Disentangling the intertwined orders in a magnetic kagome metal.

Intertwined orders appear when multiple orders are strongly interacting, and kagome metals have emerged as new platforms to explore exotic phases. FeGe has been found to develop a charge density wave (CDW) order within magnetic phase, suggesting an intricate interplay of the lattice, charge, and spin degrees of freedom. Recently, postgrowth annealing has been proposed to tune the CDW order from long-range to complete suppression, offering a tuning knob for the CDW order.

Atomic manipulation of the emergent quasi-2D superconductivity and pair density wave in a kagome metal.

The unconventional charge density wave (CDW) order in layered kagome lattice superconductors AVSb (A = K, Cs or Rb) triggers the emergence of novel quantum states such as time-reversal symmetry breaking and electronic liquid crystal states. However, atomic-scale manipulation and control of such phases remains elusive. Here we observe the emergent superconductivity and a primary pair density wave at the 2 × 2 Cs reconstructed surface of CsVSb by means of low-temperature scanning tunnelling microscopy/spectroscopy paired with density functional theory calculations.

High-temperature surface state in Kondo insulator UBiNi.

The resurgence of interest in Kondo insulators has been driven by two major mysteries: the presence of metallic surface states and the observation of quantum oscillations. To further explore these mysteries, it is crucial to investigate another similar system beyond the two existing ones, SmB and YbB. Here, we address this by reporting on a Kondo insulator, UBiNi.

Revealing the Orbital Origins of Exotic Electronic States with Ti Substitution in Kagome Superconductor CsV_{3}Sb_{5}.

The multiband kagome superconductor CsV_{3}Sb_{5} exhibits complex orbital textures on the Fermi surface, making the orbital origins of its cascade of correlated electronic states and superconductivity a major scientific puzzle. Chemical doping of the kagome plane can simultaneously tune the exotic states and the Fermi-surface orbital texture and thus offers a unique opportunity to correlate the given states with specific orbitals. In this Letter, by substituting V atoms with Ti in the kagome superconductor CsV_{3}Sb_{5}, we reveal the orbital origin of a cascade of its correlated electronic states through the orbital-resolved quasiparticle interference.

Persistent flat band splitting and strong selective band renormalization in a kagome magnet thin film.

Magnetic kagome materials provide a fascinating playground for exploring the interplay of magnetism, correlation and topology. Many magnetic kagome systems have been reported including the binary FeX (X = Sn, Ge; m:n = 3:1, 3:2, 1:1) family and the rare earth RMnSn (R = rare earth) family, where their kagome flat bands are calculated to be near the Fermi level in the paramagnetic phase. While partially filling a kagome flat band is predicted to give rise to a Stoner-type ferromagnetism, experimental visualization of the magnetic splitting across the ordering temperature has not been reported for any of these systems due to the high ordering temperatures, hence leaving the nature of magnetism in kagome magnets an open question.

Spin-Charge-Lattice Coupling across the Charge Density Wave Transition in a Kagome Lattice Antiferromagnet.

Understanding spin and lattice excitations in a metallic magnetic ordered system forms the basis to unveil the magnetic and lattice exchange couplings and their interactions with itinerant electrons. Kagome lattice antiferromagnet FeGe is interesting because it displays a rare charge density wave (CDW) deep inside the antiferromagnetic ordered phase that interacts with the magnetic order. We use neutron scattering to study the evolution of spin and lattice excitations across the CDW transition T_{CDW} in FeGe.

Hidden non-collinear spin-order induced topological surface states.

Rare-earth monopnictides are a family of materials simultaneously displaying complex magnetism, strong electronic correlation, and topological band structure. The recently discovered emergent arc-like surface states in these materials have been attributed to the multi-wave-vector antiferromagnetic order, yet the direct experimental evidence has been elusive. Here we report observation of non-collinear antiferromagnetic order with multiple modulations using spin-polarized scanning tunneling microscopy.

Atomistic Origin of Diverse Charge Density Wave States in CsV_{3}Sb_{5}.

