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Diluted Oxide Interfaces with Tunable Ground States
摘要： The metallic interface between two oxide insulators, such as LaAlO3/SrTiO3 (LAO/STO), provides new opportunities for electronics and spintronics. However, due to the presence of multiple orbital populations, tailoring the interfacial properties such as the ground state and metal-insulator transitions remains challenging. Here, an unforeseen tunability of the phase diagram of LAO/STO is reported by alloying LAO with a ferromagnetic LaMnO3 insulator without forming lattice disorder and at the same time without changing the polarity of the system. By increasing the Mn-doping level, x, of LaAl1?xMnxO3/STO (0 ≤ x ≤ 1), the interface undergoes a Lifshitz transition at x = 0.225 across a critical carrier density of nc = 2.8 × 1013 cm?2, where a peak TSC ≈255 mK of superconducting transition temperature is observed. Moreover, the LaAl1?xMnxO3 turns ferromagnetic at x ≥ 0.25. Remarkably, at x = 0.3, where the metallic interface is populated by only dxy electrons and just before it becomes insulating, a same device with both signatures of superconductivity and clear anomalous Hall effect (7.6 × 1012 cm?2 < ns ≤ 1.1 × 1013 cm?2) is achieved reproducibly. This provides a unique and effective way to tailor oxide interfaces for designing on-demand electronic and spintronic devices.
关键词： anomalous Hall effect,2D electron liquid,oxide interfaces,superconductivity,metal-insulator transitions
更新于2025-09-23 15:23:52
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Terahertz Emission From an Exchange-Coupled Synthetic Antiferromagnet
摘要： We report on terahertz emission from Fe-Mn-Pt/Ru/Fe-Mn-Pt and Pt/Co-Fe-B/Ru/Co-Fe-B/Pt synthetic antiferromagnet (SAF) structures upon irradiation by a femtosecond laser; the former is via the anomalous Hall effect, whereas the latter is through the inverse spin Hall effect. The antiparallel alignment of the two ferromagnetic layers leads to a terahertz emission peak amplitude that is almost double that of a corresponding single-layer or bilayer emitter with the same equivalent thickness. In addition, we demonstrate by both simulation and experiment that terahertz emission provides a powerful tool to probe the magnetization reversal processes of individual ferromagnetic layers in a SAF structure, as the terahertz signal is proportional to the vector difference (M1 ? M2) of the magnetizations of the two ferromagnetic layers.
关键词： anomalous Hall effect,synthetic antiferromagnet,terahertz emission,magnetization reversal,inverse spin Hall effect
更新于2025-09-23 15:21:01
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Photoinduced tunable anomalous Hall and Nernst effects in tilted Weyl semimetals using Floquet theory
摘要： In this paper, we discuss the effect of a periodically driving circularly polarized laser beam in the high-frequency limit, on the band structure and thermal transport properties of type-I and type-II Weyl semimetals (WSMs). We develop the notion of an effective Fermi surface stemming from the time-averaged Floquet Hamiltonian and discuss its effects on the steady-state occupation numbers of electrons and holes in the linearized model. In order to compute the transport coef?cients averaged over a period of the incident laser source, we employ the Kubo formalism for Floquet states and show that the Kubo formula for the conductivity tensor retains its well-known form with the difference that the eigenstates and energies are replaced by the Floquet states and their quasienergies. We ?nd that for type-I WSMs the anomalous thermal Hall conductivity grows quadratically with the amplitude A0 of the U(1) gauge ?eld for low tilt, while the Nernst conductivity remains unaffected. For type-II WSMs, the Hall conductivity decreases nonlinearly with A0 due to the contribution from the physical momentum cutoff, required to keep ?nite electron and hole pocket sizes, and the Nernst conductivity falls off logarithmically with A2 0. These results may serve as a diagnostic for material characterization and transport parameter tunability in WSMs, which are currently the subject of a wide range of experiments.
