arXiv subjects

Xudong Huai

Publications and source records attributed to Xudong Huai.

13 recordsLinked to original sources

arXiv2026

Heat Capacity-A Powerful Tool for Studying Exotic States of Matter

Heat capacity measurements are a powerful tool that researchers rely on when studying the relationship between microscopic degrees of freedom and macroscopic behavior in condensed matter. This uniqueness stems from heat capacity capturing contributions from lattice, electronic, and magnetic components, as well as energy-level populations, enabling an effective approach to studying phase transitions and excitations across different classes of materials. However, analyzing heat capacity data presents a common, appreciable challenge for new researchers. Although comprehensive theoretical aspects of heat capacity are presented in several elegant textbooks, practical application remains a daunting task. To overcome this challenge, this tutorial guides researchers in collecting, analyzing, and interpreting heat capacity data in contemporary quantum materials. We outline the connections between thermodynamics, heat capacity, and entropy, as well as measurement methodology and data analysis for representative examples, including phonon dynamics, spin waves, superconductors, magnetic skyrmions, proximate quantum spin liquids, and heavy-fermion materials. Our goal is to provide a concise, accessible guide that enables new researchers to utilize heat capacity as a quantitative lens for understanding exotic states of matter.

cond-mat.str-el↗

arXiv2026

Co2SeO3Cl2: Studies of Emerging Magnetoelectric Coupling in a Polar, Buckled Honeycomb Material

The development of magnetoelectric materials requires chemical design strategies that integrate structural polarity with magnetic lattices capable of supporting competing spin interactions. Here, we demonstrate such an approach in the polar, buckled honeycomb magnet Co2SeO3Cl2. Magnetization and heat-capacity measurements reveal strong magnetic anisotropy and four successive magnetic transitions at 25.4, 16.8, 11, and 3 K. The recovered magnetic entropy through the ordering regime is only around half of the expected 2Rln(2), indicating persistent spin fluctuations. Second-harmonic generation measurements show three pronounced intensity anomalies at 11, 17, and 26 K that coincide with magnetic transitions while revealing that the crystallographic symmetry is preserved. Together, these results demonstrate that polar, buckled honeycomb magnets offer an unconventional phase space for coupling magnetic and electric dipoles in magnetoelectric materials.

cond-mat.mtrl-sci↗

arXiv2026

Coexisting Paramagnetic Spins and Long-Range Magnetic Order in Ba$_4$(Ru$_{0.92}$Ir$_{0.08}$)$_3$O$_{10}$

We investigate the effect of dilute Ir substitution on the magnetism of the trimer-based ruthenate Ba$_4$Ru$_3$O$_{10}$ using neutron diffraction, magnetic susceptibility measurements, atomistic simulations, and first-principles calculations. Neutron diffraction shows that Ir doping preserves the zigzag antiferromagnetic structure and the ordered-moment magnitude of the parent compound, in which the moments reside exclusively on the two outer Ru(2) sites of each $\rm Ru_3O_{12}$ trimer, while the central Ru(1) site remains nonmagnetic. The Néel temperature is reduced from $\approx\!105$ K to 84.0(1) K upon 8% Ir substitution, while magnetic susceptibility reveals a pronounced low-temperature Curie-like upturn, indicating the coexistence of paramagnetic spins with long-range antiferromagnetic order. Density-functional calculations shows that Ir preferentially occupies the central Ru(1) site, where its extended $5d$ orbitals disrupt the Ru-Ru molecular-orbital network and intra/inter-trimer exchange pathways. Atomistic simulations incorporating this paramagnetic dilution reproduce the suppressed ordering temperature and the coexistence of ordered and paramagnetic components.

