arXiv subjects

Zhi-Min Liao

Publications and source records attributed to Zhi-Min Liao.

At least 19 recordsLinked to original sources

arXiv2026

Observation of Kondo Effect in Rhombohedral Graphene Superlattices

Kondo effect in strongly correlated systems arises from the antiferromagnetic coupling between itinerant conduction electrons and localized magnetic moments, giving rise to a variety of exotic quantum phenomena. Two-dimensional moiré superlattice systems provide a highly tunable platform featuring topological flat bands, where Wannier orbitals are spatially confined by the periodic moiré potential and serve as localized magnetic moments, enabling the observable Kondo effect. Here we experimentally demonstrate Kondo interactions in hexalayer rhombohedral graphene moiré superlattices through magneto-transport and temperature-dependent measurements. With increasing magnetic field, the magnetoresistance exhibits an increase-decrease transition across a critical field B_c, while the Hall resistance R_xy undergoes a sign reversal near B_c. Moreover, as temperature decreases, the longitudinal resistance R_xx first increases logarithmically and then decreases following a T^2 behavior, indicating a transition to heavy fermion liquid. These behaviors can be consistently explained by the breakdown of Kondo singlets induced by either magnetic field or temperature, which liberates carriers previously bound to localized moments, thereby enhancing conductivity and altering the dominant carrier type. Furthermore, our results demonstrate that the Kondo interaction can be continuously tuned by both carrier density n and displacement electric field D, and suggest the emergence of a Kondo insulating state. Our findings provide deep insight into the Kondo effect in moiré engineered flat-band systems, paving the path for exploring exotic correlated quantum phases.

cond-mat.mes-hall↗

arXiv2026

Oxidation-induced ultrafast spin-to-orbital conversion at heavy-metal interfaces

Oxidation engineering provides a route to control orbital degrees of freedom, yet its role in spin-to-orbital conversion remains largely unexplored. Here, we report an efficient spin-to-orbital conversion mechanism driven by interfacial oxidation at heavy-metal interfaces. In W/Co/SiO2 heterostructures, terahertz emission exhibits a time delay that scales linearly with the W thickness, identifying orbital-current transport as the dominant origin. The emission amplitude is approximately three times larger than that of Co/Pt bilayers, indicating highly efficient conversion from spin to orbital angular momentum. Systematic variation of Co thickness, stoichiometry, and interface configuration reveals that the effect originates from oxidation of the W layer at the W/Co interface, which modulates the interfacial orbital texture. We further show that this mechanism is generic across different heavy metals and scales with their spin-orbit coupling strength. These results establish oxidation as an effective handle to engineer spin-to-orbital conversion and provide a general route toward orbitronic terahertz emitters.

cond-mat.mes-hall↗

arXiv2026

Gate-tunable anisotropic Josephson diode effect in topological Dirac semimetal Cd$_3$As$_2$ nanowires

The intrinsic Josephson diode effect (JDE) has recently attracted considerable attention due to its sensitivity to broken symmetries in Josephson junctions, offering a powerful probe for uncovering hidden symmetry-breaking mechanisms in materials. The presence of higher-harmonic components in the current-phase relation, together with spin-orbital coupling, makes topological materials ideal platforms to explore this effect. In this work, we present a systematic study of the JDE in type-I topological Dirac semimetal Cd$_3$As$_2$ nanowire-based Josephson junctions. We observe a pronounced gate-tunable and highly anisotropic diode response under different magnetic-field orientations. By developing a comprehensive phenomenological model, we capture the angular dependence of the diode effect and, through temperature-dependent measurements, disentangle the respective contributions from bulk and topological surface states. Notably, anomalies in the temperature dependence of the diode efficiency reveal the coexistence of multiple transport channels, highlighting the Josephson diode effect as a sensitive probe of hidden topological superconducting states.