Kagome metals AV_{3}Sb_{5} (A=K, Rb, or Cs) exhibit intriguing charge density wave (CDW) instabilities, which interplay with superconductivity and band topology. However, despite firm observations, the atomistic origins of the CDW phases, as well as hidden instabilities, remain elusive. Here, we adopt our newly developed symmetry-adapted cluster expansion method to construct a first-principles-based effective Hamiltonian of CsV_{3}Sb_{5}, which not only reproduces the established inverse star of David (ISD) phase, but also predict a series of D_{3h}-n states under mild tensile strains.

Atomically precise engineering of spin-orbit polarons in a kagome magnetic Weyl semimetal.

Atomically precise defect engineering is essential to manipulate the properties of emerging topological quantum materials for practical quantum applications. However, this remains challenging due to the obstacles in modifying the typically complex crystal lattice with atomic precision. Here, we report the atomically precise engineering of the vacancy-localized spin-orbit polarons in a kagome magnetic Weyl semimetal CoSnS, using scanning tunneling microscope.

Competing itinerant and local spin interactions in kagome metal FeGe.

The combination of a geometrically frustrated lattice, and similar energy scales between degrees of freedom endows two-dimensional Kagome metals with a rich array of quantum phases and renders them ideal for studying strong electron correlations and band topology. The Kagome metal, FeGe is a noted example of this, exhibiting A-type collinear antiferromagnetic (AFM) order at T ≈ 400 K, then establishes a charge density wave (CDW) phase coupled with AFM ordered moment below T ≈ 110 K, and finally forms a c-axis double cone AFM structure around T ≈ 60 K. Here we use neutron scattering to demonstrate the presence of gapless incommensurate spin excitations associated with the double cone AFM structure of FeGe at temperatures well above T and T that merge into gapped commensurate spin waves from the A-type AFM order.

Tunable vortex bound states in multiband CsVSb-derived kagome superconductors.

Vortices and bound states offer an effective means of comprehending the electronic properties of superconductors. Recently, surface-dependent vortex core states have been observed in the newly discovered kagome superconductors CsVSb. Although the spatial distribution of the sharp zero energy conductance peak appears similar to Majorana bound states arising from the superconducting Dirac surface states, its origin remains elusive.

Direct observation of the collective modes of the charge density wave in the kagome metal CsVSb.

A recently discovered group of kagome metals AV[Formula: see text]Sb[Formula: see text] (A = K, Rb, Cs) exhibit a variety of intertwined unconventional electronic phases, which emerge from a puzzling charge density wave phase. Understanding of this charge-ordered parent phase is crucial for deciphering the entire phase diagram. However, the mechanism of the charge density wave is still controversial, and its primary source of fluctuations-the collective modes-has not been experimentally observed.

Abundant Lattice Instability in Kagome Metal ScV_{6}Sn_{6}.

Kagome materials are emerging platforms for studying charge and spin orders. In this Letter, we have revealed a rich lattice instability in a Z_{2} kagome metal ScV_{6}Sn_{6} by first-principles calculations. Beyond verifying the sqrt[3]×sqrt[3]×3 charge density wave (CDW) order observed by the recent experiment, we further identified three more possible CDW structures, i.

Distinct Magnetic Gaps between Antiferromagnetic and Ferromagnetic Orders Driven by Surface Defects in the Topological Magnet MnBi_{2}Te_{4}.

Many experiments observed a metallic behavior at zero magnetic fields (antiferromagnetic phase, AFM) in MnBi_{2}Te_{4} thin film transport, which coincides with gapless surface states observed by angle-resolved photoemission spectroscopy, while it can become a Chern insulator at field larger than 6 T (ferromagnetic phase, FM). Thus, the zero-field surface magnetism was once speculated to be different from the bulk AFM phase. However, recent magnetic force microscopy refutes this assumption by detecting persistent AFM order on the surface.

Strong room-temperature bulk nonlinear Hall effect in a spin-valley locked Dirac material.

Nonlinear Hall effect (NLHE) is a new type of Hall effect with wide application prospects. Practical device applications require strong NLHE at room temperature (RT). However, previously reported NLHEs are all low-temperature phenomena except for the surface NLHE of TaIrTe.

Emergent topological quantum orbits in the charge density wave phase of kagome metal CsVSb.

