arXiv subjects

Shivam Yadav

Publications and source records attributed to Shivam Yadav.

7 recordsLinked to original sources

arXiv2026

Magneto-transport signatures in periodically-driven Weyl and multi-Weyl semimetals

We investigate the influence of a time-periodic driving (for example, by shining circularly polarized light) on three-dimensional Weyl and multi-Weyl semimetals, in the planar Hall and planar thermal Hall set-ups. We incorporate the effects of the drive by using the Floquet formalism in the large frequency limit. We evaluate the longitudinal magneto conductivity, planar Hall conductivity, longitudinal thermo-electric coefficient, and transverse thermo-electric coefficient, using the semi-classical Boltzmann transport equations. We demonstrate the explicit expressions of these transport coefficients in certain limits of the parameters, where it is possible to perform the integrals analytically. We cross-check our analytical approximations by comparing the physical values with the numerical results, obtained directly from the numerical integration of the integrals. The answers obtained show that the topological charges of the corresponding semimetals have profound signatures in these transport properties, which can be observed in experiments.

cond-mat.mes-hall↗

arXiv2026

Topological properties of spin block magnetic ladders in proximity of a superconductor: application to BaFe$_{2}$S$_{3}$

Monoatomic chains with magnetic order in proximity of a s-wave superconductor can host Majorana edge modes. In this paper, we extend this idea to more complex spin-block chains such as the BaFe$_{2}$S$_{3}$ magnetic material that has a spin-ladder like structure. We investigate the topological phase diagram of such a system as function of the system parameters. We show that the coupling between chains within the ladder leads to the topological phase with a winding number larger than the sum of two single magnetic chains. Furthermore, strong coupling between chains leads to fractal-like substructure in the topological phase diagram. By investigating the real space properties of such a system and particularly its edge modes, we find that the system spectrum contains several in-gap states that we analyze in detail.

cond-mat.supr-con↗

arXiv2025

BoxingVI: A Multi-Modal Benchmark for Boxing Action Recognition and Localization

Accurate analysis of combat sports using computer vision has gained traction in recent years, yet the development of robust datasets remains a major bottleneck due to the dynamic, unstructured nature of actions and variations in recording environments. In this work, we present a comprehensive, well-annotated video dataset tailored for punch detection and classification in boxing. The dataset comprises 6,915 high-quality punch clips categorized into six distinct punch types, extracted from 20 publicly available YouTube sparring sessions and involving 18 different athletes. Each clip is manually segmented and labeled to ensure precise temporal boundaries and class consistency, capturing a wide range of motion styles, camera angles, and athlete physiques. This dataset is specifically curated to support research in real-time vision-based action recognition, especially in low-resource and unconstrained environments. By providing a rich benchmark with diverse punch examples, this contribution aims to accelerate progress in movement analysis, automated coaching, and performance assessment within boxing and related domains.

cs.CV↗

arXiv2025

Landau levels in Weyl semimetal under uniaxial strain

The external strain can lead to the similar effect to the external applied magnetic field. Such pseudomagnetic field can be larger than typical magnetic fields, what gives the opportunity to experimentally study the Landau levels. In this paper we study the effects of uniaxial strain on the Weyl nodes, using continuum and lattice model. In the continuum model we show that the uniaxial strain leads to magnetic field renormalization, which in practice corresponds to the shift of the Landau levels to higher energy. We also investigate type-I and type-II Weyl nodes using lattice model. In this case, the magnetic field is introduced by the Pierels substitution, while uniaxial strain by the direction dependence of hopping integrals. This allowed us to probe the Landau level and system spectrum which takes form of Hofstadter butterfly. We show that the renormalization of magnetic field, similar to this observed in the continuum model, emerges.

cond-mat.mes-hall↗

arXiv2025

Low temperature phase of AuSn$_{4}$ induced by the van der Waals interactions

AuSn$_{4}$ is the example of an compound that exhibits topological properties. Recent XRD measurements reveal an ambiguous nature of the crystal structure, as it can be realized with either Aea2 or Ccca symmetry. Motivated by this, we analyze the dynamical stability of the compound. We discuss the role of van der Waals (vdW) corrections within the ab initio calculation. Interestingly, our main result indicates that AuSn$_{4}$ can be unstable with both Aea2 and Ccca symmetries, due to the soft modes in the phonon spectra. From the soft mode analyses we find dynamically stable Pc structure. This structure has always smaller energy than Aea2 or Ccca crystal and it stays independent of the vdW correction. We also show that the comparison of theoretical electronic properties with the experimental ARPES measurements. Our findings may be valuable in the future investigations of AuSn$_{4}$-like compounds.

cond-mat.mtrl-sci↗

arXiv2023

Ecological system with fear induced group defence and prey refuge

In this study, we investigate the dynamics of a spatial and non spatial prey-predator interaction model that includes the following: (i) fear effect incorporated in prey birth rate; (ii) group defence of prey against predators; and (iii) prey refuge. We provide comprehensive mathematical analysis of extinction and persistence scenarios for both prey and predator species. To better explore the dynamics of the system, a thorough investigation of bifurcation analysis has been performed using fear level, prey birth rate, and prey death rate caused by intra-prey competition as bifurcation parameter. All potential occurrences of bi-stability dynamics have also been investigated for some relevant sets of parametric values. Our numerical evaluations show that high levels of fear can stabilize the prey-predator system by ruling out the possibility of periodic solutions. Also, our model Hopf bifurcation is subcritical in contrast to traditional prey-predator models, which ignore the cost of fear and have supercritical Hopf bifurcations in general. In contrast to the general trend, predator species go extinct at higher values of prey birth rates. We have also found that, contrary to the typical tendency for prey species to go extinct, both prey and predator populations may coexist in the system as intra-prey competition level grows noticeably. The stability and Turing instability of associated spatial model have also been investigated analytically. We also perform the numerical simulation to observe the effect of different parameters on the density distribution of species. Different types of spatiotemporal patterns like spot, mixture of spots and stripes have been observed via variation of time evolution, diffusion coefficient of predator population, level of fear factor and prey refuge. The fear level parameter (k) has a great impact on the spatial dynamics of model system.

q-bio.PE↗

arXiv2023

Magneto-optical conductivity in the type-I and type-II phases of Weyl/multi-Weyl semimetals

Magneto-optical conductivity is a very widely studied transport coefficient, useful to understand and characterize the behaviour of materials under magnetic fields. Using the Kubo formula, we compute the components of the conductivity tensor $σ_{μν}$ transverse to a uniform magnetic field $\mathbf B$, for a single node of a multi-Weyl semimetal (with monopole charge $J$ equal to two or three). We also include the results for a Weyl semimetal (with $J=1$), and identify peaks in the conductivity profile which were not reported in earlier studies. In our analysis, we explore how the tilting of the Weyl/multi-Weyl cone affects $σ_{μν}$, focussing on both type-I and type-II phases. All these systems have a linear-in-momentum dispersion along the tilting axis, which is chosen to align with $\mathbf B$. In the type-II phases, open Fermi pockets appear as artifacts of the low-energy effective continuum models, which ignore higher-order momentum terms of the actual bandstructures. Hence, we supplement the linear power term with a cubic term, which closes the Fermi pockets, thus eliminating any need for an ad hoc cutoff for the momentum integrals. Our results reveal that the absorptive parts of $σ_{μν}$ display multiple peaks as functions of the frequency, whose locations are determined by an energy scale $\sim |\mathbf B|^{J/2} $.

cond-mat.mes-hall↗