cond-mat.mes-hall↗

arXiv2025

Radio-Frequency Quantum Rectification in Kagome Superconductor CsV3Sb5

Rectification of electromagnetic fields into direct current (DC) is pivotal for energy harvesting, wireless charging, and next-generation communication technologies. The superconducting diode effect, which exploits the nonreciprocal transport of dissipationless superconducting currents, offers ultra-low power consumption and high rectification ratios. Combining the superconducting diode effect with the AC Josephson effect holds promise for converting radio-frequency (rf) irradiation into a quantized DC output. However, experimental realization has been hindered by challenges in achieving the necessary symmetry breaking and fabricating high-performance Josephson junctions. Here we demonstrate the quantum rectification in kagome superconductor CsV3Sb5, which hosts emergent Josephson effects and a zero-field Josephson diode. Under rf irradiation, a DC voltage emerges without applied bias, scaling linearly with frequency as V = hf/2e, where h is Planck's constant, f is the microwave frequency, and e is the electron charge. Furthermore, the rectified voltage exhibits quantized steps with increasing rf power, consistent with Shapiro step quantization. Our work establishes CsV3Sb5 as a versatile platform for wireless quantum power supplies and charging, and underscores the intertwined order parameters as a promising pathway for precise quantum matter control.

cond-mat.supr-con↗

arXiv2025

Magnetic Field Induced Quantum Metric Dipole in Dirac Semimetal Cd3As2

The quantum geometry, comprising Berry curvature and quantum metric, plays a fundamental role in governing electron transport phenomena in solids. Recent studies show that the quantum metric dipole drives scattering-free nonlinear Hall effect in topological antiferromagnets, prompting the questions of whether this effect can occur in nonmagnetic systems and be externally tuned by a magnetic field. Our work addresses these frontiers by demonstrating that the quantum metric dipole is actively tuned by an external magnetic field to generate a time-reversal-odd nonlinear Hall response in a nonmagnetic topological Dirac semimetal Cd3As2. Alongside the well-known chiral-anomaly-induced negative longitudinal magnetoresistance, an exotic nonlinear planar Hall effect emerges with increasing magnetic field. Careful scaling analysis indicates that this nonlinear planar Hall effect is controlled by the magnetic-field-modulated quantum metric dipole. Constructing a k.p effective model of the Dirac bands under Zeeman and orbital coupling, we derive the evolution of the quantum metric dipole as a function of the magnetic field, providing a comprehensive explanation of the experimental results. Our results establish a band-structure-based strategy for engineering nonlinear magnetotransport in nonmagnetic materials via the quantum metric dipole, opening a pathway toward magnetic-field-tunable nonlinear quantum devices.

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arXiv2025

From surface Fermi arcs to Fermi loops in the Dirac semimetal Cd3As2

Arc-like topological surface states, i.e., surface Fermi arcs, have long been recognized as the hallmark of Dirac semimetals. However, recent theories suggest that the surface Fermi arcs could evolve into closed Fermi loops, akin to surface states in topological insulators, while preserving the bulk Dirac semimetal phase. Here we experimentally reveal the evolution of Fermi arcs to Fermi loops in the surface-modified Dirac semimetal Cd3As2 nanoplate through gate voltage-dependent spin transport and quantum oscillation measurements. Surface modification, achieved by heavy metal atom deposition and water molecule adsorption, leads to an increase in the current-induced spin polarization at higher gate voltages, contrasting with the decrease observed in the pristine nanoplate. We also observe surface Shubnikov-de Haas oscillations with frequencies that scale linearly with gate voltage, aligning with a Fermi loop scenario. These findings indicate a transition from Fermi arcs to a closed Fermi loop in the surface-modified Cd3As2 nanoplate, consistent with the theoretically predicted fragile topological nature of Cd3As2. Our research offers profound insights into the transitions among these subtle topological states in Dirac semimetals, paving the way for manipulating topological surface states for high-performance spintronic devices.

