Search

We present X-ray scattering studies resolving structural twinning and phase separation in the charge density wave (CDW) state of the kagome superconductor CsV$_3$Sb$_5$. The three-dimensional CDW state in CsV$_3$Sb$_5$ is reported to form a complex superposition of Star of David (SoD) or Tri-Hexagonal (TrH) patterns of distortion within its kagome planes, but the out-of-plane stacking is marked by metastability. In order to resolve the impact of this metastability, we present reciprocal space mapping and real-space images of CsV$_3$Sb$_5$ collected across multiple length scales using temperature-dependent high-dynamic range mapping (HDRM) and dark-field X-ray microscopy (DFXM). The experimental data provide evidence for a rich microstructure that forms in the CDW state. Data evidence metastability in the formation of $2\times 2\times 4$ and $2\times 2\times 2$ CDW supercells dependent on thermal history and mechanical deformation. We further directly resolve the real space phase segregation of both supercells as well as a real-space, structural twinning driven by the broken rotational symmetry of the CDW state. Our combined results provide insights into the role of microstructure and twinning in experiments probing the electronic properties of CsV$_3$Sb$_5$ where rotational symmetry is broken by the three-dimensional charge density wave order but locally preserved for any single kagome layer., Comment: 12 pages, 9 figures

We report the observation of two-dimensional superconductivity (2D SC) in exfoliated kagome metal CsV$_3$Sb$_5$ with a thickness far thicker than the atomic limit. By examining the critical current and upper critical magnetic fields ($H_{c2}$) of 40-60 nm thick films in the superconducting state, we identify a pronounced Berezinskii-Kosterlitz-Thouless (BKT) transition behavior, i.e. a drastic decrease of the superfluid stiffness near the transition, and a cusp-like feature of the angular dependent $H_{c2}$, both of which serve as direct evidence of 2D SC. In addition, an exceeding of the Pauli paramagnetic limit of the in-plane $H_{c2}$ is consistent with the 2D SC nature. The observed 2D SC occurs in thick films with the highest superconducting transition temperature $T_c$ and the lowest charge density wave transition temperature $T_{\rm {CDW}}$, which suggests that the charge density wave states are interrelated with the superconducting states. Our findings impose constraints in understanding the enhancement of SC in kagome superconductors, and illuminate pathways for achieving novel 2D superconducting states in more stable and much thicker systems., Comment: 6 pages and 4 figures for the main text; 10 pages and 9 figures for the Supplementary Materials

Here we resolve the real-space nature of the high-temperature, short-range charge correlations in the kagome metal ScV$_6$Sn$_6$. Diffuse scattering appears along a frustrated wave vector $\textbf{q}_H=(\frac{1}{3},\frac{1}{3},\frac{1}{2})$ at temperatures far exceeding the charge order transition $T_{CO}=92~\mathrm{K}$, preempting long-range charge order with wave vectors along $\textbf{q}_{\bar{K}}=(\frac{1}{3},\frac{1}{3},\frac{1}{3})$. Using a combination of real space and reciprocal space analysis, we resolve the nature of the interactions between the primary out-of-plane Sc-Sn chain instability and the secondary strain-mediated distortion of the in-plane V kagome network. A minimal model of the diffuse scattering data reveals a high-temperature, short-ranged "zig-zag" phase of in-plane correlations that maps to a frustrated triangular lattice Ising model with antiferromagnetic interactions and provides a real-space understanding of the origin of frustrated charge order in this material., Comment: 6 pages, 4 figures

The rapid advancement of Large Language Models (LLMs) and Large Multimodal Models (LMMs) has heightened the demand for AI-based scientific assistants capable of understanding scientific articles and figures. Despite progress, there remains a significant gap in evaluating models' comprehension of professional, graduate-level, and even PhD-level scientific content. Current datasets and benchmarks primarily focus on relatively simple scientific tasks and figures, lacking comprehensive assessments across diverse advanced scientific disciplines. To bridge this gap, we collected a multimodal, multidisciplinary dataset from open-access scientific articles published in Nature Communications journals. This dataset spans 72 scientific disciplines, ensuring both diversity and quality. We created benchmarks with various tasks and settings to comprehensively evaluate LMMs' capabilities in understanding scientific figures and content. Our evaluation revealed that these tasks are highly challenging: many open-source models struggled significantly, and even GPT-4V and GPT-4o faced difficulties. We also explored using our dataset as training resources by constructing visual instruction-following data, enabling the 7B LLaVA model to achieve performance comparable to GPT-4V/o on our benchmark. Additionally, we investigated the use of our interleaved article texts and figure images for pre-training LMMs, resulting in improvements on the material generation task. The source dataset, including articles, figures, constructed benchmarks, and visual instruction-following data, is open-sourced., Comment: Code and data are available at https://github.com/Leezekun/MMSci

