arXiv subjects

Takehito Suzuki

Publications and source records attributed to Takehito Suzuki.

At least 19 recordsLinked to original sources

arXiv2025

XY-like Incommensurate Magnetic Order in Ce$_2$SnS$_5$

We report the synthesis of single crystals of Ce$_2$SnS$_5$ through a two-stage chemical vapor transport method. The Ce$_2$SnS$_5$ system is a member of the orthorhombic $Pbam$ (No. 55) space group and realizes a distorted trigonal tricapped prism (TTP) crystal field around each cerium site. We characterized the sample through orientation-dependent magnetization and heat capacity measurements to probe the magnetic anisotropy in the system characteristic of XY-like anisotropic Heisenberg model behavior. Ce$_2$SnS$_5$ furthermore enters a zero-field ordered phase under $T_N =$ 2.4 K; powder neutron diffraction measurements reveal incommensurate magnetic order near $T_N$. The system then locks into a commensurate, two-$q$ magnetic structure below approximately 1.2 K. This commensurate structure belongs to the Shubnikov group $Pb'a'm'$ (MSG 55.359) and realizes the propagation vectors $\vec{q} = (1/3,0,0)$ and $\vec{q} = (0,0,0)$.

cond-mat.mes-hall↗

arXiv2025

Higher-dimensional Fermiology in bulk moiré metals

In the past decade, moiré materials have revolutionized how we engineer and control quantum phases of matter. Among incommensurate materials, moiré materials are aperiodic composite crystals whose long-wavelength moiré superlattices enable tunable properties without chemically modifying their layers. To date, nearly all reports of moiré materials have investigated van der Waals heterostructures assembled far from thermodynamic equilibrium. Here we introduce a conceptually new approach to synthesizing high-mobility moiré materials in thermodynamic equilibrium. We report a new family of foliated superlattice materials (Sr$_6$TaS$_8$)$_{1+δ}$(TaS$_2$)$_8$ that are exfoliatable van der Waals crystals with atomically incommensurate lattices. Lattice mismatches between alternating layers generate moiré superlattices, analogous to those of 2D moiré heterobilayers, that are coherent throughout these crystals and are tunable through their synthesis conditions without altering their chemical composition. High-field quantum oscillation measurements map the complex Fermiology of these moiré metals, which can be tuned via the moiré superlattice structure. We find that the Fermi surface of the structurally simplest moiré metal is comprised of over 40 distinct cross-sectional areas, the most observed in any material to our knowledge. This can be naturally understood by postulating that bulk moiré materials can encode electronic properties of higher-dimensional superspace crystals in ways that parallel well-established crystallographic methods used for incommensurate lattices. More broadly, our work demonstrates a scalable synthesis approach potentially capable of producing moiré materials for electronics applications and evidences a novel material design concept for accessing a broad range of physical phenomena proposed in higher dimensions.

cond-mat.mtrl-sci↗

arXiv2025

Anisotropic Magnetism in Gd$_2$B$_5$

We report the synthesis of single crystals of Gd$_2$B$_5$ through a ruthenium-gadolinium flux method. The Gd$_2$B$_5$ system is a member of the monoclinic $P21/c$ (No. 14) space group and realizes lattices of gadolinium atoms in the $(1\,0\,0)$ plane. We characterized the sample through orientation-dependent electrical transport, magnetization, magnetic torque, and heat capacity measurements to probe the magnetic anisotropy of the system and map out its phase diagram. Gd$_2$B$_5$ realizes two zero-field ordered phases M$_1$ and M$_2$, as well as a third field-induced ordered phase M$_\perp$ arising when the magnetic field is applied in the $(1\,0\,0)$ plane.

cond-mat.mes-hall↗

arXiv2025

Self-organized first-order transition from foreshock to mainshock in earthquake sequences induced by heat, fluid pressure, and porosity

