arXiv subjects

Ziang Meng

Publications and source records attributed to Ziang Meng.

16 recordsLinked to original sources

arXiv2026

Saturated and Anisotropic Magnetostriction in an Altermagnet

Magnetostriction, a fundamental phenomenon bridging magnetism and mechanics, has enabled a broad spectrum of applications. For almost two centuries, it has been mainly investigated for ferromagnets. Regarding the magnetostriction of antiferromagnets (AFMs), limitedly known examples for both conventional collinear AFMs and noncollinear AFMs predominantly exhibit non-saturating magnetic-field dependence. Herein, we report an easily saturated magnetostriction effect in a prototypical altermagnet - MnTe, which is an emerging class of collinear AFMs with special crystal symmetries. For high-quality MnTe single crystals, the magnetostriction saturates under a moderate field of ~0.7 T with an intriguing two-fold-symmetry anisotropy. First-principles calculations reveal that the saturated and anisotropic magnetostriction originates from symmetry-allowed coupling between elastic strain and its N\'eel order parameter. These findings break the traditional wisdom on antiferromagnetic magnetostriction.

cond-mat.mtrl-sci↗

arXiv2026

Giant Room-Temperature Third-Order Electrical Transport in a Thin-Film Altermagnet Candidate

Quantum geometry, a quantum mechanical quantity comprised of Berry curvature and quantum metric, describes the geometric structure of the electronic bands in solids. The correlation between nontrivial quantum geometry and quantum materials leads to new findings in condensed matter systems. Here we demonstrate that altermagnets, with spontaneously broken time-reversal (T)- half-lattice-translation and parity-time symmetry, host both T-odd and T-even quantum geometric quantities that simultaneously manifest themselves despite the vanishing net magnetization. Consequently, giant room-temperature third-order electrical transport responses with sizable quantum geometric contributions are observed in (101)-oriented RuO2 thin films, an altermagnetic candidate; in particular, the third-order Hall effect is intimately correlated with altermagnetic order and can serve as a promising tool for detecting the Neel vector. Our work not only supports the existence of altermagnetism in 8-nm-thick RuO2 thin films, but also shows altermagnets as a versatile platform for exploring quantum geometry and constructing quantum electronic and spintronic devices.

cond-mat.mes-hall↗

arXiv2026

Bulk OsO2 Single Crystals: Superior Catalysts for Water Oxidation

Although rutile RuO2 has been a well-known and almost the best oxygen evolution reaction (OER) catalyst, the OER properties for the similar rutile oxide OsO2 with the same group element with Ru have been unknown, mainly due to long-standing synthesis difficulties. In this work, we report the successful synthesis of high-quality OsO2 single crystals, and the ground micrometer-size single crystals are chemically stable in alkaline solutions and exhibit robust OER performance. In sharp contrast, OsO2 nanopowder reacts quickly with KOH solutions and cannot work for OER. Compared with commercial RuO2 nanopowder, the OsO2 single crystals show comparable catalytic current densities, remarkably lower overpotentials at high current densities and better stability. These findings question the universal applicability of nanoscaling and highlight crystal integrity as a key descriptor for achieving stable and efficient OER electrocatalysis.

cond-mat.mtrl-sci↗

arXiv2026

Pressure-Induced Metal-Insulator and Paramagnet-Altermagnet Transitions in Rutile OsO2 Single Crystals

Altermagnets with compensated spin structures and nonrelativistic spin splitting have emerged as a new class of magnetic materials. Rutile OsO2 has been theoretically predicted to be altermagnetic, but experimental studies have been limited by synthesis challenges. We have succeeded in synthesizing high-quality single crystals of rutile OsO2. Electrical transport studies reveal that OsO2 is highly conductive and exhibits clear Fermi liquid behavior, indicating strong electron-electron scattering. Magnetic measurements show that the crystals are isotropically paramagnetic. Density-functional theory calculations indicate that bulk OsO2 is semimetallic with coexisting electron and hole pockets, with its magnetic ground state strongly dependent on the on-site Coulomb correlation U. Angle-resolved photoemission spectroscopy studies unveil that the bulk bands do not yet show altermagnetic spin splitting. Interestingly, resistivity is rather pressure sensitive: at 44 GPa, a clear metal-insulator transition occurs. Hybrid functional calculations reveal that applying pressure significantly increases the Hubbard U value, driving a phase transition from a paramagnetic metal to an altermagnetic metal, and eventually to an altermagnetic insulator. These findings suggest that tuning external pressure effectively modulates the magnetic ground state of OsO2, providing a pathway to realize altermagnetism in this material.