cond-mat.str-el↗

arXiv2026

Possible Proximity to Ferromagnetism in the V$_2$Ga$_5$ Superconductor

Superconductivity and ferromagnetism are generally competing ground states in $d$-electron systems, making their interplay of fundamental interest. We report a comprehensive study of high-quality single- and polycrystalline V$_2$Ga$_5$, a bulk type-II superconductor ($T_c = 3.54 \ K$) with a quasi-one-dimensional crystal structure, supplemented with density functional theory (DFT) calculations, suggesting possible proximity to ferromagnetic order. Below $T \approx 10 \ K$, magnetic susceptibility shows ZFC/FC splitting, along with saturation and hysteresis in $M(H)$. Moreover, electrical transport measurements reveal a magnetic-field-dependent resistivity upturn, while specific heat is enhanced in magnetic fields. DFT calculations show that the Fermi level in V$_2$Ga$_5$ is located at a peak in the density of states, with a small magnetic moment per unit cell comparable to the experimental value. Together, these results indicate the possibility that ferromagnetic correlations develop below $T \approx 10 \ K$, well above $T_c$, with long-range ferromagnetic order suppressed by the superconducting transition.

cond-mat.supr-con↗

arXiv2026

Chiral Polar Eu2(SeO3)2(SO4)(H2O)2: A Pathway Toward Narrow Optical Linewidths and Microsecond Lifetimes for Quantum Memory Candidates

Stoichiometric materials of Eu(III) offer a promising platform for quantum memories attributable to their unique capability to display a distinctive, nondegenerate J = 0 transition, which enables precise mapping of optical quantum states into their hyperfine structure for reliable storage and retrieval on demand. However, placing Eu(III) into chiral polar structures, which are necessary for achieving narrow spectral linewidths and long optical lifetimes, is a daunting task. Here, we discover Eu2(SeO3)2(SO4)(H2O)2, a rare Eu(III) material that exhibits chiral polar symmetries encompassing both local and global structures. This unique structure is shaped by an appropriate combination of asymmetric ligands. The chirality fosters dipole-dipole interactions and J-mixing, as characterized by second-harmonic generation, photoluminescence, and magnetic susceptibility. The broken inversion symmetry is supported by the phase-matching behavior of second-harmonic generation. The J = 0 transition is observed at 578 nm with a narrow linewidth at 78 K and a microsecond-scale optical lifetime. The analysis of magnetic susceptibility data using Van Vleck theory results in an effective magnetic moment of 3.33 μB/Eu3+ and J-mixing. Heat capacity data reveal underlying phonon dynamics in the material. This study demonstrates a pathway toward realizing new stoichiometric Eu3+ compounds with potential for optically addressable quantum memory applications.

cond-mat.mtrl-sci↗

arXiv2025

Field-Tailoring Quantum Materials via Magneto-Synthesis: Metastable Metallic and Magnetically Suppressed Phases in a Trimer Iridate

We demonstrate that applying modest magnetic fields during high-temperature crystal growth can profoundly alter the structure and ground state of a spin-orbit-coupled, antiferromagnetic trimer lattice. Using BaIrO3 as a model system, whose ground state is intricately dictated by the trimer lattice, we show that magneto-synthesis, a field-assisted synthesis approach, stabilizes a structurally compressed, metastable metallic and magnetically suppressed phases inaccessible via conventional methods. These effects include a 0.85% reduction in unit cell, 4-order-of-magnitude decrease in resistivity, a 10-fold enhancement of the Sommerfeld coefficient, and the collapse of long-range magnetic order -- all intrinsic and bulk in origin. First-principles calculations confirm that the field-stabilized structure lies substantially above the ground state in energy, highlighting its metastable character. These large, coherent and correlated changes across multiple bulk properties, unlike those caused by dilute impurities, defects or off-stoichiometry, point to an intrinsic field-induced mechanism. The findings establish magneto-synthesis as a powerful new pathway for accessing non-equilibrium quantum phases in strongly correlated materials.

cond-mat.str-el↗

arXiv2025

Treasure Map Toward Skyrmion Evolution in Ambient Conditions: A Perspective from Electronic Instabilities and the Density of Energy

Magnetic skyrmions with topologically protected properties are anticipated to shape the future of electronics. Understanding how skyrmions may evolve in ambient conditions presents a key challenge in the pursuit of technologically significant materials. In this perspective, we focus on electronic instabilities and the density of energy of established skyrmion hosts, where a pathway to a skyrmion phase transition is readily available, to identify signposts for the emergence of skyrmions. We value the impressive research efforts in the field that have built the foundation for many more enticing breakthroughs to come. We share a framework that connects the electronic origins of skyrmion formation to the temperature and field requirements, allowing predictions of candidate materials that may host skyrmions at ambient conditions (the treasure).

