. Van der Waals magnets are particularly attractive in this context because their high crystallinity and mechanical flexibility allow exceptionally large, precisely controllable strain, enabling access to strain-induced functionalities unattainable in conventional solids. Here, we report systematic strain control of the van der Waals magnet Mn$_3$Si$_2$Te$_6$, which exhibits an unconventional colossal magnetoresistance whose microscopic origin remains under debate. We demonstrate in situ large-strain modulation of the electrical resistance in bulk crystals and show that the effect can be consistently explained by strain-tunable chiral orbital-current domains. Furthermore, measurements on exfoliated flake devices containing a single chiral domain reveal direct strain control of the electronic structure affected by orbital magnetic moment, establishing a unified microscopic mechanism for the unconventional colossal magnetoresistance. These results identify strain as an exceptionally effective control parameter for tailoring electronic and magnetic states in van der Waals magnets and provide a conceptual framework for realizing spin-straintronic functionalities based on orbital degrees of freedom.

cond-mat.mtrl-sci↗

arXiv2026

Large Independent Sets in Flag Spheres

For every $d \geq 4$, we construct a family of $(d-1)$-dimensional flag simplicial spheres $\mathcal K_n$ whose graphs contain independent sets of size asymptotically equal to the number of vertices. More precisely, we prove that for sufficiently large $n$, $$ \alpha(G(\mathcal K_n)) \geq f_0(\mathcal K_n) - \frac{C\,f_0(\mathcal K_n)}{\left(\log f_0(\mathcal K_n)\right)^{\lfloor d/2 \rfloor-1}},$$ where $C = C(d) > 0$. This disproves a recent conjecture of Chudnovsky and Nevo.

math.CO↗

arXiv2025

Magnetic resonance and microwave resistance modulation in van der Waals colossal-magnetoresistance material

Colossal magnetoresistance (CMR) is a fascinating quantum phenomenon that continues to draw significant interest in condensed matter physics. Mn3Si2Te6 has emerged as a prototypical CMR material, notable for its puzzling magnetoresistance behavior and pronounced directional anisotropy. Despite extensive research, the mechanisms driving CMR in Mn3Si2Te6 remain elusive [1-4]. In this work, we explore the magnetic resonance of Mn3Si2Te6 and observe a reduced g-factor for magnetic fields applied along the crystalline c-axis compared to the ab-plane, indicating a substantial orbital magnetization contribution along the c-axis. Furthermore, we detect resistance modulation under resonance conditions, suggesting that CMR in Mn3Si2Te6 is sensitive to the out-of-the plane spin polarization. These findings shed new light on the role of orbital magnetic moment in Mn3Si2Te6, offering a deeper understanding of the interplay between spin, orbital and lattice degrees of freedom of electrons in this system.

cond-mat.mtrl-sci↗

arXiv2024

The Divisibility of $\mathrm{GL}(n, q)$ Character Values

Let $q$ be a prime power, and $d$ a positive integer. We study the proportion of irreducible characters of $\mathrm{GL}(n,q)$ whose values evaluated on a fixed matrix $g$ are divisible by $d$. As $n$ approaches infinity, this proportion tends to $1$ when $q$ is coprime to $d$. When $q$ and $d$ are not coprime, and $g=1$, this proportion is bounded above by $\frac{1}{q}$.

math.RT↗

arXiv2023

On the Divisibility of Degrees of Representations of Lie Algebras

Let $\mathfrak g$ be a reductive Lie algebra, and $m$ a positive integer. There is a natural density of irreducible representations of $\mathfrak g$, whose degrees are not divisible by $m$. For $\mathfrak g=\mathfrak{gl}_n$, this density decays exponentially to $0$ as $n \to \infty$. Similar results hold for simple Lie algebras and Lie groups, and there are versions for self-dual and orthogonal representations.

math.RT↗