arXiv subjects

Yu-Biao Wu

Publications and source records attributed to Yu-Biao Wu.

9 recordsLinked to original sources

arXiv2026

Fractional Chern insulator with higher Chern number in optical lattice

Fractional Chern insulators arise in topologically nontrivial flat bands, characterized by an integer Chern number C that corresponds to the number of dissipationless edge states in the non-interacting regime. Higher Chern numbers can replicate the physics of higher Landau levels and often confer enhanced topological robustness. However, realizing correlated fractional phases with higher Chern numbers in such flat band systems remains challenging. Here, we propose an interlayer coupling scheme to generate higher Chern numbers in a flat-band system, where the interlayer coupling transforms two C = 1 bands in a bilayer checkerboard lattice into a single flat band with C = 2 by lifting their degeneracy and merging their topological indices. Exact diagonalization calculation reveals that this engineered band hosts two fractional Chern insulator states with C = 2/3 and 2/5, respectively. An experimental setup is proposed to simulate these states using cold alkaline-earth-like atoms in an effective bilayer optical lattice. Our work provides a general and widely applicable strategy for constructing higher Chern number flat bands, opening a pathway to explore exotic fractional quantum phases.

cond-mat.str-el↗

arXiv2025

Spin-Orbit Coupling-Driven Chirality Switching of Spin Waves in Altermagnets

Altermagnets host intrinsically chirality-splitting spin waves, which offer an ideal platform for chirality-based computing with low energy consumption and fast dynamics. However, achieving precise and efficient control over spin-wave chirality remains a challenge. Here, we propose a mechanism to switch the chirality of spin waves in altermagnets via electrically induced Rashba spin-orbit coupling (SOC), which is free of tuning external fields. For in-plane spin polarization, SOC introduces a splitting effect opposite to the altermagnetism, leading to spin inversion in the electronic energy bands and chirality reversal in the spin-wave dispersion. By tuning SOC strength, the chirality splitting of spin waves can be controllably modified, enabling chirality switching at fixed resonance conditions, which results in the reversal of transverse spin susceptibility. We further design an experimental setup based on an altermagnet/antiferromagnet heterostructure to realize this mechanism. Our work establish a pathway toward efficient electrical control of spin-wave chirality in altermagnets, facilitating the development of chirality-based spintronic devices.

cond-mat.mes-hall↗

arXiv2024

Visualization of Skyrmion-Superconducting Vortex Pairs in a Chiral-Magnet-Superconductor Heterostructure

Magnetic skyrmions, the topological states possessing chiral magnetic structure with nontrivial topology, have been widely investigated as a promising candidate for spintronic devices. They can also couple with superconducting vortices to form skyrmion-vortex pairs, hosting Majorana zero mode, which is a potential candidate for topological quantum computing. Many theoretical proposals have been put forward on constructing skyrmion-vortex pairs in heterostructures of chiral magnets and superconductors. Nevertheless, how to generate skyrmion-vortex pairs in a controllable way experimentally remains a significant challenge. We have designed a heterostructure of a chiral magnet and superconductor [Ta/Ir/CoFeB/MgO]7/Nb in which zero field Néel-type skyrmions can be stabilized and the superconducting vortices can couple with the skyrmions when Nb is in the superconducting state. We have directly observed the formation of skyrmion-superconducting vortex pairs that is dependent on the direction of the applied magnetic field. Our results provide an effective method to manipulate the quantum states of skyrmions with the help of superconducting vortices, which can be used to explore new routines to control the skyrmions for spintronics devices.

cond-mat.supr-con↗

arXiv2024

Emergence of charge density wave and superconducting phase transitions through Lorentz-invariant interactions in the Haldane-Hubbard model

We derive Lorentz-invariant four-fermion interactions, including Nambu-Jona-Lasinio type and superconducting type, which are widely studied in high-energy physics, from the honeycomb lattice Hamiltonian with Hubbard interaction. We investigate the phase transitions induced by these two interactions and consider the effects of the chemical potential and magnetic flux (Haldane mass term) on these phase transitions. We find that the charge-density-wave and superconductivity generated by the attractive interactions are mainly controlled by the chemical potential, while the magnetic flux delimits the domain of phase transition. Our analysis underscores the influence of the initial topological state on the phase transitions, a facet largely overlooked in prior studies. We present experimental protocols using cold atoms to verify our theoretical results.

cond-mat.str-el↗

arXiv2024

Chiral symmetry breaking in the pseudo-quantum electrodynamics with non-Abelian four-fermion interactions