cond-mat.mes-hall↗

arXiv2026

Observation of Orbit-Orbit Torques: Highly Efficient Torques on Orbital Moments Induced by Orbital Currents

We study the current-induced torques in bilayers composed of a light 3d metal, chromium, and a rare-earth ferromagnet with finite orbital moments, terbium, utilizing second-harmonic Hall-response measurements. The dampinglike torque efficiency of chromium is found to be positive and reaches ~3.66 in this system, in sharp contrast to the negative and subtle dampinglike torque efficiency in general Cr/ferromagnet heterostructures with quenched orbital moment. We suggest that the orbital currents generated by the orbital Hall effect in Cr can be injected into Tb with negligible loss at the interface and then efficiently interact with the orbital moments. We term such an exotic effect as the orbit-orbit torque (OOT). Our work implies that orbital currents could be harnessed to manipulate the orbital magnetization of materials, which would advance the development of orbitronics.

cond-mat.mes-hall↗

arXiv2025

Electric-Field-Controlled Altermagnetic Transition for Neuromorphic Computing

Altermagnets represent a novel magnetic phase with transformative potential for ultrafast spintronics, yet efficient control of their magnetic states remains challenging. We demonstrate an ultra-low-power electric-field control of altermagnetism in MnTe through strain-mediated coupling in MnTe/PMN-PT heterostructures with negligible Joule heating. Application of +6 kV/cm electric fields induces piezoelectric strain in PMN-PT, modulating the N\'eel temperature from 310 to 328 K. As a result, around the magnetic phase transition, the altermagnetic spin splitting of MnTe is reversibly switched "on" and "off" by the electric fields. Meanwhile, the piezoelectric strain generates lattice distortions and magnetic structure changes in MnTe, enabling up to 9.7% resistance modulation around the magnetic phase transition temperature. Leveraging this effect, we implement programmable resistance states in a Hopfield neuromorphic network, achieving 100% pattern recognition accuracy at <=40% noise levels. This approach establishes the electric-field control as a low-power strategy for altermagnetic manipulation while demonstrating the viability of altermagnetic materials for energy-efficient neuromorphic computing beyond conventional charge-based architectures.

cond-mat.mtrl-sci↗

arXiv2025

Freestanding Thin-Film Materials

Freestanding thin films, a class of low-dimensional materials capable of maintaining structural integrity without substrates, have emerged as a forefront research focus. Their unique advantages-circumventing substrate clamping, liberating intrinsic material properties, and enabling cross-platform heterogeneous integration-underpin this prominence. This review systematically summarizes core fabrication techniques, including physical delamination (e.g., laser lift-off, mechanical exfoliation) and chemical etching, alongside associated transfer strategies. It further explores the induced strain modulation mechanisms, extreme mechanical properties and interface decoupling effects enabled by these films. Representative case studies demonstrate breakthrough applications in flexible/ultrathin electronics, ultrahigh-sensitivity sensors and the exploration of novel quantum states. Critical challenges regarding scalable fabrication, precise interface control, and long-term stability are analyzed, concluding with prospects for emerging applications in bio-inspired intelligent devices, quantum precision sensing, and brain-inspired neural networks.

cond-mat.mtrl-sci↗

arXiv2025

Full Electrical Switching of a Freestanding Ferrimagnetic Metal for Energy-Efficient Bipolar Neuromorphic Computing

Flexible electronics and neuromorphic computing face key challenges in material integration and function retention. In particular, freestanding membranes suffer from slow sacrificial layer removal and interfacial strain, while neuromorphic hardware often relies on area-intensive dual-device schemes for bipolar synaptic weights. Here, we present a universal strategy based on water-soluble Sr4Al2O7 sacrificial layers, enabling the rapid release of freestanding ferrimagnetic metal membranes, which exhibit deterministic spin-orbit torque switching characteristics with well-preserved perpendicular magnetic anisotropy and are potential for next-generation ultrafast information technology. Extending this approach, we realize single-device ferrimagnetic synapses exhibiting intrinsic bipolar resistive switching. When implemented in a ResNet-18 architecture, these devices achieve 92% accuracy on CIFAR-10 - comparable to floating-point software models - while halving device counts relative to differential-pair implementations. These results establish a scalable platform linking flexible spintronics with compact, high-performance neuromorphic systems, offering foundational advances for next-generation electronics and brain-inspired hardware.