Competing and intertwined orders are ubiquitous in strongly correlated electron systems, such as the charge, spin, and superconducting orders in the high-Tc cuprates. Recent scanning tunneling microscopy (STM) measurements provide evidence for a charge density wave (CDW) that coexists with superconductivity in the heavy Fermion metal UTe2. This CDW persists up to at least 7.5 K and, as a CDW breaks the translational symmetry of the lattice, its disappearance is necessarily accompanied by thermodynamic phase transition. Here, we report high-precision thermodynamic measurements of the elastic moduli of UTe2. We observe no signature of a phase transition in the elastic moduli down to a level of 1 part in 10^7, strongly implying the absence of bulk CDW order in UTe2. We suggest that the CDW and associated pair density wave (PDW) observed by STM may be confined to the surface of UTe2.

Preceding a core-collapse supernova, various processes produce an increasing amount of neutrinos of all flavors characterized by mounting energies from the interior of massive stars. Among them, the electron antineutrinos are potentially detectable by terrestrial neutrino experiments such as KamLAND and Super-Kamiokande via inverse beta decay interactions. Once these pre-supernova neutrinos are observed, an early warning of the upcoming core-collapse supernova can be provided. In light of this, KamLAND and Super-Kamiokande, both located in the Kamioka mine in Japan, have been monitoring pre-supernova neutrinos since 2015 and 2021, respectively. Recently, we performed a joint study between KamLAND and Super-Kamiokande on pre-supernova neutrino detection. A pre-supernova alert system combining the KamLAND detector and the Super-Kamiokande detector was developed and put into operation, which can provide a supernova alert to the astrophysics community. Fully leveraging the complementary properties of these two detectors, the combined alert is expected to resolve a pre-supernova neutrino signal from a 15 M$_{\odot}$ star within 510 pc of the Earth, at a significance level corresponding to a false alarm rate of no more than 1 per century. For a Betelgeuse-like model with optimistic parameters, it can provide early warnings up to 12 hours in advance., Comment: Resubmitted to ApJ. 22 pages, 16 figures, for more information about the combined pre-supernova alert system, see https://www.lowbg.org/presnalarm/

The kagome geometry is an example of frustrated configuration in which rich physics takes place, including the emergence of superconductivity and charge density wave (CDW). Among the kagome metals, ScV$_6$Sn$_6$ hosts an unconventional CDW, with its electronic order showing a different periodicity than that of the phonon which generates it. In this material, a CDW-softened flat phonon band has a second-order collapse at the same time that the first order transition occurs. This phonon band originates from the out-of-plane vibrations of the Sc and Sn atoms, and it is at the base of the electron-phonon-coupling driven CDW phase of ScV$_6$Sn$_6$. Here, we use uniaxial strain to tune the frequency of the flat phonon band, tracking the strain evolution via time-resolved optical spectroscopy and first-principles calculations. Our findings emphasize the capability to induce an enhancement of the unconventional CDW properties in ScV$_6$Sn$_6$ kagome metal through control of strain., Comment: Main text + SM

Product matching, the task of identifying different representations of the same product for better discoverability, curation, and pricing, is a key capability for online marketplace and e-commerce companies. We present a robust multi-modal product matching system in an industry setting, where large datasets, data distribution shifts and unseen domains pose challenges. We compare different approaches and conclude that a relatively straightforward projection of pretrained image and text encoders, trained through contrastive learning, yields state-of-the-art results, while balancing cost and performance. Our solution outperforms single modality matching systems and large pretrained models, such as CLIP. Furthermore we show how a human-in-the-loop process can be combined with model-based predictions to achieve near perfect precision in a production system., Comment: 9 pages, submitted to SIGKDD

