arXiv subjects

Xinlei Yue

Publications and source records attributed to Xinlei Yue.

5 recordsLinked to original sources

arXiv2026

Quantum Phase Transitions and Fractional Quantized Anomalous Hall Insulators in Rhombohedral Graphene

Fractional quantum anomalous Hall effect (FQAHE) has been discovered in twisted MoTe$_2$ and rhombohedral graphene/hBN moiré superlattices. Such van der Waals heterostructures feature a tuning knob of gate displacement field $D$, which is absent from the conventional fractional quantum Hall systems in two-dimensional electron gases. $D$ plays a critical role in engineering FQAHE and other emergent quantum states and provides an exciting new opportunity to explore their quantum phase transitions. However, the microscopic details of such transitions and temperature-dependent transport have remained mostly elusive. Here we report systematic resistance measurements in rhombohedral pentalayer graphene/hBN moiré superlattices. We found that the displacement field-driven phase transitions between Composite Fermi liquid, Fermi liquid, Fractional Chern insulators, and insulating states are described by semi-circle relations of the longitudinal and transverse resistivities (or conductivities), largely unexplored in the fractional quantum Hall systems. This agrees with a spatially separated two-phase picture for the phase transitions and further indicates a new insulator phase--fractional quantized anomalous Hall insulator. By comparing the temperature-dependence of longitudinal resistance with the thermal activation model, we estimated the transport gap sizes in three fractional Chern insulator states. Our work shed light on the quantum and temperature evolutions of fractional Chern insulator states--providing necessary background for anyon-braiding and gate-defined junctions in rhombohedral graphene.

cond-mat.mes-hall↗

arXiv2026

Electromagnetic Response of a Half-Filled Chern Band near Topological Criticality

We evaluate electromagnetic-response observables in a half-filled Chern band, across a topological phase transition between a composite Fermi liquid (CFL) and a Fermi liquid (FL) phase. While a sharp gapped plasma mode exists deep in the CFL phase, we demonstrate that it is damped near the proposed continuous phase transition between CFL and FL. This plasmon-damping phenomenon originates from emergent gauge fields and a Dirac-fermion-like spectrum. Similar features also occur in other continuous deconfined topological phase transitions, such as the Laughlin to superfluid transition in a bosonic system. In particular, this damping behavior extends over a finite range across the phase boundary, and, hence, we expect it to persist even when the transition is weakly first-order. Furthermore, we analyze the characteristic conductivity behavior, such as the Drude weight, the wavevector-dependent conductivity, the chiral mirror effect, and thermodynamic behavior, including compressibility and magnetic susceptibility across these topological phase transitions.

cond-mat.str-el↗

arXiv2024

Electronic Excitations in the Bulk of Fractional Quantum Hall States

We analyze electronic excitations (excitations generated by adding or removing one electron) in the bulk of fractional quantum Hall states in Jain sequence states, using composite fermion Chern-Simons field theory. Starting from meanfield approximation in which gauge field fluctuations are neglected, we use symmetry to constrain the possible composite fermion states contributing to electronic Green's function and expect discrete infinitely-sharp peaks in the electronic spectral function. We further consider the electronic excitations in particle-hole conjugate fractional quantum hall states. Gauge field fluctuations play an increasingly important role in the electron spectral function as the filling factor approaches 1/2, and evolve the discrete coherent peaks into a broad continuum even in the absence of impurities. At that limit, we switch to the electron perspective and calculate the electron spectral function via linked cluster approximation from the low to intermediate energy range. Finally, we compare our results with recent experiments.

cond-mat.mes-hall↗

arXiv2023

Probing a Bose Metal via Electrons: Inescapable non-Fermi liquid scattering and pseudogap physics

Non-Fermi liquid behavior and pseudogap formation are among the most well-known examples of exotic spectral features observed in several strongly correlated materials such as the hole-doped cuprates, nickelates, iridates, ruthenates, ferropnictides, doped Mott organics, transition metal dichalcogenides, heavy fermions, d- and f- electron metals, etc. We demonstrate that these features are inevitable consequences when fermions couple to an unconventional Bose metal [1] mean field consisting of lower-dimensional coherence. Not only do we find both exotic phenomena, but also a host of other features that have been observed e.g. in the cuprates including nodal anti-nodal dichotomy and pseudogap asymmetry(symmetry) in momentum(real) space. Obtaining these exotic and heretofore mysterious phenomena via a mean field offers a simple, universal, and therefore widely applicable explanation for their ubiquitous empirical appearance. [1] A. Hegg, J. Hou, and W. Ku, Geometric frustration produces long-sought Bose metal phase of quantum matter, Proceedings of the National Academy of Sciences Nov 2021, 118 (46) e2100545118.

cond-mat.str-el↗

arXiv2020

Designer spin order in diradical nanographenes

The magnetic properties of carbon materials are at present the focus of an intense research effort in physics, chemistry and materials science due to their potential applications in spintronics and quantum computations. Although the presence of spins in open-shell nanographenes has been recently confirmed, the ability to control magnetic coupling sign has remained elusive, but the most desirable. Here, we demonstrate an effective approach of engineering magnetic ground states in atomically precise open-shell bipartite/nonbipartite nanographenes using combined scanning probe techniques and mean-field Hubbard model calculations. The magnetic coupling sign between two spins has been controlled via breaking bipartite lattice symmetry of nanographenes. In addition, the exchange-interaction strength between two spins has been widely tuned by finely tailoring their spin density overlap, realizing a large exchange-interaction strength of 42 meV. Our demonstrated method provides ample opportunities for designer above-room-temperature magnetic phases and functionalities in graphene nanomaterials.

cond-mat.mes-hall↗