In the context of 2+1 dimensional Dirac materials, we consider electromagnetic interactions alongside a type of spin-dependent Hubbard interaction. The former is described by PQED theory, while the latter corresponds to an effective theory represented by the $SU(N_c)$ Thirring model. Employing Hubbard-Stratonovich transformation and large N expansion in the model yields a non-local $SU(N_c)$ Yang-Mills action. Subsequently, we solve Schwinger-Dyson equations to obtain the self-energy function of the fermion propagator, from which we determine the critical fermion flavor number $N^c_f$ and critical fine structure constant $α_c$ indicative of chiral symmetry breaking. Our findings suggest that as the non-Abelian color number $N_c$ increases, the minimum value of the critical fermion flavor number monotonically increases, while the maximum value of the critical fine structure constant decreases accordingly, rendering the system more susceptible to chiral symmetry breaking.

hep-th↗

arXiv2024

Strongly-tilted field induced Hamiltonian dimerization and nested quantum scars in the 1D spinless Fermi-Hubbard model

We investigate the quantum dynamics of the 1D spinless Fermi-Hubbard model with a linear-tilted potential. Surprisingly in a strong resonance regime, we show that the model can be described by the kinetically constrained effective Hamiltonian, and it can be spontaneously divided into two commuting parts dubbed Hamiltonian dimerization, which consist of a sum of constrained two-site hopping terms acting on odd or even bonds. Specifically it is showed that each part can be independently mapped onto the well-known PXP model, therefore the dimerized Hamiltonian is equivalent to a two-fold PXP model. As a consequence, we numerically demonstrate this system can host the so-called quantum many-body scars, which present persistent dynamical revivals and ergodicity-breaking behaviors. However in sharp contrast with traditional quantum many-body scars, here the scarring states in our model driven by different parts of Hamiltonian will oscillate in different periods, and those of double parts can display a biperiodic oscillation pattern, both originating from the Hamiltonian dimerization. Besides, the condition of off-resonance is also discussed and we show the crossover from quantum many-body scar to ergodicity breaking utilizing level statistics. Our model provides a platform for understanding the interplay of Hilbert space fragmentation and the constrained quantum systems

cond-mat.str-el↗

arXiv2023

Tunable boson-assisted finite-range interaction and engineering Majorana corner modes in optical lattices

Nonlocal interaction between ultracold atoms trapped in optical lattices can give rise to interesting quantum many-body phenomena. However, its realization usually demands unconventional techniques, for example the artificial gauge fields or higher-orbit Feshbach resonances, and is not highly controllable. Here, we propose a valid and feasible scheme for realizing a tunable finite-range interaction for spinless fermions immersed into the bath of bosons. The strength of the effective interaction for the fermionic subsystem is artificially tunable by manipulating bosons, ranging from the repulsive to attractive regime. And the interaction distance is locked to the hopping of bosons, making the finite-range interaction perfectly clean for the fermionic subsystem. Specifically we find that, by introducing an additional staggered hopping of bosons, the proposal is readily applied to search the Majorana corner modes in such a spinless system, without implementation of complex artificial gauge fields, which is totally distinct from existing results reported in spinful systems. Therefore this scheme provides a potential platform for exploring the unconventional topological superfluids and other nontrivial phases induced by long-range interactions in ultracold atoms.

cond-mat.quant-gas↗

arXiv2021

Multiorder topological superfluid phase transitions in a two-dimensional optical superlattice

Higher-order topological superfluids have gapped bulk and symmetry-protected Majorana zero modes with various localizations. Motivated by recent advances, we present a proposal for synthesizing multi-order topological superfluids that support various Majorana zero modes in ultracold atomic gases. For this purpose, we use the two-dimensional optical superlattice that introduces a spatial modulation to the spin-orbit coupling in one direction, providing an extra degree of freedom for the emergent higher-order topological state. We find the topologically trivial superfluids, first-order and second-order topological superfluids, as well as different topological phase transitions among them with respect to the experimentally tunable parameters. Besides the conventional transition characterized by the Chern number associated with the bulk gap closing and reopening, we find the system can support the topological superfluids with Majorana corner modes, but the topological phase transition undergoes no gap-closing of bulk bands. Instead, the transition is refined by the quadrupole moment and signaled out by the gap-closing of edge states. The proposal is based on the $s$-wave interaction and is valid using existing experimental techniques, which unifies multi-order topological phase transitions in a simple but realistic system.

cond-mat.quant-gas↗

arXiv2020

Effective Hamiltonian with tunable mixed pairing in driven optical lattices

Mixed pairing in ultracold Fermi gases can give rise to interesting many-body phases, such as topological nontrivial superfluids that support Majorana zero modes (MZMs) with various spatial configurations. Unfortunately, in ordinary lattice systems, the topological phase and the associated MZMs are suppressed by the dominant $s$-wave pairing. Here we present a proposal for engineering effective Hamiltonians with tunable mixed on- and off-site pairing based on driven optical lattices. The on- and off-site pairing can be changed independently by means of a periodical driving field rather than magnetic Feshbach resonances. It paves the way for suppressing the dominant on-site interaction that frustrates the emergence of topological superfluids and for synthesizing MZMs localized in edges or corners.

cond-mat.quant-gas↗