arXiv subjects

Jianing Tan

Publications and source records attributed to Jianing Tan.

7 recordsLinked to original sources

arXiv2026

Interlayer sliding direction as a symmetry selector in altermagnetic bilayer Fe2WS4: Switchable anomalous Hall and anomalous valley Hall effects

Altermagnets combine compensated collinear magnetic order with momentum-dependent spin splitting, offering a promising platform for coupling spin and valley degrees of freedom with ferroelectricity and Berry-curvature driven transport in the absence of net magnetization. However, achieving nonvolatile and selective control of these intertwined degrees of freedom remains a key challenge. Here, using first-principles calculations, we show that the direction of interlayer sliding serves as a symmetry selective control parameter in altermagnetic bilayer Fe2WS4. Diagonal sliding breaks inversion symmetry and produces two sliding ferroelectric states with opposite out-of-plane polarizations. Reversal of the ferroelectric polarization switches the momentum-dependent spin texture and reverses the anomalous Hall conductivity, revealing strong magnetoelectric coupling and enabling a ferroelectrically switchable anomalous Hall effect. In contrast, axial sliding preserves inversion symmetry but breaks the crystalline symmetry relating the X and Y valleys, leading to reversible valley polarization and a switchable anomalous valley Hall effect. These results establish the direction of interlayer sliding as a nonvolatile symmetry selector for controlling ferroelectricity, spin texture, valley polarization, and Hall transport responses in two-dimensional altermagnetic bilayers.

cond-mat.mtrl-sci↗

arXiv2026

Multistate ferroelectricity and switchable layer-locked anomalous valley Hall effects in bilayer ReIrGe2Se6

Two-dimensional multiferroic materials, which combine magnetic and ferroelectric (FE) orders with strong magnetoelectric coupling, represent ideal platforms for high-density information storage and low-power multistate electronics. However, the intrinsic bistability of conventional ferroelectricity poses a substantial challenge to realizing multiple nonvolatile states and programmable Berry-curvature driven transport responses within a single material. Here, using first-principles calculations, we predict multistate ferroelectricity in AA0-stacked bilayer ReIrGe2Se6. The system hosts four energetically stable FE polarization configurations, among which three are connected through reversible switching pathways, while the fourth exhibits a unidirectional switching pathway. The distinct FE configurations further give rise to a cyclic semiconductor-metal-semiconductor evolution in the electronic structure. Notably, FE polarization switching is intimately coupled to layer degrees of freedom and Berry curvature. The layer-dependent electrostatic potential associated with different FE configurations controls the layer character of the band-edge states, thereby locking the Berry curvature to specific layer channels. As a result, bilayer ReIrGe2Se6 enables switching between an anomalous valley Hall effect and a layer-locked anomalous valley Hall effect, providing nonvolatile control of layer, valley, and spin-resolved transport responses. In addition, magnetization reversal switches the valley and spin channels while preserving the layer-resolved character. These results establish bilayer ReIrGe2Se6 as a multistate ferroelectric platform for programmable Berry-curvature related transport, offering microscopic insight into topology based multifunctional electronic and valleytronic devices.

cond-mat.mtrl-sci↗

arXiv2026

Fractional quantum ferroelectric control of spin-valley locking and valley Hall effects in altermagnetic monolayer Cr2S2

Fractional quantum multiferroics, arising from the coupling between fractional quantum ferroelectricity (FQFE) and altermagnetism (AM), provide a promising platform for nonvolatile control of momentum dependent spin splitting in systems with zero net magnetization. However, extending this FQFE-AM coupling to valley degrees of freedom and Berry curvature driven valley Hall effects remains largely unexplored. Here, using first-principles calculations, we demonstrate that monolayer Cr2S2 realizes a two dimensional FQFE-AM platform with two switchable FQFE states connected by composite symmetry operations combining a fractional lattice translation with time reversal or parity-time reversal. We show that FQFE switching reverses the AM spin-polarized band structure and interchanges the spin characters of the X and Y valleys without rotating the N\'eel vector, thereby enabling polarization switchable spin-valley locking. Moreover, the two FQFE states exhibit reversed Berry curvature distributions, which, together with the switched spin-valley locking, enable polarization controlled valley Hall effects under both electron and hole doping. These results demonstrate a symmetry based mechanism for nonvolatile electrical control of AM spin splitting, spin-valley locking, and valley Hall effects, offering a general route toward low-power valleytronic devices based on FQFE-AM coupling.

cond-mat.mtrl-sci↗

arXiv2026

Strain-tunable multipiezo effects in Janus monolayer Cr2SSe: Selective reversal of valley polarization and single-spin-channel anomalous valley Hall effect

