arXiv subjects

Jing-Yang You

Publications and source records attributed to Jing-Yang You.

At least 19 recordsLinked to original sources

arXiv2026

Machine-learning-accelerated discovery of synthesizable high-temperature altermagnets with giant spin splitting

Altermagnets offer a route to spin-polarized electronic states without macroscopic magnetization, because compensated magnetic order can generate momentum-dependent spin splitting through crystal-symmetry-controlled exchange fields. However, experimentally viable altermagnets combining large spin splitting, thermodynamic stability and high magnetic ordering temperatures remain scarce. Here, we develop a machine-learning-accelerated high-throughput framework to explore the tetragonal AB$_2$C$_2$D compounds. Screening 8640 variants identifies 1347 compensated antiferromagnetic candidates satisfying altermagnetic symmetry. An interpretable XGBoost model trained on first-principles spin-splitting data then isolates 34 low-hull-energy candidates,including four previously reported, with giant non-relativistic spin splittings exceeding 1.5 eV near the Fermi level. Detailed first-principles calculations of the representative RbMn$_2$Te$_2$O confirm a maximum spin splitting of $\sim$1.88 eV with dynamical stability and an estimated N\'eel temperature of $\sim$390 K. The giant splitting originates from symmetry-locked Mn-sublattice exchange fields amplified by directional Mn-d/Te-p hybridization. Furthermore, we uncover a profound soft-mode-driven structural transition associated with an interlayer dimensionality crossover in SrMn$_2$Te$_2$O, yet the unfolded electronic structure demonstrates that the altermagnetic spin splitting remains robust after lattice reconstruction. Hydrostatic pressure provides an additional tuning route, producing non-monotonic modulation of the spin-split Fermi surface governed by local coordination and orbital hybridization. These results establish tetragonal AB$_2$C$_2$D compounds as a tunable materials platform for stray-field-free spintronic devices and provide a general data-driven strategy for discovering robust giant-splitting altermagnets.

cond-mat.mtrl-sci↗

arXiv2026

Structural Alter-Phononics: Sublattice-Momentum Locking in Spinless Lattice Dynamics

The discovery of altermagnetism has shown that crystal symmetry can generate momentum-dependent internal polarization without net magnetization. Whether an analogous form of symmetry-organized momentum-space order can exist for spinless lattice vibrations remains unresolved. Here we identify a structural mechanism for $alter$-$phononics$, in which phonon eigenmodes formed from structurally equivalent sublattices acquire momentum-dependent sublattice polarization and frequency splitting in nonmagnetic crystals. The central quantity is the sublattice-resolved dynamical asymmetry $\Delta(\mathbf q)=D_{AA}(\mathbf q)-D_{BB}(\mathbf q)$, which controls the associated eigenvector polarization. We show that this effect requires an alter-generator that maps equivalent sublattices onto one another while rotating the wave vector, together with the absence of inversion exchange and little-group sublattice-exchange constraints that would otherwise enforce sublattice equipartition. These symmetry rules generate nematic $d$-wave, tetragonal $d/g$-wave, and tripartite six-lobe phonon textures. First-principles calculations demonstrate the mechanism in representative nonmagnetic crystals and show how a symmetry-preserving structural distortion can unlock a hidden $d_{x^2-y^2}$-type texture by removing glide-induced equipartition traps while retaining the screw-axis alter-generator. We further show that the eigenvector texture is inherited by sublattice-projected electron-phonon coupling and anharmonic response functions. Our results establish structural alter-phononics as a spinless counterpart to altermagnetic momentum-space order and provide experimentally testable signatures in finite-$\mathbf q$ phonon spectra and displacement patterns.

cond-mat.mtrl-sci↗

arXiv2025

Bilateral hydrogenation induced high-Chern-number quantum anomalous Hall state in monolayer Cr$_2$Ge$_2$Te$_6$

