Kagome Lattice Structure Research Articles

On-Chip Synthesis of Quasi-2D Semimetals from Multi-Layer Chalcogenides.

Reducing the dimensions of materials from three to two, or quasi-two, provides a fertile platform for exploring emergent quantum phenomena and developing next-generation electronic devices. However, growing high-quality, ultrathin, quasi2D materials in a templated fashion on an arbitrary substrate is challenging. Here, the study demonstrates a simple and reproducible on-chip approach for synthesizing non-layered, nanometer-thick, quasi-2D semimetals. In one implementation, this method starts with thin semiconducting InSe flakes of below 20nm in thickness with nickel deposited on top, followed by a low-temperature annealing step that results in a controlled transformation of the layered InSe to a non-layered, crystalline semimetal via reaction with the laterally diffusing nickel. Atomic resolution microscopy reveals the transformed semimetal to be Ni3In2Se2 with a Kagome-lattice structure. Moreover, it is demonstrated that this synthesis method is generalizable by transforming 2D layered chalcogenides such as SnS and SnSe employing Ni and Co to non-layered semimetals, paving the way for engineering novel types of devices.

Compression and energy absorption of wood-based reinforced 3D Kagome lattice structures

3D Kagome lattice sandwich structure is recognized as the most excellent lattice configuration. However, the preparation method of 3D Kagome is complicated and the raw materials for its preparation are limited to materials with high plasticity. In this study, we developed a wood-based 3D Kagome lattice structure that combines discrete rods into a continuous core using reinforcement. Orthogonal tests, theoretical analysis, and finite element simulations were performed to investigate the correlation between the dimensional parameters, the mechanical properties, and the energy absorption capacity. The damage modes were found to be mainly bending fracture, core shear, and panel rupture, with the use of reinforcement affecting the damage modes. Compressive properties of the 3D Kagome lattice structure are increased by increasing core diameter and inclination degree, decreasing core in-cut diameter, and using high-strength reinforcements. Finite element simulations further confirm that the use of high-strength reinforcements changes the stress distribution of the lattice structure. The 3D Kagome lattice structure with an inclination degree of 65°, a core diameter of 10 mm, a reinforcement wall thickness of 2 mm, and a core in-cut diameter of 2 mm has the optimal compression performance and energy absorption capacity.

A single crystal study of Kagome metals U2Mn3Ge and U2Fe3Ge

Single crystals of U2Mn3Ge and U2Fe3Ge with a Kagome lattice structure were synthesized using a high-temperature self-flux crystal growth method. The physical properties of these crystals were characterized through measurements of resistivity, magnetism, and specific heat. U2Fe3Ge exhibits ferromagnetic ground state and anomalous Hall effect, and U2Mn3Ge demonstrates a complex magnetic structure. Both compounds exhibit large Sommerfeld coefficient, indicating coexistence of heavy Fermion behaviour with magnetism. Our results suggest that this U2TM3Ge (TM = Mn, Fe, Co) family is a promising platform to investigate the interplay of magnetism, Kondo physics and the Kagome lattice.

Symmetry Breaking and Ascending in the Magnetic Kagome Metal FeGe

Spontaneous symmetry breaking—the phenomenon in which an infinitesimal perturbation can cause the system to break the underlying symmetry—is a cornerstone concept in the understanding of interacting solid-state systems. In a typical series of temperature-driven phase transitions, higher-temperature phases are more symmetric due to the stabilizing effect of entropy that becomes dominant as the temperature is increased. However, the opposite is rare but possible when there are multiple degrees of freedom in the system. Here, we present such an example of a symmetry-ascending phenomenon upon cooling in a magnetic kagome metal FeGe by utilizing neutron Larmor diffraction and Raman spectroscopy. FeGe has a kagome lattice structure with simple A-type antiferromagnetic order below Néel temperature TN≈400 K and a charge density wave (CDW) transition at TCDW≈110 K, followed by a spin-canting transition at around 60 K. In the paramagnetic state at 460 K, we confirm that the crystal structure is indeed a hexagonal kagome lattice. On cooling to around TN, the crystal structure changes from hexagonal to monoclinic with in-plane lattice distortions on the order of 10−4 and the associated splitting of the double-degenerate phonon mode of the pristine kagome lattice. Upon further cooling to TCDW, the kagome lattice shows a small negative thermal expansion, and the crystal structure gradually becomes more symmetric upon further cooling. A tendency of increasing the crystalline symmetry upon cooling is unusual; it originates from an extremely weak structural instability that coexists and competes with the CDW and magnetic orders. These observations are against the expectations for a simple model with a single order parameter and hence can only be explained by a Landau free energy expansion that takes into account multiple lattice, charge, and spin degrees of freedom. Thus, the determination of the crystalline lattice symmetry as well as the unusual spin-lattice coupling is a first step towards understanding the rich electronic and magnetic properties of the system, and it sheds new light on intertwined orders where the lattice degree of freedom is no longer dominant. Published by the American Physical Society 2024