关键词： Nernst effect,Floquet theory,anomalous Hall effect,thermal transport,Weyl semimetals
更新于2025-09-23 15:21:01
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Comparing the anomalous Hall effect and the magneto-optical Kerr effect through antiferromagnetic phase transitions in Mn <sub/>3</sub> Sn
摘要： In the non-collinear antiferromagnet Mn3Sn, we compare simultaneous measurements of the anomalous Hall effect (AHE) and the magneto-optical Kerr effect (MOKE) through two magnetic phase transitions: the high-temperature paramagnetic/antiferromagnetic (AF) phase transition at the N(cid:2)eel temperature (TN (cid:2) 420 K) and a lower-temperature incommensurate magnetic ordering at T1 (cid:2) 270 K. While both the AHE and MOKE are sensitive to the same underlying symmetries of the AF non-collinear spin order, we ?nd that the transition temperatures measured by these two techniques unexpectedly differ by approximately 10 K. Moreover, the applied magnetic ?eld at which the AF order reverses is signi?cantly larger when measured by MOKE than when measured by AHE. These results point to a difference between the bulk and surface magnetic properties of Mn3Sn.
关键词： antiferromagnetic phase transitions,anomalous Hall effect,magneto-optical Kerr effect,Mn3Sn
更新于2025-09-19 17:15:36
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Prediction of high-temperature Chern insulator with half-metallic edge states in asymmetry-functionalized stanene
摘要： A great obstacle for the practical applications of the quantum anomalous Hall (QAH) effect is the lack of suitable two-dimensional (2D) materials with a sizable nontrivial band gap, high Curie temperature, and high carrier mobility. Based on first-principles calculations, here, we propose the realizations of these intriguing properties in asymmetry-functionalized 2D SnHN and SnOH lattices. Spin-polarized band structures reveal that SnOH monolayer exhibits a spin gapless semiconductor (SGS) feature, whereas SnNH is converted to SGS under compressive strain. The Curie temperature of SnOH reaches 266 K, as predicted by Monte Carlo simulation, and it is comparable to the room temperature. When the spin and orbital degrees of freedom are allowed to couple, both systems become large-gap QAH insulators with fully spin-polarized half-metallic edge states and higher Fermi velocity of 4.9 × 10^5 m s^?1. These results pave a new way for designing topological field transistors in group-IV honeycomb lattices.
关键词： topological,stanene,quantum anomalous Hall effect,spin gapless semiconductor,Chern insulator
更新于2025-09-19 17:15:36
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Nanomachining-enabled strain manipulation of magnetic anisotropy in the free-standing GaMnAs nanostructures
摘要： Strain perturbs atomic ordering in solids, with far-reaching consequences from an increased carrier mobility to localization in Si, stabilization of electric dipoles and nanomechanical transistor action in oxides, to the manipulation of spins without applying magnetic fields in n-GaAs. In GaMnAs, a carrier-mediated ferromagnetic semiconductor, relativistic spin-orbit interactions – highly strain-dependent magnetic interactions – play a crucial role in determining the magnetic anisotropy (MA) and anisotropic magnetoresistance (AMR). Strain modifies the MA and AMR in a nanomachined GaMnAs structure as measured by the anomalous Hall effect (AHE) and the planar Hall effect (PHE). Here, we report an MA modification by strain relaxation in an isolated GaMnAs Hall bar structure and by applying a range of local strains via fabricating asymmetrically mechanically buckled GaMnAs micro-Hall bar structures. in the AHe and pHe measurements, we observe a reduction in the in-plane MA and an enhancement in the out-of-plane MA as the compressive strain due to the lattice mismatch relaxes in the suspended structure. The functionality of such mechanical manipulation, as well as the two-level mechanical state and the corresponding AHe responses, is demonstrated by a fully scalable binary mechanical memory element in a GaMnAs single Hall cross structure.