The pursuit of high-temperature quantum anomalous Hall (QAH) insulators faces fundamental challenges, including narrow topological gaps and low Curie temperatures ($T_C$) in existing materials. Here, we propose a strategy using bilateral hydrogenation to engineer a robust QAH state in the topologically trivial ferromagnetic semiconductor Cr$_2$Ge$_2$Te$_6$ via covalent orbital reconstruction. First-principles calculations reveal that by rewiring the orbital hybridization network, hydrogenation alters orbital occupations to shift preexisting Dirac points, originally embedded in the conduction bands, to the vicinity of the Fermi level in Cr$_2$Ge$_2$Te$_6$H$_6$. This electronic restructuring, coupled with spin-orbit coupling, opens a global topological gap of 118.1 meV, establishing a robust QAH state with Chern number $C=3$. Concurrently, this orbital reconstruction tunes the energy difference between the ligand $p$ and transition metal $d$ orbitals. This shift enhances ferromagnetic superexchange via the $d{z^2}-p_z-d_{xz}$ channel, strengthening the nearest-neighbor coupling $J_1$ by 3.06 times and switching $J_2$ from antiferromagnetic to ferromagnetic. Monte Carlo simulations based on extracted exchange parameters indicate a pronounced enhancement of ferromagnetic stability compared with pristine Cr$_2$Ge$_2$Te$_6$. While absolute Curie temperatures depend on the mapping to an effective spin model and represent relative trends, the enhanced stability after hydrogenation is a salient effect. This work establishes targeted orbital reconstruction driven by surface hydrogenation as a powerful route to simultaneously control topology and magnetism in 2D materials, providing a general route to engineer QAH phases with large gaps and high Chern numbers in van der Waals ferromagnetic semiconductors.

cond-mat.mes-hall↗

arXiv2025

Moir\'e excitons in generalized Wigner crystals

Moir\'e superlattices of transition-metal dichalcogenide bilayers host strong Coulomb interactions residing in narrow electron bands, leading to correlated insulating states at fractional carrier doping densities, known as generalized Wigner crystals. In excited states, the formation of moir\'e excitons is expected to be fundamentally shaped by the Wigner-crystal ground states, manifesting an intricate interplay between electronic and excitonic correlations. However, the microscopic description of these Wigner crystalline excitons (WCEs) remains elusive, largely subject to speculations, and is further needed for the understanding of exotic excitonic phases (e.g., exciton insulators and exciton density waves) and their unique properties (e.g., anomalous exciton diffusion). Here, using first-principles many-body GW-Bethe-Salpeter-equation calculations, we directly reveal the internal structures of WCEs in angle-aligned MoSe2/MoS2 moir\'e heterostructure at hole fillings of 1/3 and 2/3. Our results unveil the propagation of correlation effects from the ground state to excited states, shaping the real-space characteristics of WCEs. The strong two-particle excitonic correlations dominate over the kinetic energy of free electron-hole pairs, in analog to the strong single-particle correlations of flat bands. We propose that such unusual excited-state correlation effects of WCEs can be experimentally probed by photocurrent tunneling microscopy. Our work provides a microscopic understanding of strongly correlated WCEs, suggesting them as a highly tunable mixed boson-fermion platform to study many-body interactions and phenomena.

cond-mat.mtrl-sci↗

arXiv2025

Intercalation-Induced Near Room-Temperature Ferromagnetism in CrI3 via Synergistic Exchange Pathways

The development of room-temperature magnetic semiconductors is critical for advancing spintronic technologies, yet van der Waals magnets like CrI3 exhibit intrinsically low Curie temperatures (Tc = 45 K). This study employs first-principles calculations to demonstrate that atom intercalation, particularly lithium (Li), dramatically enhances magnetic exchange couplings in CrI3, achieving near room-temperature ferromagnetism with a predicted Tc of 286 K-aligning with experimental reports of 420 K. The underlying mechanism involves synergistic superexchange and double-exchange interactions: intercalation reduces the |Ep-Ed| energy difference between iodine p-orbitals and chromium d-orbitals, strengthening superexchange pathways, while charge transfer induces valence mixing (e.g., Cr3+ to Cr2+, as confirmed by experimental X-ray photoelectron spectrometry data), promoting double-exchange. Theoretical predictions extend to other intercalants including Cu and Na, with Cu0.25CrI3 and Na0.25CrI3 exhibiting Tc of 267 K and 247 K, respectively, establishing a versatile strategy for designing high-Tc magnetic semiconductors. This work bridges theoretical insights with experimental validation, offering a transferable framework for intercalation-driven material design and accelerating practical spintronic device realization.