Quantum oscillations revealing topological band in kagome metal ScV6Sn6

Compounds with kagome lattice structure are known to exhibit Dirac cones, flatbands, and van Hove singularities, which host numerous versatile quantum phenomena. Inspired by these intriguing properties, we investigate the temperature and magnetic field-dependent electrical transports along with the theoretical calculations of ScV6Sn6, a nonmagnetic charge-density wave (CDW) compound. At low temperatures, the compound exhibits Shubnikov–de Haas quantum oscillations, which help to design the Fermi-surface (FS) topology. This analysis reveals the existence of several small FSs in the Brillouin zone, combined with a large FS. Among them, the FS-possessing Dirac band is nontrivial and generates a nonzero Berry phase. In addition, the compound also shows the anomalous Hall-like behavior up to the CDW phase transition, and they might be correlated. Combining these interesting physical properties with the CDW phase, ScV6Sn6 presents a unique material example of the versatile HfFe6Ge6 family and provides various promising opportunities to explore the series further. Published by the American Physical Society 2024

A negative photoconductivity photodetector based on two-dimensional Nb3Cl8.

Negative photoconductivity (NPC)-based photodetectors offer a new direction for energy-efficient photodetection technologies, featuring low energy consumption and high responsivity. Two-dimensional (2D) materials are particularly promising for implementing NPC due to their large surface area, abundant surface states, and tunable bandgap properties. In this context, 2D Nb3Cl8, with its unique kagome lattice structure and broad absorption spectrum, has attracted considerable interest. Notably, metal halides such as Nb3Cl8 demonstrate significant potential as NPC materials due to their low anionic and cationic bonding strength, which allows for the formation of vacancy defects with high probability. However, the NPC characteristics of Nb3Cl8 have not been thoroughly investigated. In this study, we fabricated field-effect transistors (FETs) using Nb3Cl8 single crystals synthesized via chemical vapor transport (CVT). These devices exhibited an electron mobility of 4.24 × 10-3 cm2 V-1 s-1 and a high Ion/Ioff ratio of 1.42 × 104. Notably, Nb3Cl8-based photodetectors demonstrated consistent NPC behavior across a wide wavelength range of 400-1050 nm, with a high responsivity of 156.82 mA W-1 at 400 nm. We propose that the trapping effect due to defect levels within the bandgap is the primary cause of this NPC phenomenon. The present findings reveal the unique photodetector properties of Nb3Cl8 and highlight its promise in energy-efficient photodetectors and various optoelectronic applications.

Parametric studies and compressive performance of GH4169/K465 Kagome lattice structure prepared by selective laser melting