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arXiv2025

Charge density wave modulated third-order nonlinear Hall effect in 1$T$-VSe$_2$ nanosheets

We report the observation of a pronounced third-order nonlinear Hall effect (NLHE) in 1$T$-phase VSe$_2$ nanosheets, synthesized using chemical vapor deposition (CVD). The nanosheets exhibit a charge density wave (CDW) transition at $\sim$77 K. Detailed angle-resolved and temperature-dependent measurements reveal a strong cubic relationship between the third-harmonic Hall voltage $V_{3ω}^\perp$ and the bias current $I_ω$, persisting up to room temperature. Notably, the third-order NLHE demonstrates a twofold angular dependence and significant enhancement below the CDW transition temperature, indicative of threefold symmetry breaking in the CDW phase. Scaling analysis suggests that the intrinsic contribution from the Berry connection polarizability tensor is substantially increased in the CDW phase, while extrinsic effects dominate at higher temperatures. Our findings highlight the critical role of CDW-induced symmetry breaking in modulating quantum geometric properties and nonlinear transport phenomena in VSe$_2$, paving the way for future explorations in low-dimensional quantum materials.

cond-mat.mes-hall↗

arXiv2025

Current-induced magnetoresistance hysteresis in the kagome superconductor CsV$_3$Sb$_5$

We report the observation of current-modulated magnetoresistance hysteresis below the superconducting transition temperature in the kagome superconductor CsV$_3$Sb$_5$. This highly tunable hysteresis behavior is confined to the superconducting state and vanishes when superconductivity is fully suppressed, directly linking magnetoresistance hysteresis to the superconducting order in CsV$_3$Sb$_5$. Additionally, the superconducting diode effect driven by a small magnetic field is observed, indicating the enhanced electronic magnetochiral anisotropy by the chiral domain-wall scattering. Our findings position CsV$_3$Sb$_5$ as a promising platform for exploring nontrivial physical phenomena, including unconventional pairing mechanisms and topological superconductivity.

cond-mat.supr-con↗

arXiv2025

Engineering nonlinear Hall effect in bilayer graphene/black phosphorus heterostructures

Two-dimensional van der Waals materials offer a highly tunable platform for generating emergent quantum phenomena through symmetry breaking. Stacking-induced symmetry breaking at interfaces provides an effective method to modulate their electronic properties for functional devices. Here, we strategically stack bilayer graphene with black phosphorus, a low-symmetry semiconductor, to break the symmetries and induce the nonlinear Hall effect (NLHE) that can persist up to room temperature. Intriguingly, it is found the NLHE undergoes sign reversals by varying the electrical displacement field under fixed carrier density. The scaling analysis reveals that the sign reversal of the NLHE is contributed from both the Berry curvature dipole (BCD) and extrinsic scatterings. The displacement field-induced sign reversal of the BCD indicates asymmetric distributions of Berry curvature hot spots across different Fermi pockets in bilayer graphene. Our findings suggest that symmetry engineering of van der Waals heterostructures is promising for room-temperature applications based on nonlinear quantum devices, such as high-frequency rectifiers and wireless charging.

cond-mat.mes-hall↗

arXiv2025

Giant Third-Order Nonlinearity Induced by the Quantum Metric Quadrupole in Few-Layer WTe2

The quantum geometric properties of topological materials underpin many exotic physical phenomena and applications. Quantum nonlinearity has emerged as a powerful probe for revealing these properties. The Berry curvature dipole in nonmagnetic materials and the quantum metric dipole in antiferromagnets have been explored by studying the second-order nonlinear Hall effect. Although the quadrupole moment of the quantum geometric tensor is theoretically predicted to induce higher-order quantum nonlinearity, the quantum metric quadrupole remains experimentally unexplored. Here, we report the quantum metric quadrupole induced third-order nonlinear longitudinal electrical response in few-layer WTe2, persisting up to room temperature. Angle-resolved third-harmonic current-voltage characteristics are found consistent with the intrinsic crystal symmetry of WTe2. Through temperature variation and scaling analysis, we identify the quantum metric quadrupole as the physical origin of the observed third-order longitudinal nonlinearity. Additionally, we determine the angle dependence of the quantum metric quadrupole, establishing third-order nonlinearity as an efficient method for revealing the quantum metric structure.