cond-mat.mes-hall↗

arXiv2024

Spin-Splitting Magnetoresistance in Altermagnetic RuO2 Thin Films

The recently discovered altermagnets, featured by the exotic correlation of magnetic exchange interaction and alternating crystal environments, have offered exciting cutting-edge opportunities for spintronics. Nevertheless, the altermagnetism of RuO2, one of the earliest-discovered altermagnets, is currently under intense debate. Here we try to resolve this controversy by demonstrating an altermagnetic spin-splitting magnetoresistance (SSMR) effect that is driven by a spin current associated with the giant nonrelativistic spin splitting of an altermagnet. Compared to the spin Hall magnetoresistance induced by a conventional relativistic spin current, the SSMR is characterized by unusual angular dependence with a phase-shift feature underpinned by the Neel-vector orientation and pronounced temperature dependence caused by its susceptibility to electron scattering. Through systematical investigations on the magnetoresistance of (101)-RuO2/Co bilayers, we disentangle a sizable SSMR and hence unveil a Neel vector along [001] direction. Our work not only demonstrates a simple electric avenue to probing the Neel vector of altermagnets, but also indicates long-range magnetic order in thin films of RuO2.

cond-mat.mes-hall↗

arXiv2023

Semiconducting transport in Pb$_{10-x}$Cu$_x$(PO$_4$)$_6$O sintered from Pb$_2$SO$_5$ and Cu$_3$P

The very recent claim on the discovery of ambient-pressure room-temperature superconductivity in modified lead-apatite has immediately excited sensational attention in the entire society, which is fabricated by sintering lanarkite (Pb2SO5) and copper(I) phosphide (Cu$_3$P). To verify this exciting claim, we have successfully synthesized Pb$_2$SO$_5$, Cu$_3$P, and finally the modified lead-apatite Pb$_{10-x}$Cu$_x$(PO$_4$)$_6$O. Detailed electrical transport and magnetic properties of these compounds were systematically analyzed. It turns out that Pb$_2$SO$_5$ is a highly insulating diamagnet with a room-temperature resistivity of ~7.18x10$^9$ Ohm.cm and Cu$_3$P is a paramagnetic metal with a room-temperature resistivity of ~5.22x10$^{-4}$ Ohm.cm. In contrast to the claimed superconductivity, the resulting Pb$_{10-x}$Cu$_x$(PO$_4$)$_6$O compound sintered from Pb$_2$SO$_5$ and Cu$_3$P exhibits semiconductor-like transport behavior with a large room-temperature resistivity of ~1.94x10$^4$ Ohm.cm although our compound shows greatly consistent x-ray diffraction spectrum with the previously reported structure data. In addition, when a pressed Pb$_{10-x}$Cu$_x$(PO$_4$)$_6$O pellet is located on top of a commercial Nd$_2$Fe$_{14}$B magnet at room temperature, no repulsion could be felt and no magnetic levitation was observed either. These results imply that the claim of a room-temperature superconductor in modified lead-apatite may need more careful re-examination, especially for the electrical transport properties.

cond-mat.supr-con↗

arXiv2023

Topotactic Transition: A Promising Opportunity for Creating New Oxides

Topotactic transition is a structural phase change in a matrix crystal lattice mediated by the ordered loss/gain and rearrangement of atoms, leading to unusual coordination environments and metal atoms with rare valent states. As early as in 1990s, low temperature hydride reduction was utilized to realize the topotactic transition. Since then, topological transformations have been developed via multiple approaches. Especially, the recent discovery of the Ni-based superconductivity in infinite-layer nickelates has greatly boosted the topotactic transition mean to synthesizing new oxides for exploring exotic functional properties. In this review, we have provided a detailed and generalized introduction to oxygen-related topotactic transition. The main body of our review include four parts: the structure-facilitated effects, the mechanism of the topotactic transition, some examples of topotactic transition methods adopted in different metal oxides (V, Mn, Fe, Co, Ni) and the related applications. This work is to provide timely and thorough strategies to successfully realize topotactic transitions for researchers who are eager to create new oxide phases or new oxide materials with desired functions.

cond-mat.mtrl-sci↗

arXiv2022

Noncollinear Antiferromagnetic Spintronics

Antiferromagnetic spintronics is one of the leading candidates for next-generation electronics. Among abundant antiferromagnets, noncollinear antiferromagnets are promising for achieving practical applications due to coexisting ferromagnetic and antiferromagnetic merits. In this perspective, we briefly review the recent progress in the emerging noncollinear antiferromagnetic spintronics from fundamental physics to device applications. Current challenges and future research directions for this field are also discussed.