This paper is proposed a sufficient strategy to enhance the Kagome lattice structure by introducing sphere connections at the joints of the rods. Three types of lattice structures, namely single-cell Kagome, sandwich monocyte, and multi-layer sandwich GH4169/K465, were fabricated through the selective laser melting method. Experimental results demonstrated that the load peak value of the lattice structure increased gradually with variations in rod diameter and angle. When the rod diameter is 2 mm and the angle is 50°, the comprehensive performance is relatively excellent. Both the single-cell Kagome and sandwich monocyte structures exhibited a secondary load peak curve for the load versus displacement curve.The primary failure mode of the spherical connections Kagome structure is member fracture. For sandwich cell structures, when the rod diameter is 1.1 mm, the elastic modulus, yield strength and energy absorption of SRK are 412 MPa, 17.02 MPa and 8.05 MJ/mm3, respectively. When the rod diameter is increased to 1.7 mm, the properties of SRK are 561 MPa, 84.32 MPa and 35.49 MJ/mm3, respectively. The properties of SRK gradually increase with the increase of rod diameter. the elastic modulus, yield strength, and energy absorption of strut-reinforced Kagome with varying rod diameters surpass those of both the Kagome and spherical connections Kagome structures. The failure mode in strut-reinforced Kagome structures is primarily due to rod buckling. In the compressive stress-strain curve of the multi-layer sandwich structure,when the deformation amount is 0.2, SRK has a higher compressive strength than Kagome and SCK structure, which can reach about 350 MPa, while Kagome and SCK are lower than 200 MPa. demonstrated a gradual increasing trend in stress with increasing strain. In addition, the mechanical properties of the Kagome lattice structure are enhanced due to partial structural failure, with fracture occurring in certain members.

On-Surface Synthesis of Novel Kagome Lattices Coordinated via Four-Fold N-Ag Bonding.

The Kagome lattice structures based on metal-organic coordination have garnered widespread interest because of their topologically Dirac/flat bands and other exotic electronic structures. However, the experimental fabrication of large-area two-dimensional (2D) Kagome lattice structures of metal-organic frameworks (MOFs) via on-surface synthesis remains limited. Herein, we successfully construct two kinds of large-scale 2D Kagome-type lattices stabilized by 4-fold N-Ag coordination on the Ag(111) surface. With the aid of scanning tunneling microscopy (STM) and synchrotron radiation photoemission spectroscopy (SRPES), we clearly elucidate the reaction pathway and mechanism of fabrication of the two Kagome lattices. This work provides a novel platform for investigating related intriguing physical properties.

Design parameters of a Kagome lattice structure constructed by fused deposition modeling: a response surface methodology study

Design parameters of a Kagome lattice structure constructed by fused deposition modeling: a response surface methodology study

Magnetic phases of the frustrated ferromagnetic spin-trimer system Gd3Ru4Al12 with a distorted kagome lattice structure

The magnetization and specific heat measurements have been performed on single-crystalline Gd_3_Ru_4_Al_12_ with a distorted Kagome lattice structure. This spin system is regarded as an antiferromagnetic triangular lattice of XY like Heisenberg model at low temperatures. The magnetic phase diagrams indicate the existence of frustration and Z_2_ degeneracy. The magnetization and specific heat imply the successive phase transitions with partial disorder and a T-shaped spin structure in the ground state.

Anomalous Hall effect dominated by intrinsic mechanism in Fe3Ge with hexagonal DO19 Kagome lattice and cubic DO3 structure

Intrinsic large anomalous Hall effect (AHE) due to Berry curvature (BC) has attracted much attention in recent years not only for the fundamental research but also for the potential application prospect in sensors. Iron-based alloys are one of the representative materials. In this paper, the AHE has been studied in Fe3Ge alloys with DO19 and DO3 structures. Experimental results show that both of the samples have ferromagnetic properties with spontaneous moment of 5.51 and 5.29 μB/f.u. at 5 K for DO19 and DO3 Fe3Ge, respectively. The temperature dependence of longitudinal resistivity at a zero field makes clear that DO19 and DO3 Fe3Ge have a metal behavior. The value of anomalous Hall conductivity (AHC) for DO19 and DO3 polycrystalline Fe3Ge at room temperature is 175 and 106 S/cm, respectively. It is analyzed that AHC is mainly dominated by the intrinsic scattering associated with the BC. The band structures with and without spin–orbit coupling (SOC) indicates that the nodal line will gap out at the EF due to the perturbation of SOC in DO19 Fe3Ge, which induces a large BC in the sample, leading to a great AHC. In the DO3 structure, a degenerate band along the L–G path is split, producing an enhanced BC and AHC. Stable AHC up to room temperature makes Fe3Ge a promising candidate for the device of topological spintronics.