The recently discovered kagome materials VSb ( = K, Rb, Cs) attract intense research interest in intertwined topology, superconductivity, and charge density waves (CDW). Although the in-plane 2 × 2 CDW is well studied, its out-of-plane structural correlation with the Fermi surface properties is less understood. In this work, we advance the theoretical description of quantum oscillations and investigate the Fermi surface properties in the three-dimensional CDW phase of CsVSb.

Titanium doped kagome superconductor CsVTiSb and two distinct phases.

The vanadium-based kagome superconductor CsVSb has attracted tremendous attention due to its unexcepted anomalous Hall effect (AHE), charge density waves (CDWs), nematicity, and a pseudogap pair density wave (PDW) coexisting with unconventional strong-coupling superconductivity. The origins of CDWs, unconventional superconductivity, and their correlation with different electronic states in this kagome system are of great significance, but so far, are still under debate. Chemical doping in the kagome layer provides one of the most direct ways to reveal the intrinsic physics, but remains unexplored.

[Spatial and Temporal Distribution and Source Variation of Heavy Metals in Cultivated Land Soil of Xiangzhou District Based on EBK Interpolation Prediction and GDM Model].

In order to explore the spatial and temporal changes in spatial patterns and source changes in heavy metals in Xiangzhou District, 395 and 326 soil samples were collected from cultivated soil in Xiangzhou District in November 2009 and November 2019, respectively. The contents of Cr, Pb, As, Hg, and Cd during these two years were measured. The spatial pattern and variation distribution of five types of heavy metals during these two years were obtained by using the empirical Bayesian Kriging (EBK) method.

Observation of anomalous amplitude modes in the kagome metal CsVSb.

The kagome lattice provides a fertile platform to explore novel symmetry-breaking states. Charge-density wave (CDW) instabilities have been recently discovered in a new kagome metal family, commonly considered to arise from Fermi-surface instabilities. Here we report the observation of Raman-active CDW amplitude modes in CsVSb, which are collective excitations typically thought to emerge out of frozen soft phonons, although phonon softening is elusive experimentally.

Roton pair density wave in a strong-coupling kagome superconductor.

The transition metal kagome lattice materials host frustrated, correlated and topological quantum states of matter. Recently, a new family of vanadium-based kagome metals, AVSb (A = K, Rb or Cs), with topological band structures has been discovered. These layered compounds are nonmagnetic and undergo charge density wave transitions before developing superconductivity at low temperatures.

Charge Density Waves and Electronic Properties of Superconducting Kagome Metals.

Kagome metals AV_{3}Sb_{5} (A=K, Rb, and Cs) exhibit intriguing superconductivity below 0.9∼2.5  K, a charge density wave (CDW) transition around 80∼100  K, and Z_{2} topological surface states.

Large Fermi-Energy Shift and Suppression of Trivial Surface States in NbP Weyl Semimetal Thin Films.

Weyl semimetals, a class of 3D topological materials, exhibit a unique electronic structure featuring linear band crossings and disjoint surface states (Fermi-arcs). While first demonstrations of topologically driven phenomena have been realized in bulk crystals, efficient routes to control the electronic structure have remained largely unexplored. Here, a dramatic modification of the electronic structure in epitaxially grown NbP Weyl semimetal thin films is reported, using in situ surface engineering and chemical doping strategies that do not alter the NbP lattice structure and symmetry, retaining its topological nature.

Accuracy trade-off between one-electron and excitonic spectra of cuprous halides in first-principles calculations.

Because of the sophisticated error cancellation in the density functional theory (DFT)-based calculations, a theoretically more accurate input would not guarantee a better output. In this work, our first-principles GW plus Bethe-Salpeter equation calculations using pseudopotentials show that cuprous halides (CuCl and CuBr) are such extreme cases for which a better one-electron band is not accompanied with a better exciton binding energy. Moreover, we find that the exchange interaction of Cu core electrons plays a crucial role in their ground-state electronic properties, especially in the energy gap and macroscopic dielectric constant.

Electric-Field Switching of Magnetic Topological Charge in Type-I Multiferroics.

Applying electric field to control magnetic properties is a very efficient way for spintronics devices. However, the control of magnetic characteristics by electric fields is not straightforward, due to the time-reversal symmetry of magnetism versus spatial inversion symmetry of electricity. Such fundamental difficulty makes it challenging to modify the topology of magnetic skyrmionic states with electric field.