cond-mat.mtrl-sci↗

arXiv2025

Enhancement of temperature of quantum anomalous Hall effect in two-dimensional germanene/magnetic semiconductor heterostructures

Quantum anomalous Hall effect (QAHE) is significant for future low-power electronics devices, where a main challenge is realizing QAHE at high temperatures. In this work, based on experimentally reported two-dimensional (2D) germanene and magnetic semiconductors Cr$_2$Ge$_2$Te$_6$ and Cr$_2$Si$_2$Te$_6$, and the first principle calculations, germanene/magnetic semiconductor heterostructures are investigated. Topologically nontrivial edge states and quantized anomalous Hall conductance are demonstrated. It is shown that the QAHE temperature can be enhanced to approximately 62 K in germanene/monolayer (ML) Cr$_2$Ge$_2$Te$_6$ with 2.1\% tensile strain, 64 K in germanene/bilayer (BL) Cr$_2$Ge$_2$Te$_6$ with 1.4\% tensile strain, and 50 K in germanene/ML Cr$_2$Si$_2$Te$_6$ with 1.3\% tensile strain. With increasing tensile strain of these heterostructures, the band gap decreases and the Curie temperature rises, and the highest temperature of QAHE is obtained. Since these 2D materials were discovered in recent experiments, our results provide promising materials for achieving high-temperature QAHE.

cond-mat.mes-hall↗

arXiv2025

Unifying Strain-driven and Pressure-driven Superconductivity in La$_{3}$Ni$_{2}$O$_{7}$: Suppressed charge/spin density waves and enhanced interlayer coupling

Recent strain-stabilized superconductivity at ambient pressure in La$_3$Ni$_2$O$_{7}$ films opens new avenues for nickelates research, in parallel with its pressure-induced counterpart. Using density functional theory calculations, we elucidate the critical factors bridging strain- and pressure-driven superconductivity in La$_3$Ni$_2$O$_{7}$ by comprehensively analyzing structural, electronic, magnetic, and density wave characteristics. Consistent with recent scanning transmission electron microscopy observations, we find an $I4/mmm$ structural transition at $-0.9\%$ strain, preceding superconductivity onset. Electronic analysis shows compressive strain lowers Ni-$d_{z^2}$ orbital energy levels, while interfacial Sr diffusion effectively reconstructs the $d_{z^2}$ pockets, quantitatively matching angle-resolved photoemission spectroscopy experiments. The interlayer antiferromagnetic coupling $J_\perp$ under pressure or strain closely tracks experimental superconducting $T_c$ variation. The dome-shaped pressure dependence and monotonic strain dependence of $J_\perp$ mainly arise from modulations in the apical oxygen $p_z$ energy levels. Moreover, compressive strain suppresses both charge density waves (CDW) and spin density waves (SDW) instabilities analogous to pressure effects, with SDW vanishing concurrently with the structural transition and CDW disappearing at $\sim-3.3\%$ strain. Our results indicate that suppressed density waves and enhanced $J_\perp$ are crucial for both strain- and pressure-driven superconductivity. Accordingly, we propose several candidate substrates capable of achieving greater compressive strain, thereby potentially increasing $T_c$.

cond-mat.supr-con↗

arXiv2025

High Curie temperature in diluted magnetic semiconductors (B, Mn)X (X = N, P, As, Sb)