Magnetic and spin transport properties of a two-dimensional magnetic semiconductor kagome lattice Nb<sub>3</sub>Cl<sub>8</sub> monolayer

Two-dimensional semiconductor materials with intrinsic magnetism have great application prospects in realizing spintronic devices with low power consumption, small size and high efficiency. Some two-dimensional materials with special lattice structures, such as kagome lattice crystals, are favored by researchers because of their novel properties in magnetism and electronic properties. Recently, a new two-dimensional magnetic semiconductor material Nb<sub>3</sub>Cl<sub>8</sub> monolayer with kagome lattice structure was successfully prepared, which provides a new platform for exploring two-dimensional magnetic semiconductor devices with kagome structure. In this work, we study the electronic structure and magnetic anisotropy of Nb<sub>3</sub>Cl<sub>8</sub> monolayer. We also further construct its <i>p-n</i> junction diode and study its spin transport properties by using density functional theory combined with non-equilibrium Green's function method. The results show that the phonon spectrum of the Nb<sub>3</sub>Cl<sub>8</sub> monolayer has no negative frequency, confirming its dynamic stability. The band gap of the spin-down state (1.157 eV) is significantly larger than that of the spin-up state (0.639 eV). The magnetic moment of the Nb<sub>3</sub>Cl<sub>8</sub> monolayer is 0.997 μ<sub>B</sub>, and its easy magnetization axis is in the plane and along the <i>x</i> axis direction based on its energy of magnetic anisotropy. Nb atoms make the main contribution to the magnetic anisotropy. When the strain is applied, the band gap of the spin-down states will decrease, while the band gap of the spin-up state is monotonously decreased from the negative (compress) to positive (tensile) strain. As the strain variable goes from -6% to 6%, the contribution of Nb atoms to the total magnetic moment gradually increases. Moreover, strain causes the easy magnetization axis of the Nb<sub>3</sub>Cl<sub>8</sub> monolayer to flip vertically from in-plane to out-plane. The designed <i>p-n</i> junction diode nanodevice based on Nb<sub>3</sub>Cl<sub>8</sub> monolayer exhibits an obvious rectification effect. In addition, the current in the spin-up state is larger than that in the spin-down state, exhibiting a spin-polarized transport behavior. Moreover, a negative differential resistance (NDR) phenomenon is also observed, which could be used in the NDR devices. These results demonstrate that the Nb<sub>3</sub>Cl<sub>8</sub> monolayer material has great potential application in the next generation of high-performance spintronic devices, and further experimental verification and exploration of this material and related two-dimensional materials are needed.

Magnetic and spin transport properties of a two-dimensional magnetic semiconductor kagome lattice Nb<sub>3</sub>Cl<sub>8</sub> monolayer

Two-dimensional semiconductor materials with intrinsic magnetism have great application prospects in realizing spintronic devices with low power consumption, small size and high efficiency. Some two-dimensional materials with special lattice structures, such as kagome lattice crystals, are favored by researchers because of their novel properties in magnetism and electronic properties. Recently, a new two-dimensional magnetic semiconductor material Nb<sub>3</sub>Cl<sub>8</sub> monolayer with kagome lattice structure was successfully prepared, which provides a new platform for exploring two-dimensional magnetic semiconductor devices with kagome structure. In this work, we study the electronic structure and magnetic anisotropy of Nb<sub>3</sub>Cl<sub>8</sub> monolayer. We also further construct its <em>p-n</em> junction diode and study its spin transport properties by using density functional theory combined with non-equilibrium Green's function method. The results show that the phonon spectrum of the Nb<sub>3</sub>Cl<sub>8</sub> monolayer has no negative frequency, confirming its dynamic stability. The band gap of the spin-down state (1.157 eV) is significantly larger than that of the spin-up state (0.639 eV). The magnetic moment of the Nb<sub>3</sub>Cl<sub>8</sub> monolayer is 0.997 μ<sub>B</sub>, and its easy magnetization axis is in the plane and along the <em>x</em> axis direction based on its energy of magnetic anisotropy. Nb atoms make the main contribution to the magnetic anisotropy. When the strain is applied, the band gap of the spin-down states will decrease, while the band gap of the spin-up state is monotonously decreased from the negative (compress) to positive (tensile) strain. As the strain variable goes from -6% to 6%, the contribution of Nb atoms to the total magnetic moment gradually increases. Moreover, strain causes the easy magnetization axis of the Nb<sub>3</sub>Cl<sub>8</sub> monolayer to flip vertically from in-plane to out-plane. The designed <em>p-n</em> junction diode nanodevice based on Nb<sub>3</sub>Cl<sub>8</sub> monolayer exhibits an obvious rectification effect. In addition, the current in the spin-up state is larger than that in the spin-down state, exhibiting a spin-polarized transport behavior. Moreover, a negative differential resistance (NDR) phenomenon is also observed, which could be used in the NDR devices. These results demonstrate that the Nb<sub>3</sub>Cl<sub>8</sub> monolayer material has great potential application in the next generation of high-performance spintronic devices, and further experimental verification and exploration of this material and related two-dimensional materials are needed.