cond-mat.mtrl-sci↗

arXiv2025

Atomically Modulating Competing Exchange Interactions in Centrosymmetric Skyrmion Hosts GdRu2X2 (X = Si, Ge)

Magnetic skyrmions are topologically protected spin states enabling high-density, low-power spin electronics. Despite growing efforts to find new skyrmion host systems, the microscopic mechanisms leading to skyrmion phase transitions at specific temperatures and magnetic fields remain elusive. Here, we systematically study the isostructural centrosymmetric magnets- GdRu2X2 (X = Si and Ge), and the role of X-p orbitals in modifying magnetic exchange interactions. GdRu2Ge2 single crystals, synthesized by arc melting, exhibit two high-entropy pockets associated with skyrmion phases at 0.9 T < H < 1.2 T and 1.3 T < H < 1.7 T, 2 K < T < 30 K-more accessible condition at lower fields and higher temperatures than that in the Si counterpart. Entropy estimations from heat capacity measurements align with magnetization data, and transport studies confirm a topological Hall effect, highlighting the system's nontrivial spin textures and Berry curvature. Compared to GdRu2Si2, electronic structure and exchange interaction evaluations reveal the more extended Ge-4p orbitals enhance competing exchange interactions in GdRu2Ge2, thereby manifesting the rich skyrmion behavior. This work demonstrates how modifying exchange interactions at the atomic level enables the tunability of topologically nontrivial electronic states while advancing our understanding of skyrmion formation mechanisms for future spintronics.

cond-mat.mtrl-sci↗

arXiv2025

Jeff = 1/2 Diamond Magnet CaCo2TeO6: A Pathway toward New Spin Physics and Quantum Functions

Diamond lattice magnets, formed by a framework of corner-sharing tetrahedra of magnetic cations, offer unique opportunities to realize novel states of matter for potential utility in information technology. However, research has mostly focused on AB2X4 spinels with Td magnetic ions. This hinders the atomically enabled tunability of competing interactions at different energy scales and the ability to harness many-body electronic states in quantum materials, making the discovery of quantum fluctuations and spin dynamics less accessible. We discover a new material CaCo2TeO6 featuring a diamond lattice of two distinct Oh-Co2+ sites. This material displays strong quantum fluctuations, increased competing magnetic exchange interactions, and field-induced tunability of magnetic structures. The results demonstrate how simple, fundamental refinements in ligand fields can profoundly influence the phase space of quantum matter.

cond-mat.mtrl-sci↗

arXiv2025

Antibonding and Electronic Instabilities in GdRu2X2 (X = Si, Ge, Sn): A New Pathway Toward Developing Centrosymmetric Skyrmion Materials

Chemical bonding is key to unlocking the potential of magnetic materials for future information technology. Magnetic skyrmions are topologically protected nano-sized spin textures that can enable high-density low-power spin-based electronics. Despite increasing interest in the discovery of new skyrmion hosts and their characterization, the electronic origins of the skyrmion formation remain unknown. Here, we study GdRu2X2 (X = Si, Ge, Sn) as a model system to study the connection among chemical bonding, electronic instability, and the critical temperature and magnetic field at which skyrmions evolve. The nature of the electronic structure of GdRu2X2 is characterized by chemical bonding, Fermi surface analysis, and density of energy function. As X-p orbitals become more extended from Si-3p to Ge-4p and Sn-5p, improved interactions between the Gd spins and the [Ru2X2] conduction layer and increased destabilizing energy contributions are obtained. GdRu2Si2 possesses a Fermi surface nesting (FSN) vector [Q = (q, 0, 0)], whereas GdRu2Ge2 displays two inequivalent FSN vectors [Q = (q, 0, 0); QA = (q, q, 0)] and GdRu2Sn2 features multiple Q vectors. In addition, competing ferromagnetic and antiferromagnetic exchange interactions in the Gd plane become more pronounced as a function of X. These results reveal some correlation among the electronic instability, the competing interaction strength, and the temperature and magnetic field conditions at which the skyrmions emerge. This work demonstrates how chemical bonding and electronic structure enable a new framework for understanding and developing skyrmions under desired conditions that would otherwise be impossible.

