arXiv subjects

A. Uzair

Publications and source records attributed to A. Uzair.

4 recordsLinked to original sources

arXiv2026

Topological magnetotransport in modified-Haldane systems

We present a theoretical study of quantum magneto-transport and magneto-optical (M-O) properties in modified-Haldane model; which is applicable to diverse classes of two-dimensional (2D) quantum materials such as buckled Xene monolayers and transition metal dichalcogenide (TMDC) monolayers. By varying the staggered sublattice potential and intrinsic spin-orbit coupling, we identify distinct topological regimes and analyze their manifestations in the emergence of Landau levels, the evolution of the density of states, and the characteristics of M-O absorption spectra. Using the Kubo formalism, we compute the longitudinal and Hall M-O conductivities and show that inter-Landau-level (inter-LL) transitions produce characteristic resonance features that provide optical signatures of the underlying topological phases. Within this framework, we demonstrate electrically tunable topological phase transitions in buckled silicene. Extending our study to monolayer TMDCs, we show that inspite of large band gap, the spin-valley coupling provides a powerful tool for tailoring M-O absorption features across wide range of 2D materials. Collectively, these results underscore modified-Haldane-model materials as an ideal testbed for engineering quantum transport, with promising applications in topological photonics, valleytronic devices, and next-generation optoelectronics.

cond-mat.mes-hall↗

arXiv2025

Polarization-dependent observables in $H\to \ell^{+}\ell^{-} γ$ in the SM

The rare three body decay of a Higgs boson to a lepton-anti lepton pair and a photon has begun to attract attention, after the first evidence for the $H\to Zγ$ at CMS and ATLAS, which is a sub process of $H \to \ell^+ \ell^- γ$ . To investigate some important features of this process, we suggest that the polarized forward-backward and the photon polarization asymmetries could be useful to probe its important properties, such as the behavior of Yukawa coupling, resonance, and non-resonance contributions. Our analysis introduces a comprehensive framework to evaluate the aforementioned polarization-dependent observables. By analyzing the polarization effects of the final-state photon and lepton separately on forward-backward asymmetries, we demonstrate that loop-induced contributions play a significant role to investigate these asymmetries. Unlike the unpolarized case, where the interference effects of resonance and non-resonance effects are minimal, we show that polarization dependent observables offer a powerful tool to analyze these features of this decay mode. Furthermore, these observables can provide a handy tool for probing possible signatures of physics beyond the SM.

hep-ph↗

arXiv2024

Analysis of final state lepton polarization-dependent observables in $H\to \ell^{+}\ell^{-} γ$ in the SM at loop level

Recently, the CMS and ATLAS collaborations have announced the results for $H\rightarrow Z[\rightarrow \ell^{+}\ell^{-}]γ$ with $\ell=e$ or $μ$ \cite{CMS:2022ahq,CMS:2023mku}, where $H\rightarrow Zγ$ is a sub-process of $H\rightarrow \ell^{+} \ell^{-} γ$. This semi-leptonic Higgs decay receives loop induced resonant $H\rightarrow Z[\rightarrow \ell^{+}\ell^{-}]γ$ as well as non-resonant contributions. % as discussed in \cite{Kachanovich:2021pvx}. To probe further features coming from these contributions to $H\rightarrow \ell^{+} \ell^{-} γ$, we argue that the polarization of the final state leptons is also an important parameter. We show that the contribution from the interference of resonant and non-resonant terms plays an important role when the polarization of final state lepton is taken into account, which is negligible in the case of unpolarized leptons. For this purpose, we have calculated the polarized decay rates and the longitudinal ($P_L$), normal ($P_N$) and transverse ($P_T$) polarization asymmetries. We find that these asymmetries purely come from the loop contributions and are helpful to further investigate the resonant and non-resonant nature of $H\rightarrow Z[\rightarrow \ell^{+}\ell^{-}]γ$ decay. We observe that for $\ell=e,μ$, the longitudinal decay rate is highly suppressed around $m_{\ell\ell}\approx 60$GeV when the final lepton spin is $-\frac{1}{2}$, dramatically increasing the corresponding lepton polarization asymmetries. Furthermore, we analyze another observable, the ratio of decay rates $R^{\ell\ell'}_{i\pm}$, where $\ell$ and $\ell'$ refer to different final state lepton generations. Precise measurements of these observables at the HL-LHC and the planned $e^{+}e^{-}$ can provide a fertile ground to test not only the SM but also to examine the signatures of possible NP beyond the SM.

hep-ph↗

arXiv2018

Collision-dominated conductance in clean 2D metals

We study the temperature-dependent corrections to the conductance due to electron-electron (e-e) interactions in clean two-dimensional conductors, such as lightly doped graphene or other Dirac matter. We use semiclassical Boltzmann kinetic theory to solve the problem of collision-dominated transport between reflection-free contacts. Time-reversal symmetry and the kinematic constraints of scattering in two dimensions (2D) ensure that inversion-odd and inversion-even distortions of the quasiparticle distribution relax with parametrically different rates at low temperature. This entails the surprising result that at lowest temperatures the conductance of very long samples tends to the noninteracting, ballistic conductance, despite the relaxation of the quasiparticle distribution to a drifting equilibrium. The relative correction to the conductance depends on the ratio of relaxation rates of even and odd modes and scales as delta G/G_{ballistic}~(T/E_F)[Log(E_F/T)]^{1/2}, in stark contrast to the behavior in other dimensionalities. This holds generally in 2D systems with simply connected and convex but otherwise arbitrary Fermi surfaces, as long as e-e scattering processes are dominant and umklapp scattering is negligible. These results are especially relevant to the bulk of wide and long suspended high-mobility graphene sheets.

cond-mat.mes-hall↗