cond-mat.mes-hall↗

arXiv2022

Experimental Progress on the Emergent Infinite-Layer Ni-Based Superconductors

The emergence of the infinite-layer superconducting nickelate thin films marks the Ni age of superconductivity, which has excited a huge surge of studies since the first report in August of 2019. Despite of the tremendous attention drawn from the entire material science community and a large body of theoretical studies, the experimental progress has been relatively slow due to the challenging sample fabrication, which may, in turn, be holding back the fast development of theoretical research. Therefore, a timely and comprehensive review on all the up-to-date experimental progress of the emergent infinite-layer Ni-based superconductors is urgently needed. In this review, we first introduce the history of more than 30-year-long Ni-based superconductivity exploration, then summarize the sample fabrication processes, later present the experimental electrical transport and magnetic properties, and finally come up with several key issues deserving intensive studies. This review is thus expected to be helpful for researchers with diverse research background to readily capture the major progress of this emerging field.

cond-mat.supr-con↗

arXiv2021

Antiferromagnetism in Ni-Based Superconductors

Due to the lack of any magnetic order down to 1.7 K in the parent bulk compound NdNiO2, the recently discovered 9-15 K superconductivity in the infinite-layer Nd0.8Sr0.2NiO2 thin films has provided an exciting playground for unearthing new superconductivity mechanisms. In this letter, we report the successful synthesis of a series of superconducting Nd0.8Sr0.2NiO2 thin films ranging from 8 to 40 nm. We observe the large exchange bias effect between the superconducting Nd0.8Sr0.2NiO2 films and a thin ferromagnetic layer, which suggests the existence of the antiferromagnetic order. Furthermore, the existence of the antiferromagnetic order is evidenced by X-ray magnetic linear dichroism measurements. These experimental results are fundamentally critical for the current field.

cond-mat.supr-con↗

arXiv2021

Epitaxial Integration of a Perpendicularly Magnetized Ferrimagnetic Metal on a Ferroelectric oxide for Electric-Field Control

Ferrimagnets, which contain the advantages of both ferromagnets (detectable moments) and antiferromagnets (ultrafast spin dynamics), have recently attracted great attention. Here we report the optimization of epitaxial growth of a tetragonal perpendicularly magnetized ferrimagnet Mn2Ga on MgO. Electrical transport, magnetic properties and the anomalous Hall effect (AHE) were systematically studied. Furthermore, we successfully integrated high-quality epitaxial ferrimagnetic Mn2Ga thin films onto ferroelectric PMN-PT single crystals with a MgO buffer layer. It was found that the AHE of such a ferrimagnet can be effectively modulated by a small electric field over a large temperature range in a nonvolatile manner. This work thus demonstrates the great potential of ferrimagnets for developing high-density and low-power spintronic devices.

cond-mat.mtrl-sci↗

arXiv2021

Negligible oxygen vacancies, low critical current density, electric-field modulation, in-plane anisotropic and high-field transport of a superconducting Nd0.8Sr0.2NiO2/SrTiO3 heterostructure

The emerging Ni-based superconducting oxide thin films are rather intriguing to the entire condensed matter physics. Here we report some brief experimental results on transport measurements for a 14-nm-thick superconducting Nd0.8Sr0.2NiO2/SrTiO3 thin-film heterostructure with an onset transition temperature of ~9.5 K. Photoluminescence measurements reveal that there is negligible oxygen vacancy creation in the SrTiO3 substrate during thin-film deposition and post chemical reduction for the Nd0.8Sr0.2NiO2/SrTiO3 heterostructure. It was found that the critical current density of the Nd0.8Sr0.2NiO2/SrTiO3 thin-film heterostructure is relatively small, ~4x10^3 A/cm2. Although the surface steps of SrTiO3 substrates lead to an anisotropy for in-plane resistivity, the superconducting transition temperatures are almost the same. The out-of-plane magnetotransport measurements yield an upper critical field of ~11.4 T and an estimated in-plane Ginzburg-Landau coherence length of ~5.4 nm. High-field magnetotransport measurements up to 50 T reveal anisotropic critical fields at 1.8 K for three different measurement geometries and a complicated Hall effect. An electric field applied via the SrTiO3 substrate slightly varies the superconducting transition temperature. These experimental results could be useful for this rapidly developing field.

cond-mat.supr-con↗