The kagome superconductor CsV$_3$Sb$_5$ hosts a variety of charge density wave (CDW) phases, which play a fundamental role in the formation of other exotic electronic instabilities. However, identifying the precise structure of these CDW phases and their intricate relationships remain the subject of intense debate, due to the lack of static probes that can distinguish the CDW phases with identical spatial periodicity. Here, we unveil the competition between two coexisting $2\times2\times2$ CDWs in CsV$_3$Sb$_5$ harnessing time-resolved X-ray diffraction. By analyzing the light-induced changes in the intensity of CDW superlattice peaks, we demonstrate the presence of both phases, each displaying a significantly different amount of melting upon excitation. The anomalous light-induced sharpening of peak width further shows that the phase that is more resistant to photo-excitation exhibits an increase in domain size at the expense of the other, thereby showcasing a hallmark of phase competition. Our results not only shed light on the interplay between the multiple CDW phases in CsV$_3$Sb$_5$, but also establish a non-equilibrium framework for comprehending complex phase relationships that are challenging to disentangle using static techniques., Comment: 10 pages, 4 figures with supplemental Material

A few $4d$ and $5d$ transition metal compounds with various electron fillings were recently found to exhibit magnetic susceptibilities $\chi$ and magnetic moments that deviate from the well-established Kotani model. This model has been considered for decades to be the canonical expression to describe the temperature dependence of magnetism in systems with non-negligible spin-orbit coupling effects. In this work, we uncover the origin of such discrepancies and determine the applicability and limitations of the Kotani model by calculating the temperature dependence of the magnetic moments of a series of $4d$ (Ru-based) and $5d$ (W-based) systems at different electron fillings. For this purpose, we perform exact diagonalization of $ab~initio$-derived relativistic multiorbital Hubbard models on finite clusters and compute their magnetic susceptibilities. Comparison with experimentally measured magnetic properties indicates that contributions such as a temperature independent $\chi_0$ background, crystal field effects, Coulomb and Hund's couplings, and intersite interactions - not included in the Kotani model - are specially crucial to correctly describe the temperature dependence of $\chi$ and magnetic moments at various electron fillings in these systems. Based on our results, we propose a generalized approach to describe their magnetism., Comment: explained clearly the significance of deviations from Kotani model; added three-site cluster studies and calculations including the eg orbital

The PocketWATCH facility is a unique multi-purpose test bed designed to replicate the conditions of large water Cherenkov detectors. Housed at the University of Sheffield, the facility consists of a light-tight 2000L ultrapure water tank with purification and temperature control systems. Water temperature, resistivity, and UV attenuation in the tank are monitored and shown to be stable over time. The system is also shown to be compatible with a solution of 0.2% gadolinium sulfate, allowing further utility in testing equipment bound for the next generation neutrino and nucleon decay water Cherenkov particle detectors. The relevant water quality parameters are shown to be stable whilst running in Gd-mode, thereby providing a suitable test bed for hardware development in a realistic, ex situ environment., Comment: 12 pages, 10 figures

Motivated by the variety of applications in which nematic Hele-Shaw flow occurs, a theoretical model for Hele-Shaw flow of a nematic liquid crystal is formulated and analysed. We derive the thin-film Ericksen-Leslie equations that govern nematic Hele-Shaw flow, and consider two important limiting cases in which we can make significant analytical progress. Firstly, we consider the leading-order problem in the limiting case in which elasticity effects dominate viscous effects, and find that the nematic liquid crystal anchoring on the plates leads to a fixed director field and an anisotropic patterned viscosity that can be used to guide the flow of the nematic. Secondly, we consider the leading-order problem in the opposite limiting case in which viscous effects dominate elasticity effects, and find that the flow is identical to that of an isotropic fluid and the behaviour of the director is determined by the flow. As an example of the insight which can be gained by using the present approach, we then consider the flow of nematic according to a simple model for the squeezing stage of the One Drop Filling method, an important method for the manufacture of Liquid Crystal Displays, in these two limiting cases.