Meta-Kagome lattice structures for broadband vibration isolation

One-dimensional (1D) phononic crystal (PC) beams have been extensively studied due to their bandgap properties, but the idea of using this functional beam components to form three-dimensional (3D) periodic structures has rarely been mentioned. In this paper, the PC beam element is used to replace the ordinary member of the conventional Kagome lattice structures, thus, a meta-Kagome lattice (MKL) structure is innovatively constructed with broadband vibration isolation performance. The dispersion analysis is performed to reveal the mechanism of bandgap formation and the reason of getting broad bandgaps. Three kinds of MKL structures, namely, with triangular, rectangular and hexagonal pyramids are designed. The vibration transmission properties of the MKL columns with or without interfaces are studied to illustrate the isolation effect. Moreover, the vibration isolation performance of the sandwich structures composed of MKL cores is also studied, and the influence of the skin characteristics on the properties is discussed. Vibration transmission tests were conducted to verify the results. This work provides a new method to develop 3D multi-functional lattice structures, especially for load-bearing and vibration reduction.

On Quasi-Static and Dynamic Compressive Behaviors of Interlocked Composite Kagome Lattice Structures

Abstract The quasi-static and dynamic compressive behaviors of carbon fiber-reinforced plastic (CFRP) Kagome lattice structures subjected to quasi-static load and low-velocity impact were investigated experimentally and numerically. CFRP Kagome lattice structures were fabricated by using the interlocking method. The quasi-static compression and low-velocity impact experiments were carried out and the failure mechanisms of CFRP Kagome lattice structures were explored. A user-defined material subroutine (VUMAT) involving three-dimensional Hashin criterion and progressive damage evolution was developed and implemented in the refined finite element (FE) model to model the failure of composite lattice structures. Good agreement is achieved between FE simulations and experimental results. It is shown that both in-plane stiffness and the failure mode of CFRP Kagome lattice structure are sensitive to the load directions. CFRP Kagome lattice structures subjected to quasi-static load experience elastic deformation, bending/kinking failure, rib fracture, and structure collapse sequentially. CFRP Kagome lattice structures subjected to low-velocity impact suffer from the multiple fractures at the slots and the maximum peak loads of dynamic response increase with increasing the impact velocity.

Realization of Photonic Topological Insulators at Terahertz Frequencies Characterized by Time-Domain Spectroscopy

Topological systems are inherently robust to disorder and continuous perturbations, resulting in dissipation-free edge transport of electrons in quantum solids, or reflectionless guiding of photons and phonons in classical wave systems characterized by topological invariants. Realization of robust, lossless topological insulators in the technologically important terahertz (THz) frequency range has drawn immense attention. In this paper, we propose a Kagome lattice structure that supports topological edge states with valley-dependent transport. Optical topological insulators are subsequently fabricated, in which mirror symmetry is broken and degenerate states are lifted at $K({K}^{\ensuremath{'}})$ valleys in the band structure. Theoretical and numerical analyses show that four types of edge states can be obtained. The performance of the fabricated topological waveguides is characterized with THz time-domain spectroscopy (TDS). Nearly identical THz wave transmission in the 0.437--0.453-THz range is verified with a straight-line topological waveguide and Z-shaped waveguides with multiple sharp turning corners, which quantitatively illustrate the strong backscattering suppression effects from the nontrivial topology edge states of the structures. Particularly, the THz TDS measurements provide important extra time-domain information about the topological waveguiding mode, which is generally unavailable from previous topological insulator investigations solely replying on power spectrum measurements.