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arXiv2024

Nonlinear Valley and Spin Valves in Bilayer Graphene

Nonlinear transport plays a vital role in probing the quantum geometry of Bloch electrons, valley chirality, and carrier scattering mechanisms. The nonlinear Hall effect, characterized by a nonlinear scaling of Hall voltage with longitudinal current, has been explored to reveal the Berry curvature and quantum metric related physics. In this work, we extend the study of nonlinear transport to spin and valley degrees of freedom. Using bilayer graphene devices with Fe3GeTe2 contacts, we observe a second-order nonlinear spin current exhibiting spin valve-like behaviors. By tracking magnetic moment precession under an in-plane magnetic field, we identify a significantly enhanced critical magnetic field required for in-plane rotation, suggesting out-of-plane valley polarization induced by ferromagnetic proximity. These findings offer deep insights into the interplay of valley and spin in second-order nonlinear transport, opening avenues for promising device applications.

cond-mat.mes-hall↗

arXiv2024

Orbital anomalous Hall effect in the few-layer Weyl semimetal TaIrTe4

We report on the observation of the linear anomalous Hall effect (AHE) in the nonmagnetic Weyl semimetal TaIrTe4. This is achieved by applying a direct current Idc and an alternating current Iac (Iac<<Idc) in TaIrTe4, where the former induces time-reversal symmetry breaking and the latter probes the triggered AHE. The anomalous Hall resistance VacH/Iac shows a linear dependence on Idc and changes sign with the polarity of Idc. In temperature-dependent measurements, VacH/Iac also experiences a sign reversal at 100 K, consistent with the temperature-dependent nonlinear Hall effect (NLHE). Furthermore, in measurements involving only dc transport, the dc Hall voltage exhibits a quadratic relationship with Idc. When the Idc direction is reversed, the Hall resistance changes sign, demonstrating a colossal nonreciprocal Hall effect (NRHE). Our theoretical calculations suggest that the observed linear AHE, NLHE, and NRHE all dominantly originate from the current-induced orbital magnetization compared to the minor spin contribution. This work provides deep insights into the orbital magnetoelectric effect and nonlinear Hall response, promising precise electric control of out-of-plane polarized orbit flow.

cond-mat.mes-hall↗

arXiv2024

Nonlinear spin and orbital Edelstein effect in WTe2

In materials with spin-momentum locked spin textures, such as Rashba states and topological surface states, the current-induced shift of the Fermi contour in the k space leads to spin polarization, known as the Edelstein effect, which depends linearly on the applied current. However, its nonlinear counterpart has not yet been discovered. Here, we report the observation of the nonlinear Edelstein effect in few-layer WTe2. Under a current bias, an out-of-plane magnetization is induced in WTe2, which is electrically probed using an Fe3GeTe2 electrode, a van der Waals ferromagnet with perpendicular magnetic anisotropy. Notably, with an applied ac at frequency ω, an induced magnetization with second-harmonic response at frequency 2ω is observed, and its magnitude demonstrates a quadratic dependence on the applied current, characteristic of the nonlinear Edelstein effect. This phenomenon is well explained by the current-induced orbital magnetization via the Berry connection polarizability tensors in WTe2. The orbital degree of freedom plays the primary role in the observed nonlinear Edelstein effect, that is, the nonlinear orbital Edelstein effect. This can, in turn, give rise to a nonlinear spin Edelstein effect through spin-orbit coupling.

cond-mat.mes-hall↗

arXiv2024

Resistive anisotropy in the charge density wave phase of Kagome superconductor CsV3Sb5 thin films

We investigate the resistive anisotropy in CsV3Sb5 thin films within the charge density wave phase. Using a device structure with twelve electrodes symmetrically distributed in a circular shape, we measure the resistivity anisotropy by varying the current direction. A twofold resistivity anisotropy modulated by temperature is found, which is fully consistent with the electronic nematicity in CsV3Sb5, that is, the spontaneous rotational symmetry breaking by electronic degree of freedom. Additionally, the resistivity anisotropy also shows modest changes by applying magnetic fields, implying the possible chiral charge orders with time-reversal symmetry breaking. These findings provide deep insights into the correlated electronic states in Kagome materials and highlight the unique properties of CsV3Sb5 in the two-dimensional regime.

cond-mat.supr-con↗

arXiv2024

Room-temperature van der Waals magnetoresistive memories with data writing by orbital current in the Weyl semimetal TaIrTe4