This paper presents the development of a specialized chatbot for materials science, leveraging the Llama-2 language model, and continuing pre-training on the expansive research articles in the materials science domain from the S2ORC dataset. The methodology involves an initial pretraining phase on over one million domain-specific papers, followed by an instruction-tuning process to refine the chatbot's capabilities. The chatbot is designed to assist researchers, educators, and students by providing instant, context-aware responses to queries in the field of materials science. We make the four trained checkpoints (7B, 13B, with or without chat ability) freely available to the research community at https://github.com/Xianjun-Yang/Quokka., Comment: Work in progress

Exotic quantum solids can host electronic states that spontaneously break rotational symmetry of the electronic structure, such as electronic nematic phases and unidirectional charge density waves (CDWs). When electrons couple to the lattice, uniaxial strain can be used to anchor and control this electronic directionality. Here we reveal an unusual impact of strain on unidirectional "smectic" CDW orders in kagome superconductors AV3Sb5 using spectroscopic-imaging scanning tunneling microscopy. We discover local decoupling between the smectic electronic director axis and the direction of anisotropic strain. While the two are generally aligned along the same direction in regions of small CDW gap, the two become misaligned in regions where CDW gap is the largest. This in turn suggests nanoscale variations in smectic susceptibility, which we attribute to a combination of local strain and electron correlation strength. Overall, we observe an unusually high decoupling rate between the smectic electronic director of the 3-state Potts order and anisotropic strain, revealing weak smecto-elastic coupling in the CDW phase of kagome superconductors. This is phenomenologically different from the extensively studied nemato-elastic coupling in the Ising nematic phase of Fe-based superconductors, providing a contrasting picture of how strain can control electronic unidirectionality in different families of quantum materials.

Berry phase and the related concept of Berry curvature can give rise to many unconventional phenomena in solids. In this work, we discover colossal orbital Zeeman effect of topological origin in a newly synthesized bilayer kagome metal TbV6Sn6. We use spectroscopic-imaging scanning tunneling microscopy to study the magnetic field induced renormalization of the electronic band structure. The nonmagnetic vanadium d-orbitals form Dirac crossings at the K point with a small mass gap and strong Berry curvature induced by the spin-orbit coupling. We reveal that the magnetic field leads to the splitting of gapped Dirac dispersion into two branches with giant momentum-dependent g factors, resulting in the substantial renormalization of the Dirac band. These measurements provide a direct observation of the magnetic field controlled orbital Zeeman coupling to the enormous orbital magnetic moments of up to 200 Bohr magnetons near the gapped Dirac points. Interestingly, the effect is increasingly non-linear, and becomes gradually suppressed at higher magnetic fields. Theoretical modeling further confirms the existence of orbital magnetic moments in TbV6Sn6 produced by the non-trivial spin-Berry curvature of the Bloch wave functions. Our work provides the first direct insight into the momentum-dependent nature of topological orbital moments and their tunability by magnetic field concomitant with the evolution of the spin-Berry curvature. Significantly large orbital magnetic moments driven by the Berry curvature can also be generated by other quantum numbers beyond spin, such as the valley in certain graphene-based structures, which may be unveiled using the same tools highlighted in our work.

The recent discovery of the AV$_3$Sb$_5$ (A=K, Rb, Cs) kagome superconductors launched a growing field of research investigating electronic instabilities in kagome metals. Specifically, the AV$_3$Sb$_5$ family naturally exhibits a Fermi level tuned to the Van Hove singularities associated with the saddle points formed from the prototypical kagome band structure. The charge density wave and superconducting states that form within the kagome networks of these compounds exhibit a number of anomalous properties reminiscent of theoretical predictions of exotic states in kagome metals tuned close to their Van Hove fillings. Here we provide an overview of the key structural and electronic features of AV$_3$Sb$_5$ compounds and review the status of investigations into their unconventional electronic phase transitions., Comment: 6 figures, 17 pages

The optical floating zone crystal growth technique is a well-established method for obtaining large, high-purity single crystals. While the floating zone method has been constantly evolving for over six decades, the development of high-pressure (up to 1000 bar) growth systems has only recently been realized via the combination of laser-based heating sources with an all-metal chamber. While our inaugural high-pressure laser floating zone furnace design demonstrated the successful growth of new volatile and metastable phases, the furnace design faces several limitations with imaging quality, heating profile control, and chamber cooling power. Here, we present a second-generation design of the high-pressure laser floating zone furnace, "Laser Optical Kristallmacher II" (LOKII), and demonstrate that this redesign facilitates new advances in crystal growth by highlighting several exemplar materials: ${\alpha}$-Fe$_2$O$_3$, $\beta$-Ga$_2$O$_3$, and La$_2$CuO$_{4+{\delta}}$. Notably, for La$_2$CuO$_{4+{\delta}}$, we demonstrate the feasibility and long-term stability of traveling solvent floating zone growth under a record pressure of 700 bar., Comment: 9 pages, 6 figures