Doping nonmagnetic semiconductors with magnetic impurities is a feasible way to obtain diluted magnetic semiconductors (DMSs). It is generally accepted that for the most extensively studied DMS, (Ga, Mn)As, its highest Curie temperature T$_{\text{C}}$ was achieved at 200 K with a Mn concentration of approximately 16\% in experiments. A recent experiment reported record-breaking high electron and hole mobilities in the semiconductor BAs [\href{https://www.science.org/doi/10.1126/science.abn4290}{Science 377, 437 (2022)}]. Since BAs shares the same zinc-blende structure with GaAs, here we predict four DMSs (B, Mn)X (X $=$ N, P, As, Sb) by density functional theory calculations. Using a rescaling method to diminish the overestimation of Curie temperature, our results indicate that a significantly higher T$_{\text{C}}$ in the range of 467 K to 485 K for (B, Mn)As with a Mn concentration of around 15.6\% and even higher T$_{\text{C}}$ values above the room temperature for (B, Mn)P with a Mn concentration exceeding 9.4\%. Furthermore, using the method of Ab initio Scattering and Transport (AMSET) with first-principles material parameters, we have predicted a hole mobility of 48.9 cm$^{\text{2}}$V$^{\text{-1}}$s$^{\text{-1}}$ at 300 K for (B, Mn)As with the hole concentration of about n$_{\text{h}}$ $=$ 4.2 $\times$ 10$^{\text{19}}$ cm$^{\text{-3}}$, which is about two times larger than the hole mobility at 300 K in the calculations for (Ga, Mn)As. The hole mobility of (B, Mn)As can be enhanced faster than that of (Ga, Mn)As when the hole concentration is decreased. Our findings predict the emergence of a new family of DMS, (B, Mn)X, and are expected to stimulate both experimental and theoretical studies of the DMS with possible high T$_{\text{C}}$.

cond-mat.mtrl-sci↗

arXiv2024

1D flat bands in phosphorene nanoribbons with pentagonal nature

Materials with flat bands can serve as a promising platform to investigate strongly interacting phenomena. However, experimental realization of ideal flat bands is mostly limited to artificial lattices or moiré systems. Here we report a general way to construct one-dimensional (1D) flat bands in phosphorene nanoribbons (PNRs) with pentagonal nature: penta-hexa-PNRs and penta-dodeca-PNRs, wherein the corresponding 1D flat bands are directly verified by using angle-resolved photoemission spectroscopy. We confirm that the observed 1D flat bands originate from the electronic 1D zigzag and Lieb lattices, respectively, as revealed by the combination of bond-resolved scanning tunneling microscopy, scanning tunneling spectroscopy, tight-binding models, and first-principles calculations. Our study demonstrates a general way to construct 1D flat bands in 1D solid materials system, which provides a robust platform to explore strongly interacting phases of matter.

cond-mat.mtrl-sci↗

arXiv2024

Diverse Manifestations of Electron-Phonon Coupling in a Kagome Superconductor

Recent angle-resolved photoemission spectroscopy (ARPES) experiments on a kagome metal CsV$_3$Sb$_5$ revealed distinct multimodal dispersion kinks and nodeless superconducting gaps across multiple electron bands. The prominent photoemission kinks suggest a definitive coupling between electrons and certain collective modes, yet the precise nature of this interaction and its connection to superconductivity remain to be established. Here, employing the state-of-the-art \textit{ab initio} many-body perturbation theory computation, we present direct evidence that electron-phonon ($e$-ph) coupling induces the multimodal photoemission kinks in CsV$_3$Sb$_5$, and profoundly, drives the nodeless $s$-wave superconductivity, showcasing the diverse manifestations of the $e$-ph coupling. Our calculations well capture the experimentally measured kinks and their fine structures, and reveal that vibrations from different atomic species dictate the multimodal behavior. Results from anisotropic $GW$-Eliashberg equations predict a phonon-mediated superconductivity with nodeless $s$-wave gaps, in excellent agreement with various ARPES and scanning tunneling spectroscopy measurements. Despite of the universal origin from the $e$-ph coupling, the contributions of several characteristic phonon vibrations vary in different phenomena, highlighting a versatile role of $e$-ph coupling in shaping the low-energy excitations of kagome metals.