Current-induced out of plane magnetization has been utilized for field-free switching of ferromagnets with perpendicular magnetic anisotropy. Identifying systems capable of energy-efficiently converting charge currents into out of plane orbit- or spin-polarized currents is crucial for advancing magnetic memory technologies. Here we introduce the Berry curvature dipole as a key evaluation factor, directly measurable through nonlinear Hall effects. In the Weyl semimetal TaIrTe4 used in our experiments, applying a current parallel to the Berry curvature dipole results in out of plane orbital magnetization, which governs the field-free perpendicular magnetization switching in TaIrTe4/Fe3GaTe2 heterostructures. Notably, all-electric control of van der Waals magnetoresistive memory at room temperature has been achieved with a low critical current density 2x10^6A/cm2 for data writing. Our findings reveal the connection between nonlinear Hall effects and field-free magnetization switching, highlighting the potential of the Berry curvature dipole in advancing orbitronics.

cond-mat.mes-hall↗

arXiv2024

Facilitating field-free perpendicular magnetization switching with a Berry curvature dipole in a Weyl semimetal

We report the synergy between orbital and spin-orbit torques in WTe2/Fe3GeTe2 heterostructures characterized by a Berry curvature dipole. By applying a current along the a axis in WTe2, we detect an out-of-plane magnetization in the system, which we attribute to nonequilibrium orbital magnetization linked to the Berry curvature dipole based on first-principles calculations, manifesting as the orbital Edelstein effect. This effect generates orbital torques that enable field-free perpendicular magnetization switching. Furthermore, by applying a relatively small current along the a axis and a pulsed current along the b axis in WTe2, we demonstrate controllable field-free magnetization switching of the adjacent Fe3GeTe2 layer, independently manipulating the orbital and spin-orbit torques. Our findings not only enhance the understanding of the collaborative dynamics between these torques but also suggest potential applications in magnetoresistive random-access memory.

cond-mat.mes-hall↗

arXiv2023

Room-temperature orbit-transfer torque enabling van der Waals magnetoresistive memories

The nonvolatile magnetoresistive random access memory (MRAM) is believed to facilitate emerging applications, such as in memory computing, neuromorphic computing and stochastic computing. Two dimensional (2D) materials and their van der Waals heterostructures promote the development of MRAM technology, due to their atomically smooth interfaces and tunable physical properties. Here we report the all-2D magnetoresistive memories featuring all electrical data reading and writing at room temperature based on WTe2/Fe3GaTe2/BN/Fe3GaTe2 heterostructures. The data reading process relies on the tunnel magnetoresistance of Fe3GaTe2/BN/Fe3GaTe2. The data writing is achieved through current induced polarization of orbital magnetic moments in WTe2, which exert torques on Fe3GaTe2, known as the orbit transfer torque (OTT) effect. In contrast to the conventional reliance on spin moments in spin transfer torque and spin orbit torque, the OTT effect leverages the natural out of plane orbital moments, facilitating field-free perpendicular magnetization switching through interface currents. Our results indicate that the emerging OTT MRAM is promising for low power, high performance memory applications.

cond-mat.mes-hall↗

arXiv2023

Gate-Tunable Berry Curvature Dipole Polarizability in Dirac Semimetal Cd3As2

We reveal the gate-tunable Berry curvature dipole polarizability in Dirac semimetal Cd3As2 nanoplates through measurements of the third-order nonlinear Hall effect. Under an applied electric field, the Berry curvature exhibits an asymmetric distribution, forming a field-induced Berry curvature dipole, resulting in a measurable third-order Hall voltage with a cubic relationship to the longitudinal electric field. Notably, the magnitude and polarity of this third-order nonlinear Hall effect can be effectively modulated by gate voltages. Furthermore, our scaling relation analysis demonstrates that the sign of the Berry curvature dipole polarizability changes when tuning the Fermi level across the Dirac point, in agreement with theoretical calculations. The results highlight the gate control of nonlinear quantum transport in Dirac semimetals, paving the way for promising advancements in topological electronics.

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