The AV3Sb5 (A = K, Rb, Cs) kagome materials host an interplay of emergent phenomena including superconductivity, charge density wave states, and non-trivial electronic structure topology. The band structures of these materials exhibit a rich variety of features like Dirac crossings, saddle points associated with van Hove singularities, and flat bands prompting significant investigations into the in-plane electronic behavior. However, recent findings including the charge density wave ordering and effects due to pressure or chemical doping point to the importance of understanding interactions between kagome layers. Probing this c-axis electronic structure via experimental methods remains challenging due to limitations of the crystals and, therefore, rigorous computational approaches are necessary to study the interlayer interactions. Here we use first-principles approaches to study the electronic structure of CsV3Sb5 with emphasis on the kz dispersion. We find that the inclusion of nonlocal and dynamical many-body correlation has a substantial impact on the interlayer band structure. We present new band behavior that additionally supports the integration of symmetry in accurately plotting electronic structures and influences further analysis like the calculation of topological invariants., Comment: 9 pages, 4 figures

Pyrochlore materials are characterized by their hallmark network of corner-sharing rare-earth tetrahedra, which can produce a wide array of complex magnetic ground states. Ferromagnetic Ising pyrochlores often obey the "two-in-two-out" spin ice rules, which can lead to a highly-degenerate spin structure. Large moment systems, such as Ho$_2$Ti$_2$O$_7$ and Dy$_2$Ti$_2$O$_7$, tend to host a classical spin ice state with low-temperature spin freezing and emergent magnetic monopoles. Systems with smaller effective moments, such as Pr$^{3+}$-based pyrochlores, have been proposed as excellent candidates for hosting a "quantum spin ice" characterized by entanglement and a slew of exotic quasiparticle excitations. However, experimental evidence for a quantum spin ice state has remained elusive. Here, we show that the low-temperature magnetic properties of Pr$_2$Sn$_2$O$_7$ satisfy several important criteria for continued consideration as a quantum spin ice. We find that Pr$_2$Sn$_2$O$_7$ exhibits a partially spin-frozen ground state with a large volume fraction of dynamic magnetism. Our comprehensive bulk characterization and neutron scattering measurements enable us to map out the magnetic field-temperature phase diagram, producing results consistent with expectations for a ferromagnetic Ising pyrochlore. We identify key hallmarks of spin ice physics, and show that the application of small magnetic fields ($\mu_0 H_c \sim$0.75T) suppresses the spin ice state and induces a long-range ordered magnetic structure. Together, our work clarifies the current state of Pr$_2$Sn$_2$O$_7$ and encourages future studies aimed at exploring the potential for a quantum spin ice ground state in this system.

A wide array of unusual phenomena has recently been uncovered in kagome solids. The charge density wave (CDW) state in the kagome superconductor AV3Sb5 in particular intrigued the community -- the CDW phase appears to break the time-reversal symmetry despite the absence of spin magnetism, which has been tied to exotic orbital loop currents possibly intertwined with magnetic field tunable crystal distortions. To test this connection, precise determination of the lattice response to applied magnetic field is crucial, but can be challenging at the atomic-scale. We establish a new scanning tunneling microscopy based method to study the evolution of the AV3Sb5 atomic structure as a function of magnetic field. The method substantially reduces the errors of typical STM measurements, which are at the order of 1% when measuring an in-plane lattice constant change. We find that the out-of-plane lattice constant of AV3Sb5 remains unchanged (within 10^-6) by the application of both in-plane and out-of-plane magnetic fields. We also reveal that the in-plane lattice response to magnetic field is at most at the order of 0.05%. Our experiments provide further constraints on time-reversal symmetry breaking in kagome metals, and establish a new tool for higher-resolution extraction of the field-lattice coupling at the nanoscale applicable to other quantum materials.

