arXiv subjects

Wentian Lu

Publications and source records attributed to Wentian Lu.

8 recordsLinked to original sources

arXiv2026

Collective and separate metal-insulator transitions in correlated vanadium dioxide

Deciphering the complicated interplay between collective and separate behaviors lies at the heart of first-order metal-insulator transition (MIT) in correlated electron systems, enabling the rational design of exotic electronic states and functionalities. The critical balance between collective and separate behaviors defines a fundamental collective length scale, typically shorter than 5 nm, that governs emergent quantum orders, yet active control over this dichotomy remains elusive. Here, we realize on-demand manipulation of the collective and separate MIT within the correlated VO2 system in a reversible fashion. Artificially designing the oxygen deficiency in VO2/VO2-x homojunction fosters a collective MIT with an extended collective length scale, whereas the introduction of a TiO2 interlayer drives a crossover from this collective to a two-step separate MIT via decoupling of the electronic order parameter. Incorporating mobile hydrogens into the VO2/TiO2/VO2-x trilayer enables reversible control over electronic phase modulations, transitioning a two-step MIT towards either a one-step MIT or collective electron localization. This ionic control over the electronic band structure of VO2 flexibly triggers multi-state MIT, a process governed by hydrogen-related band filling. Our findings transform the collective length scale from a passive threshold into a dynamic design parameter, establishing a viable handle for engineering collective and separate MIT for adaptive correlated electronics.

cond-mat.str-el↗

arXiv2025

Silicon-Compatible Ionic Control over Multi-State Magnetoelectric Phase Transformations in Correlated Oxide System

Realizing room-temperature ferromagnetic insulators, critical enablers for low-power spintronics, is fundamentally challenged by the long-standing trade-off between ferromagnetic ordering and indirect exchange interactions in insulators. Ionic evolution offers tempting opportunities for accessing exotic magnetoelectric states and physical functionality beyond conventional doping paradigm via tailoring the charge-lattice-orbital-spin interactions. Here, we showcase the precise magneto-ionic control over magnetoelectric states in LSMO system, delicately delivering silicon-compatible weakly ferromagnetic insulator state above room temperature. Of particular note is the decoupling of ion-charge-spin interplay in correlated LSMO system, a primary obstacle in clarifying underlying physical origin, with this process concurrently giving rise to an emergent intermediate state characterized by a weakly ferromagnetic half-metallic state. Benefiting from the SrTiO3 buffer layer as epitaxial template to promote interfacial heterogeneous nucleation, hydrogenation enables diverse magnetoelectric states in LSMO integrated on silicon, fully compatible with traditional semiconductor processing. Assisted by theoretical calculations and spectroscopic techniques, hydrogen-induced magnetoelectric transitions in LSMO are driven by band-filling control and suppression in double exchange interaction. Our work not only defines a novel design paradigm for exploring exotic quantum states in correlated system, with transformative potential for spintronics, but also fundamentally unveils the physical origin behind ionic evolution via disentangling the ion-charge-spin coupling.

cond-mat.mtrl-sci↗

arXiv2025

Manipulating the hydrogen-induced insulator-metal transition through artificial microstructure engineering

Hydrogen-associated filling-controlled Mottronics within electron-correlated system provides a groundbreaking paradigm to explore exotic physical functionality and phenomena. Dynamically controlling hydrogen-induced phase transitions through external fields offers a promising route for designing protonic devices in multidisciplinary fields, but faces high-speed bottlenecks owing to slow bulk diffusion of hydrogens. Here, we present a promising pathway to kinetically expedite hydrogen-related Mott transition in correlated VO2 system by taking advantage of artificial microstructure design. Typically, inclined domain boundary configuration and cR-faceted preferential orientation simultaneously realized in VO2/Al2O3 (102) heterostructure significantly lower the diffusion barrier via creating an unobstructed conduit for hydrogen diffusion. As a result, the achievable switching speed through hydrogenation outperforms that of counterpart grown on widely-reported c-plane Al2O3 substrate by 2-3 times, with resistive switching concurrently improved by an order of magnitude. Of particular interest, an anomalous uphill hydrogen diffusion observed for VO2 with a highway for hydrogen diffusion fundamentally deviates from basic Fick's law, unveiling a deterministic role of hydrogen spatial distribution in tailoring electronic state evolution. The present work not only provides a versatile strategy for manipulating ionic evolution, endowing with great potential in designing high-speed protonic devices, but also deepens the understanding of hydrogen-induced Mott transitions in electron-correlated system.