Earthquake cycles are studied by taking into account the interactions among slip, fluid pressure, temperature, and porosity on the fault planes, which are known to play a crucial role in earthquake dynamics. The spring-block model with a single block is employed. A first-order transition from foreshock to mainshock occurring spontaneously in earthquake sequences is discovered both analytically and numerically. This transition is induced by these interactions. It is shown that the function of the slip distance $u$, $F(u)$, defined as the sum of the difference between the energies stored in the driving spring before and after the slippage, and the energy dissipated during the slippage, governs the transition. The equation, $F(u)=0$, represents the energy balance before and after the slippage, and the solution $u=u_f$ describes the realized slip distance for each slippage event. The solutions discontinuously transition from small to large slippages in the sequence of earthquakes. This transition can be interpreted to be a self-organized first-order transition from small to large slippages. The former slippage is governed by pore generation, whereas the latter is governed by thermal pressurization. A phase diagram of the foreshocks and mainshocks, which is also considered a phase diagram of slow and fast earthquakes, is obtained.

cond-mat.mtrl-sci↗

arXiv2025

Anomalous Order in $R_3\text{Ni}_{30}\text{B}_{10}$ $(R = \text{La}, \text{Ce})$

We report the synthesis of single crystals of the $R_3\text{Ni}_{30}\text{B}_{10}$ $(R = \text{La}, \text{Ce})$ system which realizes the tetragonal $P4/nmm$ (No. 129) space group. We performed single crystal, transmission X-ray diffraction measurements to determine the crystal structure. Additionally, we characterized the samples through magnetization, resistivity, and heat capacity measurements. The $R = \text{Ce}$ system exhibits mixed-valence states and we observe maxima in the heat capacity at $T_1^* = 6 \, \text{K}$ and $T_2^* = 2 \, \text{K}$ (both absent for $R = \text{La}$) with no corresponding features in the resistivity or magnetization. We discuss the potential roles of multipolar and short-ranged/partial order in connection to the $T_1^*$ anomalous order.

cond-mat.mes-hall↗

arXiv2024

Striped electronic phases in an incommensurately modulated van der Waals superlattice

Electronic properties of crystals can be manipulated using spatially periodic modulations. Long-wavelength, incommensurate modulations are of particular interest, exemplified recently by moiré patterned van der Waals (vdW) heterostructures. Bulk vdW superlattices hosting interfaces between clean 2D layers represent scalable bulk analogs of vdW heterostructures and present a complementary venue to explore incommensurately modulated 2D states. Here we report the bulk vdW superlattice SrTa$_2$S$_5$ realizing an incommensurate 1D modulation of 2D transition metal dichalcogenide (TMD) $H$-TaS$_2$ layers. High-quality electronic transport in the $H$-TaS$_2$ layers, evidenced by quantum oscillations, is made anisotropic by the modulation and shows commensurability oscillations akin to lithographically modulated 2D systems. We also find unconventional, clean-limit superconductivity (SC) in SrTa$_2$S$_5$ with a pronounced suppression of interlayer coherence relative to intralayer coherence. Such a hierarchy can arise from pair-density wave (PDW) SC with mismatched spatial arrangement in adjacent superconducting layers. Examining the in-plane magnetic field $H_{ab}$ dependence of interlayer critical current density $J_c$, we find anisotropy with respect to $H_{ab}$ orientation: $J_c$ is maximized (minimized) when $H_{ab}$ is perpendicular (parallel) to the stripes, consistent with 1D PDW SC. From diffraction we find the structural modulation is shifted between adjacent $H$-TaS$_2$ layers, suggesting mismatched 1D PDW is seeded by the striped structure. With a high-mobility Fermi liquid in a coherently modulated structure, SrTa$_2$S$_5$ is a promising host for novel phenomena anticipated in clean, striped metals and superconductors. More broadly, SrTa$_2$S$_5$ establishes bulk vdW superlattices as macroscopic platforms to address long-standing predictions for modulated electronic phases.

cond-mat.mtrl-sci↗

arXiv2022

Deriving the slip front propagation velocity with the slip- and slip-velocity-dependent friction laws via the use of the linear marginal stability hypothesis

We analytically and numerically investigate the determining factors of the slip front propagation (SFP) velocity. The slip front has two forms characterized by intruding or extruding front. We assume a 1D viscoelastic medium on a rigid and fixed substrate, and we employ the friction law depending on the slip and slip velocity. Despite this dependency potentially being nonlinear, we use the linear marginal stability hypothesis, which linearizes the governing equation for the slip, to investigate the intruding and extruding front velocities. The analytically obtained velocities are found to be consistent with the numerical computation where we assume the friction law nonlinearly depends on both the slip and slip velocity. This implies that the linearized friction law is sufficient to capture the dominant features of SFP behavior.