${\lambda}$-RhO$_2$, a prototype 4d transition metal oxide, has been prepared by oxidative delithiation of spinel LiRh$_2$O$_4$ using ceric ammonium nitrate. Average-structure studies of this RhO$_2$ polytype, including synchrotron powder X-ray diffraction and electron diffraction, indicate the room temperature structure to be tetragonal, in the space group I41/amd, with a first-order structural transition to cubic Fd-3m at T = 345 K on warming. Synchrotron X-ray pair distribution function analysis and $^7$Li solid state nuclear magnetic resonance measurements suggest that the room temperature structure displays local Rh-Rh bonding. The formation of these local dimers appears to be associated with a metal-to insulator transition with a non-magnetic ground state, as also supported by density functional theory-based electronic structure calculations. This contribution demonstrates the power of soft chemistry to kinetically stabilize a surprisingly simple binary oxide compound.

This work presents electronic properties of the kagome metal ScV6Sn6 using de Haas-van Alphen (dHvA) oscillations and density functional theory (DFT) calculations. The torque signal with the applied fields up to 43 T shows clear dHvA oscillations with six major frequencies, five of them are below 400 T (low frequencies) and one is nearly 2800 T (high frequency). The Berry phase calculated using the Landau level fan diagram near the quantum limit is approximately {\pi}, which suggests the non-trivial band topology in ScV6Sn6. To explain the experimental data, we computed the electronic band structure and Fermi surface using DFT in both the pristine and charge density wave (CDW) phases. Our results confirm that the CDW phase is energetically favorable, and the Fermi surface undergoes a severe reconstruction in the CDW state. Furthermore, the angular dependence of the dHvA frequencies are consistent with the DFT calculations. The detailed electronic properties presented here are invaluable for understanding the electronic structure and CDWorder in ScV6Sn6, as well as in other vanadium-based kagome systems., Comment: 13 pages, 4 figures

We present and characterize a new member of the $R$Cd$_3$P$_3$ ($R$= rare earth) family of materials, NdCd$_3$P$_3$, which possesses Nd$^{3+}$ cations arranged on well-separated triangular lattice layers. Magnetic susceptibility and heat capacity measurements demonstrate a likely $S_{\mathrm{eff}}$ = 1/2 ground state, and also reveal the formation of long-range antiferromagnetic order at $T_{N} = 0.34$ K. Via measurements of magnetization, heat capacity, and electrical resistivity, we characterize the electronic properties of NdCd$_3$P$_3$ and compare results to density functional theory calculations., Comment: Accepted for publication at Physical Review Materials

MnSiN$_2$ is a transition metal nitride with Mn and Si ions displaying an ordered distribution on the cation sites of a distorted wurtzite-derived structure. The Mn$^{2+}$ ions reside on a 3D diamond-like covalent network with strong superexchange pathways. We simulate its electronic structure and find that the N anions in MnSiN$_2$ act as $\sigma$- and $\pi$-donors, which serve to enhance the N-mediated superexchange, leading to the high N\'{e}el ordering temperature of $T_N$ = 443 K. Polycrystalline samples of MnSiN$_2$ were prepared to reexamine the magnetic structure and resolve previously reported discrepancies. An additional magnetic canting transition is observed at $T_\mathrm{cant}$ = 433 K and the precise canted ground state magnetic structure has been resolved using a combination of DFT calculations and powder neutron diffraction. The calculations favor a $G$-type antiferromagnetic spin order with lowering to $Pc^\prime$. Irreducible representation analysis of the magnetic Bragg peaks supports the lowering of the magnetic symmetry. The computed model includes a 10$^\circ$ rotation of the magnetic spins away from the crystallographic $c$-axis consistent with measured powder neutron diffraction data modeling and a small canting of 0.6$^\circ$., Comment: 9 pages, 6 figures