cond-mat.str-el↗

arXiv2025

Magnon-mediated perpendicular magnetization switching by topological crystalline insulator SnTe with high spin Hall conductivity

Magnons possess the ability to transport spin angular momentum in insulating magnetic materials, a characteristic that sets them apart from traditional electronics where power consumption arises from the movement of electrons. However, the practical application of magnon devices demands room temperature operation and low switching power of perpendicular magnetization. Here we demonstrate the low-power manipulation of perpendicular magnetization via magnon torques in SnTe/NiO/CoFeB devices at room temperature. Topological crystalline insulator SnTe exhibits a high spin Hall conductivity of $σ_s \approx 6.1\times 10^4 (\hbar/2e)\cdot (Ω\cdot m)^{-1}$, which facilitates the generation of magnon currents in an antiferromagnetic insulator NiO. The magnon currents traverse the 20-nm-thick NiO layer and subsequently exert magnon torques on the adjacent ferromagnetic layer, leading to magnetization switching. Notably, we achieve a 22-fold reduction in power consumption in SnTe/NiO/CoFeB heterostructures compared to Bi2Te3/NiO/CoFeB control samples. Our findings establish the low-power perpendicular magnetization manipulation through magnon torques, significantly expanding the range of topological materials with practical applications.

cond-mat.mtrl-sci↗

arXiv2024

Magnetic order-dependent giant tunneling magnetoresistance and electroresistance in van der Waals antiferromagnetic-multiferroic tunnel junctions

Antiferromagnetic spintronics exhibits ultra-high operational speed and stability in a magnetic field, holding promise for the realization of next-generation ultra-high-speed magnetic storage. However, theoretical exploration of the electronic transport properties of antiferromagnetic-multiferroic tunnel junction (AMFTJ) devices remains largely unexplored. Here, we design an antiferromagnet/ferroelectric barrier/antiferromagnet van der Waals heterojunction, renamed vdW AMFTJ, using a bilayer MnBi$_2$Te$_4$/In$_2$Se$_3$/bilayer MnBi$_2$Te$_4$ (MBT-2L/IS/MBT-2L) as the prototype. Based on first-principles calculations using the nonequilibrium Green's function method combined with density functional theory, we theoretically investigate the spin-resolved electronic transport properties of this AMFTJ. By manipulating the various possible magnetization directions of the multilayer antiferromagnetic MnBi$_2$Te$_4$ and the ferroelectric polarization direction of the In$_2$Se$_3$ within the junction, sixteen distinct non-volatile resistance states can be revealed and manipulated by applying external biaxial strain and bias voltage. We predict maximum tunneling magnetoresistance (electroresistance) values of $3.79\times10^{4}$\% ($2.41\times10^{5}$\%) in the equilibrium state, which can increase up to $5.01\times10^{5}$\% ($4.97\times10^{5}$\%) under external bias voltage. Furthermore, the perfect spin filtering effect is also present in our AMFTJ. Our results highlight the tremendous potential of the MBT-2L/IS/MBT-2L vdW AMFTJ in non-volatile memory, expanding the application avenues for antiferromagnetic spintronic devices.

cond-mat.mtrl-sci↗

arXiv2024

Giant electrode effect on tunneling magnetoresistance and electroresistance in van der Waals intrinsic multiferroic tunnel junctions using VS2