cond-mat.other↗

arXiv2022

Band Structure Driven Thermoelectric Response of Topological Semiconductor ZrTe$_5$

We report a transport, thermodynamic, and spectroscopic study of the recently identified topological semiconductor ZrTe$_5$ with a focus on elucidating the connections between its band structure and unusual thermoelectric properties. Using time and angle resolved photoemission spectroscopy (tr-ARPES) we observe a small electronic band gap and temperature dependent Fermi level which traverses from a single valence to conduction band with lowering temperature, consistent with previous reports. This low temperature Fermi surface closely matches that derived from quantum oscillations, suggesting it is reflective of the bulk electronic structure. The Seebeck and low field Nernst response is characterized by an unusually large and non-monotonic temperature evolution. We find this can be quantitatively explained using a semiclassical model based on the observed band character and a linear temperature shifting of the Fermi level. Additionally, we observe a large, non-saturating enhancement of both thermoelectric coefficients in magnetic field. We show this can be captured by the Zeeman energy associated with a large effective $g$-factor of 25.8 consistent with that derived from Lifshitz-Kosevich analysis of the quantum oscillations. Together these observations provide a comprehensive picture of ZrTe$_{5}$ as a model high mobility semiconductor and potential platform for significant magnetic field driven thermoelectricity.

cond-mat.mtrl-sci↗

arXiv2020

Characteristic Sensitivity of Turbulent Flow within a Porous Medium under Initial Conditions

Flows within porous media play important roles in many scientific and industrial systems. However, the case wherein such flows become turbulent has not been completely understood, particularly, from a mathematical viewpoint. In this study, the $k-\varepsilon$ model (the variable $k$ denotes the turbulent kinetic energy per unit mass and $\varepsilon$ the dissipation rate for the turbulent kinetic energy), which has been widely used for the usual turbulent flow in a clear fluid, was applied to a turbulent flow through porous media. If a homogeneous, averaged flow and homogeneous isotropic turbulence are assumed, the governing equations for the variables $k$ and $\varepsilon$ describe a straight line as a nullcline common to both the variables. The nullcline was shown to be a line attractor. A temporal evolution of the eddy viscosity was also obtained, and the initial and final values of the eddy viscosity were observed to be related to a power law, indicating universal sensitivity. This sensitivity originates from the common nullcline and is not observed for the usual turbulent flow. Finally, nonlinear mathematical and seismological implications were provided using based on the results obtained.

physics.flu-dyn↗

arXiv2020

Clean 2D superconductivity in a bulk van der Waals superlattice

Advances in low-dimensional superconductivity are often realized through improvements in material quality. Apart from a small group of organic materials, there is a near absence of clean-limit two-dimensional (2D) superconductors, which presents an impediment to the pursuit of numerous long-standing predictions for exotic superconductivity with fragile pairing symmetries. Here, we report the development of a bulk superlattice consisting of the transition metal dichalcogenide (TMD) superconductor 2$H$-niobium disulfide (2$H$-NbS$_2$) and a commensurate block layer that yields dramatically enhanced two-dimensionality, high electronic quality, and clean-limit inorganic 2D superconductivity. The structure of this material may naturally be extended to generate a distinct family of 2D superconductors, topological insulators, and excitonic systems based on TMDs with improved material properties.

cond-mat.supr-con↗

arXiv2019

Spectromicroscopic measurement of surface and bulk band structure interplay in a disordered topological insulator

Topological insulators are bulk semiconductors that manifest in-gap massless Dirac surface states due to the topological bulk-boundary correspondence principle [1-3]. These surface states have been a subject of tremendous ongoing interest, due both to their intrinsic properties and to higher order emergence phenomena that can be achieved by manipulating the interface environment [4-11]. Here, angle resolved photoemission (ARPES) spectromicroscopy and supplementary scanning tunneling microscopy (STM) are performed on the model topological insulator Bi2Se3 to investigate the interplay of crystallographic inhomogeneity with the topologically ordered bulk and surface band structure. Quantitative analysis methods are developed to obtain key spectroscopic information in spite of a limited dwell time on each measured point. Band energies are found to vary on the scale of 50 meV across the sample surface, enabling single-sample measurements that are analogous to a multi-sample doping series (termed a "binning series"). Focusing separately on the surface and bulk electrons reveals a nontrivial hybridization-like interplay between fluctuations in the surface and bulk state energetics.