Altermagnetism, the third class of collinear magnetic order, uniquely combines a zero net magnetization with spin polarized bands in reciprocal space, opening new avenues for two dimensional valleytronics and spintronics. Here, using first principles calculations, we predict that the Janus monolayer Cr2SSe, which possesses intrinsic inversion symmetry breaking, hosts a strain tunable multipiezo effect and exhibits distinctive valleytronic properties. The system displays pronounced spin splitting and band inversion at the X and Y high symmetry points in the Brillouin zone, giving rise to robust spin-valley locking. The degeneracy of these valleys is protected by diagonal mirror symmetry. Application of uniaxial strain breaks this symmetry, concurrently inducing piezovalley, piezoelectric, and piezomagnetic responses, a manifestation of the multipiezo effect. Critically, strain applied along orthogonal crystallographic directions yields opposite valley polarization, while under small compressive strain, we achieve selective reversal of valley polarization, enabling independent control of valence and conduction band valleys and promoting a single-spin-channel anomalous valley Hall effect. These findings establish a pathway for low-power, non volatile manipulation of valley degrees of freedom and enhanced spin transport efficiency, providing a theoretical foundation for the design of energy-efficient valleytronic devices.

cond-mat.mtrl-sci↗

arXiv2026

All-electrical switching of spin texture in a strain-tunable 2D Janus ferroelectric altermagnet

Altermagnetism (AM), a collinear magnetic phase with momentum-dependent spin splitting, is a promising candidate for strong magnetoelectric coupling. However, realizing direct and tunable coupling between ferroelectricity (FE) and AM within a single two-dimensional (2D) material remains an outstanding challenge. Here, based on first-principles calculations, we identify the distorted phase of monolayer Janus VOClBr as an intrinsic 2D FE-AM. This phase demonstrates robust magnetoelectric coupling, as evidenced by a complete reversal of momentum-space spin polarization upon FE switching, and further supported by spin texture analysis and the magneto-optical Kerr effect. Notably, the FE properties are highly strain-tunable: biaxial compression strain of -4% reduces the FE polarization switching barrier by approximately 87%, whereas a tensile strain of +3% induces a phase transition to an antiferromagnet. Leveraging the lock-in between the electrically controlled spin texture and the magneto-optical Kerr effect signal, we propose a non-volatile, polymorphic spintronic memory device featuring all-electrical writing and optical readout. This work establishes 2D FE-AMs as a versatile platform for coupled ferroic orders and paves the way for voltage-controlled, multifunctional spin-logic devices.

cond-mat.mtrl-sci↗

arXiv2026

Dual-Switch Control of a Layer-Locked Anomalous Valley Hall Effect in a Sliding Ferroelectric Antiferromagnet

The integration of ferroelectric (FE) and antiferromagnetic (AFM) orders in twodimensional (2D) materials provides a promising avenue for the nonvolatile control of coupled spin and valley degrees of freedom, a capability central to advancing spinvalleytronics. However, realizing a single material system where these quantum states can be independently and reversibly manipulated by distinct stimuli, a prerequisite for multifunctional devices, has remained elusive. Here, we demonstrate a dual-switch mechanism in bilayer VS2, a room-temperature FE-AFM system, that enables electrical and magnetic control of a layer-locked anomalous valley Hall effect (AVHE). First-principles calculations reveal that interlayer sliding breaks spatial inversion symmetry, inducing a switchable out-of-plane FE polarization that coexists with interlayer AFM. The spin-orbit coupled valley polarization can be reversibly switched either by FE polarization reversal or by a magnetic-field-induced spin-flip transition, confirming the existence of electrically and magnetically addressable valley states. The Berry curvature exhibits both valley-contrasting and layer-locked characteristics, which underpin a switchable Hall response. Notably, electric and magnetic switching are functionally equivalent in modulating valley, layer, and spin indices, revealing strong magnetoelectric coupling. This work establishes a multidegree-of-freedom operational paradigm in 2D multiferroics and opens a viable design pathway toward multi-state memory and spin-valleytronic logic devices.

cond-mat.mes-hall↗

arXiv2018

Spatial search for a general multi-vertex state on graph by continuous-time quantum walks

In this work, we consider the spatial search for a general marked state on graphs by continuous time quantum walks. As a simplest case, we compute the amplitude expression of the search for the multi-vertex uniform superposition state on hypercube, and find that the spatial search algorithm is optimal for the two-vertex uniform state. However, on general graphs, a common formula can't be obtained for searching a general non-uniform superposition state. Fortunately, a Laplacian spectrum condition which determines whether the associated graph could be appropriate for performing the optimal spatial search is presented. The condition implies that if the proportion of the maximum and the non-zero minimum Laplacian eigenvalues is less or equal to 1+sqrt(1/2), then the spatial search is optimal for any general state. At last, we apply this condition to three kind graphs, the induced complete graph, the strongly regular graph and the regular complete multi-partite graphs. By the condition, one can conclude that these graphs will become suitable for optimal search with properly setting their graph parameters.

math-ph↗