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Nabin Upadhya Dhakal

Publications and source records attributed to Nabin Upadhya Dhakal.

2 recordsLinked to original sources

Study of Twistronics Induced Superconductivity in Twisted Bilayer Graphene

This work investigates the electronic properties of twisted bilayer graphene (TBG) through computational calculations, with the aim of understanding the emergence of flat bands and conditions favorable for superconductivity close to the magic angle. This study utilizes a k\cdot p continuum model, and the low-energy Hamiltonians are derived from angle-dependent datasets provided by Carr et al. Using this model, the band structure, density of states (DoS), and Fermi velocity are systematically calculated across a range of twist angles. The calculations are performed by discretizing high-symmetry paths in the moire Brillouin zone for band structure calculations, uniformly sampling a square grid for DoS analysis, and employing finite-difference methods to evaluate the Fermi velocity near the Dirac points. The results identify a narrow magic-angle window around $θ\approx 0.98^\circ-1.00^\circ$, where the bands become nearly dispersionless, the DoS exhibits a sharp peak, and the Fermi velocity is strongly suppressed. This computational framework does not directly predict superconductivity, but rather establishes the electronic foundation for exploring flat-band physics and correlation-driven phenomena such as unconventional superconductivity in twisted bilayer graphene.

cond-mat.mes-hall↗

Energy-dependent anisotropy of cosmic-ray muons: A twelve-year study with IceCube Neutrino Observatory

We present a comprehensive, energy-resolved study of cosmic-ray muon anisotropy using 12 years (2011-2023) of data from the IceCube Neutrino Observatory, comprising 7.92 x 10^11 events in the 13 TeV to 5.3 PeV energy range. Dividing the spectrum at log-scale energy 5 GeV, we contrast low- and high-energy anisotropy features via sidereal modulation, angular profiles, Fourier analysis, and full-sky HEALPix mapping. Gaussian and power-law fits to energy distributions are evaluated using chi-squared, reduced chi-squared, and Bayesian Information Criterion. Results show strong dipolar and large-scale anisotropy at low energies, likely due to geomagnetic and atmospheric effects, while high-energy muons display weaker, more localized structures consistent with reduced scattering and source-related anisotropy. Energy distributions are well fit by Gaussians, especially in the 6.5 to 100 bin, validating IceCube's reconstruction at PeV scales. These findings confirm energy-dependent anisotropy and support cosmic-ray diffusion models.

astro-ph.HE↗