arXiv subjects

Jackson Kuklin

Publications and source records attributed to Jackson Kuklin.

2 recordsLinked to original sources

arXiv2026

Magnetic Field Reorganization of Electronic States in Moir\'e Bilayer Graphene

Magnetic fields are widely used to diagnose quantum phases in two-dimensional systems through quantum oscillations or by tuning spin and valley polarizations, but magnetic fields can also reshape the underlying electronic structure. Here, using a bilayer graphene/hBN moir\'e system, we reveal a rich magnetic field induced evolution of the semiclassical orbit network, encompassing Lifshitz transitions, magnetic breakdown, and scattering between coexisting electron and hole pockets. At magnetic fields of 1 T to 2 T, quantum oscillation frequencies and the Hall density change markedly over a broad carrier density range, signaling magnetic breakdown and magnetic Lifshitz transitions. This evolution is valley contrasting: Berry curvature hot spots near the breakdown junctions enhance magnetic breakdown in the K valley while suppressing it in the K$^\prime$ valley, whereas valley-antisymmetric orbital magnetic moments split the corresponding Lifshitz transitions. The resulting valley-selective trajectories manifest at higher fields as valley-symmetry-breaking Hofstadter gaps. At elevated temperatures and low magnetic fields, scattering between coexisting electron and hole pockets produces nearly density-independent resistance oscillations whose frequency tracks the sum of their Fermi surface areas, persisting after conventional Onsager oscillations are thermally washed out. Our results provide a unified picture of how modest magnetic fields reorganize moir\'e electronic states as the system evolves from semiclassical transport toward the Hofstadter regime.

cond-mat.mes-hall↗

arXiv2026

Contrasting $\Gamma$- and K-Valley Moir\'e Physics in Twisted Monolayer/Bilayer WSe$_2$

Electronic orbital character plays a central role in determining electronic correlations, spin-orbit coupling, dimensionality, and ultimately the quantum phases of condensed-matter systems. Two-dimensional moir\'e materials have emerged as highly tunable platforms for exploring correlated phenomena, but the role of orbital degrees of freedom remains largely unexplored. Here, we identify twisted monolayer/bilayer WSe$_2$ as a platform in which displacement-field tuning enables moir\'e physics to be realized in both the $K$ and $\Gamma$ valleys. The distinct orbital characters of these valleys give rise to contrasting correlated phases at moir\'e filling factors $\nu=1$ and $\nu=1/3$. At $\nu=1$, the $K$-valley state is a weak insulator, consistent with an antiferromagnetic state near a van Hove singularity in the intermediate-coupling regime, similar to that observed in twisted bilayer WSe$_2$. In contrast, the $\Gamma$-valley state exhibits a pronounced Pomeranchuk effect, consistent with proximity to a Mott transition. At $\nu=1/3$, the $K$ valley hosts a robust generalized Wigner crystal, whereas the $\Gamma$-valley state lies near the crystallization boundary and again exhibits a Pomeranchuk effect, with localization enhanced by increasing temperature or magnetic field. Our work highlights the importance of orbital character in defining quantum phases in moir\'e systems, and identify the $\Gamma$ valley as a promising platform for exploring correlated phenomena near quantum phase transitions, where competing phases and enhanced fluctuations may give rise to unconventional phases.

cond-mat.mes-hall↗