Van der Waals multiferroic tunnel junctions (vdW-MFTJs) with multiple nonvolatile resistive states are highly suitable for new physics and next-generation storage electronics. However, currently reported vdW-MFTJs are based on two types of materials, i.e., vdW ferromagnetic and ferroelectric materials, forming a multiferroic system. This undoubtedly introduces additional interfaces, increasing the complexity of experimental preparation. Herein, we engineer vdW intrinsic MFTJs utilizing bilayer VS$_2$. By employing the nonequilibrium Green's function combined with density functional theory, we systematically investigate the influence of three types of electrodes (including non-vdW pure metal Ag/Au, vdW metallic 1T-MoS$_2$/2H-PtTe$_2$, and vdW ferromagnetic metallic Fe$_3$GaTe$_2$/Fe$_3$GeTe$_2$) on the electronic transport properties of VS$_2$-based intrinsic MFTJs. We demonstrate that these MFTJs manifest a giant electrode-dependent electronic transport characteristic effect. Comprehensively comparing these electrode pairs, the Fe$_3$GaTe$_2$/Fe$_3$GeTe$_2$ electrode combination exhibits optimal transport properties, the maximum TMR (TER) can reach 10949\% (69\%) and the minimum resistance-area product (RA) is 0.45 $Ω$$μ$m$^{2}$, as well as the perfect spin filtering and negative differential resistance effects. More intriguingly, TMR (TER) can be further enhanced to 34000\% (380\%) by applying an external bias voltage (0.1 V), while RA can be reduced to 0.16 $Ω$$μ$m$^{2}$ under the influence of biaxial stress (-3\%). Our proposed concept of designing vdW-MFTJs using intrinsic multiferroic materials points towards new avenues in experimental exploration.

cond-mat.mtrl-sci↗

arXiv2022

Online decentralized tracking for nonlinear time-varying optimal power flow of coupled transmission-distribution grids

The coordinated alternating current optimal power flow (ACOPF) for coupled transmission-distribution grids has become crucial to handle problems related to high penetration of renewable energy sources (RESs). However, obtaining all system details and solving ACOPF centrally is not feasible because of privacy concerns. Intermittent RESs and uncontrollable loads can swiftly change the operating condition of the power grid. Existing decentralized optimization methods can seldom track the optimal solutions of time-varying ACOPFs. Here, we propose an online decentralized optimization method to track the time-varying ACOPF of coupled transmission-distribution grids. First, the time-varying ACOPF problem is converted to a dynamic system based on Karush-Kuhn-Tucker conditions from the control perspective. Second, a prediction term denoted by the partial derivative with respect to time is developed to improve the tracking accuracy of the dynamic system. Third, a decentralized implementation for solving the dynamic system is designed based on only a few information exchanges with respect to boundary variables. Moreover, the proposed algorithm can be used to directly address nonlinear power flow equations without relying on convex relaxations or linearization techniques. Numerical test results reveal the effectiveness and fast-tracking performance of the proposed algorithm.

math.OC↗

arXiv2021

An Accelerated Stackelberg Game Approach for Distributed Energy Resource Aggregator participating in Energy and Reserve Markets Considering Security Check

With increasing distributed energy resoures (DERs) integration, the strategic behavior of a DER aggregator in electricity markets will significantly affect the secure operation of the distribution system. In this paper, the interactions among the DER aggregator, energy and reserve markets, and distribution system are investigated through a single-leader-multi-follower Stackelberg game model with the DER aggregator as the leader and the independent system operator and distribution system operator as the followers. To guarantee the operation security of the distribution system, security check problems under three different scenarios are involved in the follower level, which is linearized using a mixed-integer linearized power flow model. Then, using the strong duality theorem, the proposed model is converted into a bi-level mixed-integer linear (BMILP) programming model with only mixed-integer linear follower-level problems. Next, an accelerated relaxation-based bi-level reformulation and decomposition algorithm is proposed to solve the BMILP problem. Finally, case studies are carried out on a constructed integrated transmission and distribution (T&D) system and a practical integrated T&D system to verify the effectiveness of the proposed model and algorithm. The simulation results indicate that the available downward reserve of the DER aggregator will decrease with the security limitation of the distribution system.

eess.SY↗