cond-mat.str-el↗

arXiv2025

Inductive-Effect-Driven Tunability of Magnetism and Lumines-cence in Triangular Layers ANd(SO4)2 (A = Rb, Cs)

Tuning the energy landscape of manybody electronic states in extended solids through the inductive effect-a concept widely used in organic chemistry-offers a new, effective strategy for materials development. Here, we demonstrate this approach using the ANd(SO4)2 (A = Rb, Cs) model system, which possesses different A-site electronegativity and displays a distorted triangular lattice of Nd3+ (4I9/2 ground term). Magnetization data indicate appreciable antiferromagnetic interactions without long-range ordering down to 1.8 K while highlighting the tunable population of the electronic states. Temperature-dependent and time-resolved photoluminescence measurements reveal that emissions and nonradiative processes can be modified by the inductive effect at the atomic level. Heat capacity data confirm no magnetic ordering and add insight into the role of phonons in emission lifetime. Density functional theory calculations prove enhanced covalency in the Cs compound compared to the Rb counterpart while acknowledging the adjustable magnetic intralayer and inter-layer exchange pathways. These results demonstrate a viable framework for utilizing the inductive effect as an important knob for simultaneously dialing in magnetic, optical, and electronic properties in quantum materials.

cond-mat.mtrl-sci↗

arXiv2024

La$_2$O$_3$Mn$_2$Se$_2$: a correlated insulating layered d-wave altermagnet

Altermagnets represent a new class of magnetic phases without net magnetization that are invariant under a combination of rotation and time reversal. Unlike conventional collinear antiferromagnets (AFM), altermagnets could lead to new correlated states and important material properties deriving from their non-relativistic spin-split band structure. Indeed, they are the magnetic analogue of unconventional superconductors and can yield spin polarized electrical currents in the absence of external magnetic fields, making them promising candidates for next-generation spintronics. Here, we report altermagnetism in the correlated insulator, magnetically-ordered tetragonal oxychalcogenide, La$_2$O$_3$Mn$_2$Se$_2$. Symmetry analysis reveals a $\mathit{d}_{x^2 - y^2}$-wave type spin momentum locking, which is supported by density functional theory (DFT) calculations. Magnetic measurements confirm the AFM transition below $\sim$166 K while neutron pair distribution function analysis reveals a 2D short-range magnetic order that persists above the Néel temperature. Single crystals are grown and characterized using X-ray diffraction, optical and electron microscopy, and microRaman spectroscopy to confirm the crystal structure, stoichiometry, and uniformity.

cond-mat.mtrl-sci↗

arXiv2024

Noncentrosymmetric Triangular Magnet CaMnTeO$_6$: Strong Quantum Fluctuations and Role of s0 vs. s2 Electronic States in Competing Exchange Interactions

Noncentrosymmetric triangular magnets offer a unique platform for realizing strong quantum fluctuations. However, designing these quantum materials remains an open challenge attributable to a knowledge gap in the tunability of competing exchange interactions at the atomic level. Here, we create a new noncentrosymmetric triangular S = 3/2 magnet CaMnTeO$_6$ based on careful chemical and physical considerations. The model material displays competing magnetic interactions and features nonlinear optical responses with the capability of generating coherent photons. The incommensurate magnetic ground state of CaMnTeO$_6$ with an unusually large spin rotation angle of 127 deg.(1) indicates that the anisotropic interlayer exchange is strong and competing with the isotropic interlayer Heisenberg interaction. The moment of 1.39(1) $μ$B, extracted from low-temperature heat capacity and neutron diffraction measurements, is only 46% of the expected value of the static moment 3 $μ$B. This reduction indicates the presence of strong quantum fluctuations in the half-integer spin S = 3/2 CaMnTeO$_6$ magnet, which is rare. By comparing the spin-polarized band structure, chemical bonding, and physical properties of AMnTeO$_6$ (A = Ca, Sr, Pb), we demonstrate how quantum-chemical interpretation can illuminate insights into the fundamentals of magnetic exchange interactions, providing a powerful tool for modulating spin dynamics with atomically precise control.

cond-mat.str-el↗