cond-mat.mtrl-sci↗

arXiv2019

Transition between Macroscopic Steady Slippage and Creep Motion in a System with Velocity-Dependent Friction Stress

We investigate the propagation of a slip front in a visco-elastic body on a rigid substrate. The body is one-dimensional, and the loading stress is applied at one end. By employing a local friction law that has a quadratic form of the slip velocity and gives vanishing friction stress at vanishing velocity or above a certain velocity, we show analytically that macroscopic steady slippage and creep motion can be understood in a single framework. The critical values of the end-loading stress causing macroscopic steady slippage and the slip-front propagation velocity appear are obtained. These values are completely determined by the gradient of the slip velocity-friction curve at the vanishing friction stress. These results are extended to more general friction laws, and found to be consistent with numerical calculations. Furthermore, we discuss some seismological implications based on the analytical and numerical results.

physics.flu-dyn↗

arXiv2019

Molecular Beam Epitaxy Growth of Antiferromagnetic Kagome Metal FeSn

FeSn is a room-temperature antiferromagnet expected to host Dirac fermions in its electronic structure. The interplay of magnetic degree of freedom and the Dirac fermions makes FeSn an attractive platform for spintronics and electronic devices. While stabilization of thin film FeSn is needed for the development of such devices, there exist no previous report of epitaxial growth of single crystalline FeSn. Here we report the realization of epitaxial thin films of FeSn (001) grown by molecular beam epitaxy on single crystal SrTiO$_{3}$ (111) substrates. By combining X-ray diffraction, electrical transport, and torque magnetometry measurements, we demonstrate the high quality of these films with the residual resistivity ratio $ρ_{xx}(300 \hspace{0.2em}{\rm K})/ρ_{xx}(2 \hspace{0.2em}{\rm K}) = 24$ and antiferromagnetic ordering at $T_{\rm N}$ = 353 K. These developments open a pathway to manipulate the Dirac fermions in FeSn by both magnetic interactions and the electronic field effect for use in antiferromagnetic spintronics devices.

cond-mat.str-el↗

arXiv2019

Band engineering of a magnetic thin film rare earth monopnictide

Realizing quantum materials in few atomic layer morphologies is a key to both observing and controlling a wide variety of exotic quantum phenomena. This includes topological electronic materials, where the tunability and dimensionality of few layer materials have enabled the detection of $Z_2$, Chern, and Majorana phases. Here, we report the development of a platform for thin film correlated, topological states in the magnetic rare-earth monopnictide ($RX$) system GdBi synthesized by molecular beam epitaxy. This material is known from bulk single crystal studies to be semimetallic antiferromagnets with Neel temperature $T_N =$ 28 K and is the magnetic analog of the non-$f$-electron containing system LaBi proposed to have topological surface states. Our transport and magnetization studies of thin films grown epitaxially on BaF$_2$ reveal that semimetallicity is lifted below approximately 8 crystallographic unit cells while magnetic order is maintained down to our minimum thickness of 5 crystallographic unit cells. First-principles calculations show that the non-trivial topology is preserved down to the monolayer limit, where quantum confinement and the lattice symmetry give rise to a $C=2$ Chern insulator phase. We further demonstrate the stabilization of these films against atmospheric degradation using a combination of air-free buffer and capping procedures. These results together identify thin film $RX$ materials as potential platforms for engineering topological electronic bands in correlated magnetic materials.