cond-mat.supr-con↗

arXiv2024

Superconducting and topological properties of compound Lu$_4$H$_7$N

A recent experiment has reported a nitrogen-doped lutetium hydride acheving a remarkable Tc of 294 K at just 1 GPa, significantly reducing the required pressure for obtaining room temperature superconductivity. However, subsequent experimental and theoretical investigations have encountered difficulties in replicating these results, leaving the structure of this Lu-H-N compound shrouded in uncertainty. Here, we propose a stable structure for Lu$_4$H$_7$N employing first-principles calculations. Our calculations reveal that Lu$_4$H$_7$N has a Tc of 1.044 K, which can be substantially enhanced to 11.721 K at 150 GPa, due to the increasing electron-phonon coupling (EPC). Notably, we delve into the nontrivial Z2 band topology of Lu$_4$H$_7$N, featuring discernible surface states near the Fermi level, and we explore its spin Hall conductivity characteristics. Furthermore, we find that the electron doping can enhance the EPC strength and Tc of Lu$_4$H$_7$N, such as the Lu$_4$H$_7$O structure we predict simulating electron doping for Lu$_4$H$_7$N with an impressive Tc of 3.837 K. This work demonstrates the coexistence of superconducting and topological properties in a Lu-H-N system compound, which holds the promise of guiding the search for novel topological superconducting materials.

cond-mat.supr-con↗

arXiv2024

Antiferromagnetic Ground State, Charge Density Waves and Oxygen Vacancies Induced Metal-Insulator Transition in Pressurized La$_{3}$Ni$_{2}$O$_{7}$

La$_{3}$Ni$_{2}$O$_{7}$ has garnered widespread interest recently due to its high-temperature superconductivity under pressure, accompanied by charge density wave (CDW) ordering and metal-insulator (MI) transitions in the phase diagram. Here, we reveal with comprehensive calculations that La$_{3}$Ni$_{2}$O$_{7}$ possesses an antiferromagnetic ground state under both low and high pressures, with the strong Fermi surface nesting contributed by the flat band that leads to phonon softening and electronic instabilities. Several stable CDW orders with oxygen octahedral distortions are identified, which can trigger the MI transitions. The estimated CDW transition temperature ($\approx$120 K) at ambient pressure agrees nicely with experimental results. In the presence of apical oxygen vacancies, we identify two different phases, say, half distortion and full distortion phases, respectively, and their competition can lead to a pressure-induced MI transition, in good agreement with experimental observations. In addition, we find that the electron-phonon coupling is too small to contribute to superconductivity. These results appear to indicate an unconventional superconducting pairing mechanism mediated by antiferromagnetic fluctuations. A phase diagram that is consistent with the experimental results is given. The present results not only explain the origins of experimentally observed CDW and MI transitions, but also provide insight for deeply understanding the properties like superconductivity, CDW and the role of oxygen vacancies in pressurized La$_{3}$Ni$_{2}$O$_{7}$.

cond-mat.supr-con↗

arXiv2023

Observation of Flat Bands and Dirac Cones in a Pyrochlore Lattice Superconductor

Emergent phases often appear when the electronic kinetic energy is comparable to the Coulomb interactions. One approach to seek material systems as hosts of such emergent phases is to realize localization of electronic wavefunctions due to the geometric frustration inherent in the crystal structure, resulting in flat electronic bands. Recently, such efforts have found a wide range of exotic phases in the two-dimensional kagome lattice, including magnetic order, time-reversal symmetry breaking charge order, nematicity, and superconductivity. However, the interlayer coupling of the kagome layers disrupts the destructive interference needed to completely quench the kinetic energy. Here we demonstrate that an interwoven kagome network-a pyrochlore lattice-can host a three dimensional (3D) localization of electron wavefunctions. Meanwhile, the nonsymmorphic symmetry of the pyrochlore lattice guarantees all band crossings at the Brillouin zone X point to be 3D gapless Dirac points, which was predicted theoretically but never yet observed experimentally. Through a combination of angle-resolved photoemission spectroscopy, fundamental lattice model and density functional theory calculations, we investigate the novel electronic structure of a Laves phase superconductor with a pyrochlore sublattice, CeRu$_2$. We observe flat bands originating from both the Ce 4$f$ orbitals as well as from the 3D destructive interference of the Ru 4$d$ orbitals. We further observe the nonsymmorphic symmetry-protected 3D gapless Dirac cones at the X point. Our work establishes the pyrochlore structure as a promising lattice platform to realize and tune novel emergent phases intertwining topology and many-body interactions.

