arXiv subjects

Mohit Kumar Jat

Publications and source records attributed to Mohit Kumar Jat.

5 recordsLinked to original sources

arXiv2026

Layer-Polarization-Driven Metal-Insulator Transition in multi-band Graphene Moire' Superlattices

Graphene/hBN moiré superlattices provide a highly tunable platform for exploring emergent quantum phases in low-dimensional systems. Here, we investigate the moiré superlattice formed between hBN and ABA-stacked trilayer graphene (TLG), an inherently multi-band system. We demonstrate that the moiré potential is not merely a perturbation but a tool to hybridize the distinct massless and massive electronic sectors of TLG. By applying a perpendicular displacement field to tune layer polarization, we drive a fundamental reconstruction of the electronic band structure. Specifically, increasing the displacement field evolves the system from a multi-band regime to an effectively single-band regime at low energies, accompanied by a metal--insulator transition at the hole-doped secondary Dirac point. This transition originates from a redistribution of carriers across graphene layers that selectively enhances their coupling to the extrinsic moiré potential. Quantum capacitance measurements provide direct evidence for the suppression of the density of states at the hole-side secondary Dirac point, consistent with gap opening and the emergence of a displacement-field-tuned band gap. Theoretical calculations reproduce these observations and identify layer-selective coupling to the moiré potential as the underlying mechanism. These results demonstrate electrical control of an emergent insulating phase in a low-dimensional moiré system, and highlight that layer polarization and layer-selective coupling in multi-band moiré heterostructures provide a powerful route for engineering topological and correlated phases through band structure reconstruction and electron interactions.

cond-mat.mes-hall↗

arXiv2026

Coexisting Massive and Massless Dirac Fermions in Moire'-Reconstructed Bilayer Graphene

We report the emergence of massless Dirac fermions in moiré-reconstructed bands of bilayer graphene (BLG) aligned with hexagonal boron nitride (hBN). Magnetotransport measurements reveal that while the primary BLG band retains a parabolic dispersion with a Berry phase of $2π$, the moiré-induced secondary bands at $n/n_0 = \pm 4$ host chiral massless quasiparticles with a Berry phase $π$ and a Fermi velocity $v_m \approx 3.6 \times 10^5 \mathrm{m s^{-1}}$. This transition from massive to massless carriers arises from topological band reconstruction driven by the hBN moiré potential. Our results demonstrate that moiré engineering in BLG/hBN offers a powerful route to tune band topology and realize coexisting Dirac and massive fermions within a single crystalline platform.

cond-mat.mes-hall↗

arXiv2024

Controlling Umklapp scattering in bilayer graphene moir'e superlattice

In this Letter, we present experimental findings on electron-electron scattering in a two-dimensional moir'e heterostructure with tunable Fermi wave vector, reciprocal lattice vector, and band gap. We achieve this in high-mobility aligned heterostructures of bilayer graphene (BLG) and hBN. Around half-filling, the primary contribution to the resistance of BLG/hBN aligned superlattices arises from electron-electron Umklapp (Uee) scattering, making the resistance of graphene/hBN moir'e devices significantly larger than that of non-aligned devices (where Uee is forbidden). We quantify the strength of the Uee scattering and find that it follows a universal scaling with Fermi energy and has a non-monotonic dependence on the charge carrier density. The Uee scattering is strongly electric field tunable and affected by layer-polarization of BLG. It has a strong particle-hole asymmetry - the resistance when the chemical potential is in the conduction band is significantly lesser than when it is in the valence band, making the electron-doped regime more practical for potential applications.

cond-mat.mes-hall↗

arXiv2023

Higher-order Bragg gaps in the electronic band structure of bilayer graphene renormalized by recursive supermoiré potential

This letter presents our findings on the recursive band gap engineering of chiral fermions in bilayer graphene doubly aligned with hBN. By utilizing two interfering moiré potentials, we generate a supermoiré pattern which renormalizes the electronic bands of the pristine bilayer graphene, resulting in higher-order fractal gaps even at very low energies. These Bragg gaps can be mapped using a unique linear combination of periodic areas within the system. To validate our findings, we used electronic transport measurements to identify the position of these gaps as functions of the carrier density and establish their agreement with the predicted carrier densities and corresponding quantum numbers obtained using the continuum model. Our work provides direct experimental evidence of the quantization of the area of quasi-Brillouin zones in supermoiré systems. It fills essential gaps in understanding the band structure engineering of Dirac fermions by a recursive doubly periodic superlattice potential.

cond-mat.mes-hall↗

arXiv2022

Experimental observation of spin-split energy dispersion in high-mobility single-layer graphene/WSe2 heterostructures

Proximity-induced spin-orbit coupling in graphene has led to the observation of intriguing phenomena like time-reversal invariant $\mathbb{Z}_2$ topological phase and spin-orbital filtering effects. An understanding of the effect of spin-orbit coupling on the band structure of graphene is essential if these exciting observations are to be transformed into real-world applications. In this research article, we report the experimental determination of the band structure of single-layer graphene (SLG) in the presence of strong proximity-induced spin-orbit coupling. We achieve this in high-mobility hBN-encapsulated SLG/WSe2 heterostructures through measurements of quantum oscillations. We observe clear spin-splitting of the graphene bands along with a substantial increase in the Fermi velocity. Using a theoretical model with realistic parameters to fit our experimental data, we uncover evidence of a band gap opening and band inversion in the SLG. Further, we establish that the deviation of the low-energy band structure from pristine SLG is determined primarily by the valley-Zeeman SOC and Rashba SOC, with the Kane-Mele SOC being inconsequential. Despite robust theoretical predictions and observations of band-splitting, a quantitative measure of the spin-splitting of the valence and the conduction bands and the consequent low-energy dispersion relation in SLG was missing -- our combined experimental and theoretical study fills this lacuna.

cond-mat.mes-hall↗