cond-mat.str-el↗

arXiv2018

de Haas-van Alphen effect of correlated Dirac states in kagome metal Fe3Sn2

The field of topological electronic materials has seen rapid growth in recent years, in particular with the increasing number of weakly interacting systems predicted and observed to host topologically non-trivial bands. Given the broad appearance of topology in such systems, it is expected that correlated electronic systems should also be capable of hosting topologically non-trivial states. Interest in correlated platforms is heightened by the prospect that collective behavior therein may give rise to new types of topological states and phenomena not possible in non-interacting systems. However, to date only a limited number of correlated topological materials have been definitively reported due to both the challenge in calculation of their electronic properties and the experimental complexity of correlation effects imposed on the topological aspects of their electronic structure. Here, we report a de Haas-van Alphen (dHvA) study of the recently discovered kagome metal Fe$_3$Sn$_2$ mapping the massive Dirac states strongly coupled to the intrinsic ferromagnetic order. We observe a pair of quasi-two-dimensional Fermi surfaces arising from the massive Dirac states previously detected by spectroscopic probes and show that these band areas and effective masses are systematically modulated by the rotation of the ferromagnetic moment. Combined with measurements of Berry curvature induced Hall conductivity, we find that along with the Dirac fermion mass, velocity, and energy are suppressed with rotation of the moment towards the kagome plane. These observations demonstrate that strong coupling of magnetic order to electronic structure similar to that observed in elemental ferromagnets can be extended to topologically non-trivial electronic systems, suggesting pathways for connecting topological states to robust spintronic technologies.

cond-mat.str-el↗

arXiv2018

Observation of a Topological Insulator Dirac Cone Reshaped by Non-magnetic Impurity Resonance

The massless Dirac electrons found at topological insulator surfaces are thought to be influenced very little by weak, non-magnetic disorder. However, a resonance effect of strongly perturbing non-magnetic impurities has been theoretically predicted to change the dispersion and physical nature of low-energy quasiparticles, resulting in unique particle-like states that lack microscopic translational symmetry. Here we report the direct observation of impurities reshaping the surface Dirac cone of the model 3D topological insulator Bi2Se3. For the first time, a pronounced kink-like dispersion feature is observed in disorder-enriched samples, and found to be closely associated with the anomaly caused by impurity resonance in the surface state density of states, as observed by dichroic angle resolved photoemission spectroscopy (ARPES). The experimental observation of these features, which closely resemble theoretical predictions, has significant implications for the properties of topological Dirac cones in applied scenarios that commonly feature point defect disorder at surfaces or interfaces.

cond-mat.mtrl-sci↗

arXiv2018

Propagation velocity of slip front and emergence of macroscopic static friction in the system with vanishing local static friction

We investigate the propagation of the slip front in the elastic body on the rigid substrate. We first obtain the slip profile and the slip front velocity of the steady state by employing the local friction law with the quadratic form of the slip velocity and with vanishing static friction stress. The macroscopic static friction stress emerges spontaneously, which is expressed in terms of the parameter emerging in the friction law. For the model with viscosity, the macroscopic static friction stress again emerges spontaneously. The analytical treatment gives estimations for two slip front propagation velocities. They corresponds to two different boundary conditions, and one of them describes the framework employed here. Linear Marginal Stability Hypothesis based on the linearized equation of motion shows that two slip front propagation velocities exist in this system, both of which coincide with the analytical solutions noted above. These imply that the linearized friction law dominantly governs the slip front propagation behavior. Seismological implications are also given based on the analytical and numerical results.

cond-mat.soft↗

arXiv2017

Massive Dirac fermions in a ferromagnetic kagome metal

The kagome lattice is a two-dimensional network of corner-sharing triangles known as a platform for exotic quantum magnetic states. Theoretical work has predicted that the kagome lattice may also host Dirac electronic states that could lead to topological and Chern insulating phases, but these have evaded experimental detection to date. Here we study the d-electron kagome metal Fe$_3$Sn$_2$ designed to support bulk massive Dirac fermions in the presence of ferromagnetic order. We observe a temperature independent intrinsic anomalous Hall conductivity persisting above room temperature suggestive of prominent Berry curvature from the time-reversal breaking electronic bands of the kagome plane. Using angle-resolved photoemission, we discover a pair of quasi-2D Dirac cones near the Fermi level with a 30 meV mass gap that accounts for the Berry curvature-induced Hall conductivity. We show this behavior is a consequence of the underlying symmetry properties of the bilayer kagome lattice in the ferromagnetic state with atomic spin-orbit coupling. This report provides the first evidence for a ferromagnetic kagome metal and an example of emergent topological electronic properties in a correlated electron system. This offers insight into recent discoveries of exotic electronic behavior in kagome lattice antiferromagnets and may provide a stepping stone toward lattice model realizations of fractional topological quantum states.

cond-mat.mtrl-sci↗