Broken time-reversal symmetry in the absence of spin order indicates the presence of unusual phases such as orbital magnetism and loop currents. The recently discovered family of kagome superconductors AV$_3$Sb$_5$ (A = K, Rb, or Cs), hosting an exotic charge-density wave (CDW) state, has emerged as a strong candidate for this phase. While initial experiments suggested that the CDW phase breaks time-reversal symmetry, this idea is being intensely debated due to conflicting experimental data. In this work we use laser-coupled scanning tunneling microscopy (STM) to study RbV$_3$Sb$_5$. STM data shows that the Fourier intensities of all three CDW peaks are different, implying that the CDW breaks rotational and mirror symmetries. By applying linearly polarized light along high-symmetry directions, we show that the relative intensities of the CDW peaks can be reversibly switched, implying a substantial electro-striction response, indicative of strong non-linear electron-phonon coupling. A similar CDW intensity switching is observed with perpendicular magnetic fields, which implies an unusual piezo-magnetic response that, in turn, requires time-reversal symmetry-breaking. We show that the simplest CDW that satisfies these constraints and reconciles previous seemingly contradictory experimental data is an out-of-phase combination of bond charge order and loop currents that we dub congruent CDW flux phase. Our laser-STM data opens the door to the possibility of dynamic optical control of complex quantum phenomenon in correlated materials., Comment: main text: 21 pages, 5 figures // Methods and Extended Data: 25 pages, 14 figures

Here we study the effect of electron doping the kagome superconductor CsV$_3$Sb$_5$. Single crystals and powders of CsV$_3$Sb$_{5-x}$Te$_x$ are synthesized and characterized via magnetic susceptibility, nuclear quadrupole resonance, and x-ray diffraction measurements, where we observe a slight suppression of the charge density wave transition temperature and superconducting temperature with the introduction of electron dopants. In contrast to hole-doping, both transitions survive relatively unperturbed up to the solubility limit of Te within the lattice. A comparison is presented between the electronic phase diagrams of electron- and hole-tuned CsV$_3$Sb$_5$., Comment: 11 pages, 4 figures

Here we study the stability of charge order in the kagome metal ScV6Sn6. Synchrotron x-ray diffraction measurements reveal high-temperature, short-range charge correlations at the wave vectors along q=(1/3,1/3,1/2) whose inter-layer correlation lengths diverge upon cooling. At the charge order transition, this divergence is interrupted and long-range order freezes in along q=(1/3,1/3,1/3), as previously reported, while disorder enables the charge correlations to persist at the q=(1/3,1/3,1/2) wave vector down to the lowest temperatures measured. Both short-range and long-range charge correlations seemingly arise from the same instability and both are rapidly quenched upon the introduction of larger Y ions onto the Sc sites. Our results validate the theoretical prediction of the primary lattice instability at q=(1/3,1/3,1/2), and we present a heuristic picture for viewing the frustration of charge order in this compound.

We present a neutron diffraction study of NaYbO$_2$, a candidate quantum spin liquid compound hosting a geometrically frustrated triangular lattice of magnetic Yb$^{3+}$ ions. We observe diffuse magnetic scattering that persists to at least 20 K, demonstrating the presence of short-range magnetic correlations in this system up to a relatively high energy scale. Using reverse Monte Carlo and magnetic pair distribution function analysis, we confirm the predominant antiferromagnetic nature of these correlations and show that the diffuse scattering data can be well described by noninteracting layers of XY spins on the triangular lattice. We rule out Ising spins and short-range-ordered stripe or 120$^{\circ}$ phases as candidate ground states of NaYbO$_2$. These results are consistent with a possible QSL ground state in NaYbO$_2$ and showcase the benefit of combined reciprocal- and real-space analysis of materials with short-range magnetic correlations.

We characterize the magnetic ground state of the topological kagome metal GdV$_6$Sn$_6$ via resonant X-ray diffraction. Previous magnetoentropic studies of GdV$_6$Sn$_6$ suggested the presence of a modulated magnetic order distinct from the ferromagnetism that is easily polarized by the application of a magnetic field. Diffraction data near the Gd-$L_2$ edge directly resolve a $c$-axis modulated spin structure order on the Gd sublattice with an incommensurate wave vector that evolves upon cooling toward a partial lock-in transition. While equal moment (spiral) and amplitude (sine) modulated spin states can not be unambiguously discerned from the scattering data, the overall phenomenology suggests an amplitude modulated state with moments predominantly oriented in the $ab$-plane. Comparisons to the ``double-flat" spiral state observed in Mn-based $R$Mn$_6$Sn$_6$ kagome compounds of the same structure type are discussed., Comment: 5 pages, 4 figures