Evidence of ferromagnetic clusters in magnetic Weyl semimetal Co3Sn2S2

Cobalt based sulfides of compositional formula Co3A2S2 (A = Sn and In) are endowed with frustrated kagome lattice structure and a plethora of novel phenomena due to the topological band structure. We report on the detailed exploration of magnetic properties of single crystals of ferromagnetic Weyl semimetal Co3Sn2S2. A non-linear behaviour observed in the inverse susceptibility above the critical temperature TC in the paramagnetic state corroborates to the presence of short-range ferromagnetic clusters above TC in Co3Sn2S2. The upward deviation indicates the antiferromagnetic interactions between the nearest neighbouring magnetic clusters. The slow spin dynamics behaviour above TC in isothermal remanent magnetization provide another evidence of ferromagnetic clusters. The magnetic hysteresis loops represent the magnetization reversal which, in turn, also confirm the short range magnetic correlations. Further, non-linear isothermal magnetization curves and zero spontaneous magnetization derived from corresponding Arrott plots above TC prove the short range ferromagnetic clusters in Co3Sn2S2. Our experimental results emphasize an intuitive understanding of the complex nature of magnetism present in Co-based shandite systems.

Coexistence of two intertwined charge density waves in a kagome system

Materials with a kagome lattice structure display a wealth of intriguing magnetic properties due to their geometric frustration and intrinsically flat band structure. Recently, topological and superconducting states have also been observed in kagome systems. The kagome lattice may also host a ``breathing'' mode that leads to charge density wave (CDW) states, if there is strong electron-phonon coupling, electron-electron interaction, or external excitation of the material. This ``breathing'' mode can give rise to candidate distortions such as the star of David (SoD) or its inverse structure [trihexagonal (TrH)]. To date, in most materials, only a single type of distortion has been observed. Here, we present angle-resolved photoemission spectroscopy measurements on the kagome superconductor ${\mathrm{CsV}}_{3}{\mathrm{Sb}}_{5}$ at multiple temperatures and photon energies to reveal the nature of the CDW in this material. It is shown that ${\mathrm{CsV}}_{3}{\mathrm{Sb}}_{5}$ displays two intertwined CDW orders corresponding to the SoD and TrH distortions. These two distinct types of distortions are stacked along the $c$ direction to form a three-dimensional CDW order where the two 2-fold CDWs are phase shifted along the $c$ axis. The presented results provide not only key insights into the nature of the unconventional CDW order in ${\mathrm{CsV}}_{3}{\mathrm{Sb}}_{5}$, but also an important reference for further studies on the relationship between the CDW and superconducting order.

Electron-phonon coupling in the charge density wave state of CsV3Sb5

Metallic materials with kagome lattice structure are interesting because their electronic structures can host flat bands, Dirac cones, and van Hove singularities, resulting in strong electron correlations, nontrivial band topology, charge density wave (CDW), and unconventional superconductivity. Recently, kagome lattice compounds AV$_3$Sb$_5$ (A = K, Rb, Cs) are found to have intertwined CDW order and superconductivity. The origin of the CDW has been suggested to be purely electronic, arising from Fermi-surface instabilities of van Hove singularity (saddle point) near the M points. Here we use neutron scattering experiments to demonstrate that the CDW order in CsV$_3$Sb$_5$ is associated with static lattice distortion and a sudden hardening of the B3u longitudinal optical phonon mode, thus establishing that electron-phonon coupling must also play an important role in the CDW order of AV$_3$Sb$_5$.

Energy absorption structures with soft surface based on topological mechanics

In energy absorption structures, soft and hard mechanical properties need to be varied to enhance impact mitigation. Topological mechanics have potential to achieve the varying properties in structures by periodic arrangements. This study designs the energy absorption of kagome lattice structures whose mechanisms (i.e., floppy modes) are localized on surface based on topological mechanics to soften the contact surface. As a result of numerical simulation of the lattice structure, peak of the force-displacement curve is suppressed during compression by rigid cylinder, which indicates that localized mechanisms provide soft surface on energy absorption structures.