cond-mat.str-el↗

arXiv2023

Single-image based deep learning for precise atomic defects identification

Defect engineering has been profoundly employed to confer desirable functionality to materials that pristine lattices inherently lack. Although single atomic-resolution scanning transmission electron microscopy (STEM) images are widely accessible for defect engineering, harnessing atomic-scale images containing various defects through traditional image analysis methods is hindered by random noise and human bias. Yet the rise of deep learning (DL) offering an alternative approach, its widespread application is primarily restricted by the need for large amounts of training data with labeled ground truth. In this study, we propose a two-stage method to address the problems of high annotation cost and image noise in the detection of atomic defects in monolayer 2D materials. In the first stage, to tackle the issue of data scarcity, we employ a two-state transformation network based on U-GAT-IT for adding realistic noise to simulated images with pre-located ground truth labels, thereby infinitely expanding the training dataset. In the second stage, atomic defects in monolayer 2D materials are effectively detected with high accuracy using U-Net models trained with the data generated in the first stage, avoiding random noise and human bias issues. In both stages, we utilize segmented unit-cell-level images to simplify the model's task and enhance its accuracy. Our results demonstrate that not only sulfur vacancies, we are also able to visualize oxygen dopants in monolayer MoS2, which are usually overwhelmed by random background noise. As the training was based on a few segmented unit-cell-level realistic images, this method can be readily extended to other 2D materials. Therefore, our results outline novel ways to train the model with minimized datasets, offering great opportunities to fully exploit the power of machine learning (ML) applicable to a broad materials science community.

cond-mat.mtrl-sci↗

arXiv2023

Topological chiral kagome lattice

Chirality, a fundamental structural property of crystals, can induce many unique topological quantum phenomena. In kagome lattice, unconventional transports have been reported under tantalizing chiral charge order. Here, we show how by deforming the kagome lattice to obtain a three-dimensional (3D) chiral kagome lattice in which the key band features of the non-chiral 2D kagome lattice - flat energy bands, van Hove singularities (VHSs), and degeneracies - remain robust in both the $k_z$ = 0 and $π$ planes in momentum space. Given the handedness of our kagome lattice, degenerate momentum points possess quantized Chern numbers, ushering in the realization of Weyl fermions. Our 3D chiral kagome lattice surprisingly exhibits 1D behavior on its surface, where topological surface Fermi arc states connecting Weyl fermions are dispersive in one momentum direction and flat in the other direction. These 1D Fermi arcs open up unique possibilities for generating unconventional non-local transport phenomena at the interfaces of domains with different handedness, and the associated enhanced conductance as the separation of the leads on the surface is increased. Employing first-principles calculations, we investigate in-depth the electronic and phononic structures of representative materials within the ten space groups that can support topological chiral kagome lattices. Our study opens a new research direction that integrates the advantages of structural chirality with those of a kagome lattice and thus provides a new materials platform for exploring unique aspects of correlated topological physics in chiral lattices.