关键词： strain,GaMnAs,magnetic anisotropy,planar Hall effect,anomalous Hall effect
更新于2025-09-12 10:27:22
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Giant tunable nonreciprocity of light in Weyl semimetals
摘要： The propagation of light in Weyl semimetal films is analyzed. The magnetic family of these materials is known by anomalous Hall effect, which, being enhanced by the large Berry curvature, allows one to create strong gyrotropic and nonreciprocity effects without external magnetic field. The existence of nonreciprocal waveguide electromagnetic modes in ferromagnetic Weyl semimetal films in the Voigt configuration is predicted. Thanks to the strong dielectric response caused by the gapless Weyl spectrum and the large Berry curvature, ferromagnetic Weyl semimetals combine the best waveguide properties of magnetic dielectrics or semiconductors with strong anomalous Hall effect in ferromagnets. The magnitude of the nonreciprocity depends both on the internal Weyl semimetal properties, the separation of Weyl nodes, and the external factor, the optical contrast between the media surrounding the film. By tuning the Fermi level in Weyl semimetals, one can vary the operation frequencies of the waveguide modes in THz and mid-IR ranges. Our findings pave the way to the design of compact, tunable, and effective nonreciprocal optical elements.
关键词： Weyl semimetals,optical elements,anomalous Hall effect,nonreciprocity,waveguide modes
更新于2025-09-11 14:15:04
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[IEEE 2018 Conference on Precision Electromagnetic Measurements (CPEM 2018) - Paris, France (2018.7.8-2018.7.13)] 2018 Conference on Precision Electromagnetic Measurements (CPEM 2018) - Zero-Field Quantized Anomalous Hall Resistance of (Bi,Sb)2 Te3
摘要： In the quantum anomalous Hall effect, the edge states of a ferromagnetically doped topological insulator exhibit quantized Hall resistance and dissipationless transport at zero magnetic field. Here, we present a measurement of the resistance quantization of V-doped (Bi,Sb)2Te3 devices in zero external magnetic field. For the deviation of the quantized anomalous Hall resistance from RK we determined a value of 0.17 ± 0.25 μΩ/Ω. This is a step towards realization of a practical zero-field quantum resistance standard which in combination with the Josephson effect could provide the universal quantum units standard in the future.
关键词： quantum anomalous Hall effect,quantum resistance standards,Quantum Hall effect
更新于2025-09-10 09:29:36
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Penta-AlN2 monolayer: A ferromagnetic insulator
摘要： A ferromagnetic insulating behavior is necessary to realize quantum anomalous Hall effect. Here we study, using first-principles calculations and a Monte Carlo simulation, the electronic structure and magnetism of AlN2 monolayer. Our results show that the AlN2 monolayer has a ferromagnetic insulating behavior. By using the crystal field analysis, we find that the axes of the neighboring N2 dimers are perpendicular, and the superexchange between them accounts for the ferromagnetic (FM) order in the AlN2 monolayer. We also carried out a Monte Carlo simulation, which shows that the AlN2 monolayer remains FM with Curie temperature (Tc) ~ 22 K. Moreover, the tensile strain would make a stronger overlap between the neighboring N2 dimers, and steadily enhances the FM stability. As a result, the Tc can be increased with the tensile strain.
关键词： tensile strain,ferromagnetic insulator,AlN2 monolayer,superexchange,quantum anomalous Hall effect
更新于2025-09-10 09:29:36
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Anomalous Hall-like transverse magnetoresistance in Au thin films on Y <sub/>3</sub> Fe <sub/>5</sub> O <sub/>12</sub>
摘要： Anomalous Hall-like signals in platinum in contact with magnetic insulators are common observations that could be explained by either proximity magnetization or spin Hall magnetoresistance (SMR). In this work, longitudinal and transverse magnetoresistances are measured in a pure gold thin film on the ferrimagnetic insulator Y3Fe5O12 (Yttrium Iron Garnet, YIG). We show that both the longitudinal and transverse magnetoresistances have quantitatively consistent scaling in YIG/Au and in a YIG/Pt reference system when applying the SMR framework. No contribution of an anomalous Hall effect due to the magnetic proximity effect is evident.
关键词： gold thin films,Anomalous Hall effect,Y3Fe5O12,proximity magnetization,spin Hall magnetoresistance
更新于2025-09-09 09:28:46