cond-mat.mtrl-sci↗

arXiv2023

Family of binary transition metal pnictide superconductors

Superconductivity in transition metal nitrides (TMNs) has been investigated for a long time, such as zirconium nitride (ZrN) with a superconducting transition temperature Tc of 10 K. Recently, a phase diagram has been revealed in ZrNx with different nitrogen concentrations, which is very similar to that of high-temperature copper oxide superconductors. Here, we study the TMNs with face-centered cubic lattice, where ZrN and HfN have been experimentally obtained, and predict eight new stable superconductors by the first-principle calculations. We find that CuN has a high Tc of 30 K with a very strong electron-phonon coupling (EPC) strength. In contrast to ZrN, CuN has softening acoustic phonons at the high symmetry point L, which accounts for its much stronger EPC. In addition, the highly symmetrical structure leads to topological protected nodal points and lines, such as the hourglass Weyl loop in kx/y/z = 0 plane and Weyl points in kx/y/z = 2π/a plane, as well as quadratic band touch at Γ point. CuN could be a topological superconductor. Our results expand the transition metal nitrides superconductor family and would be helpful to guide the search for high temperature topological superconductors.

cond-mat.supr-con↗

arXiv2023

Superconducting, topological and transport properties of kagome metals CsTi$ _{3} $Bi$ _{5} $ and RbTi$ _{3} $Bi$ _{5} $

The recently discovered ATi$_3$Bi$_5$ (A=Cs, Rb) exhibit intriguing quantum phenomena including superconductivity, electronic nematicity, and abundant topological states, which provide promising platforms for studying kagome superconductivity, band topology, and charge orders. In this work, we comprehensively study various properties of ATi$_3$Bi$_5$ including superconductivity under pressure and doping, band topology under pressure, thermal conductivity, heat capacity, electrical resistance, and spin Hall conductivity (SHC) using first-principles calculations. Calculated superconducting transition temperature ($\mathrm{ T_{c}}$) of CsTi$_3$Bi$_5$ and RbTi$_3$Bi$_5$ at ambient pressure are about 1.85 and 1.92K. When subject to pressure, $\mathrm{ T_{c}}$ of CsTi$_3$Bi$_5$ exhibits a special valley and dome shape, which arises from quasi-two-dimensional to three-dimensional isotropic compression within the context of an overall decreasing trend. Furthermore, $\mathrm{ T_{c}}$ of RbTi$_3$Bi$_5$ can be effectively enhanced up to 3.09K by tuning the kagome van Hove singularities (VHSs) and flat band through doping. Pressure can also induce abundant topological surface states at the Fermi energy ($\mathrm{E}_{\mathrm{F}}$) and tune VHSs across $\mathrm{E}_{\mathrm{F}}$. Additionally, our transport calculations are in excellent agreement with recent experiments, confirming the absence of charge density wave. Notably, SHC of CsTi$_3$Bi$_5$ can reach as large as 226$ \hbar\cdot (e\cdot Ω\cdot cm) ^{-1} $ at $\mathrm{E}_{\mathrm{F}}$. Our work provides a timely and detailed analysis of the rich physical properties for ATi$_3$Bi$_5$, offering valuable insights for further explorations and understandings on these intriguing superconducting materials.

cond-mat.supr-con↗

arXiv2023

Intertwining of magnetism and charge ordering in kagome FeGe

Recent experiments report a charge density wave (CDW) in the antiferromagnet FeGe, but the nature of the charge ordering and the associated structural distortion remains elusive. We discuss the structural and electronic properties of FeGe. Our proposed ground state phase accurately captures atomic topographies acquired by scanning tunneling microscopy. We show that the 2$\times$2$\times$1 CDW likely results from the Fermi surface nesting of hexagonal-prism-shaped kagome states. FeGe is found to exhibit distortions in the positions of the Ge atoms instead of the Fe atoms in the kagome layers. Using in-depth first-principles calculations and analytical modeling, we demonstrate that this unconventional distortion is driven by the intertwining of magnetic exchange coupling and CDW interactions in this kagome material. Movement of Ge atoms from their pristine positions also enhances the magnetic moment of the Fe kagome layers. Our study indicates that magnetic kagome lattices provide a material candidate for exploring the effects of strong electronic correlations on the ground state and their implications for transport, magnetic, and optical responses in materials.

cond-mat.mtrl-sci↗