arXiv subjects

Yasuhiro H. Matsuda

Publications and source records attributed to Yasuhiro H. Matsuda.

At least 37 records · Page 2Linked to original sources

arXiv2024

Geometric frustration and Dzyaloshinskii-Moriya interactions in a quantum star lattice hybrid copper sulfate

We study the magnetism of a layered, spin-$\frac12$ organic-inorganic copper sulfate, which is a close realization of the star lattice antiferromagnet, one of the playgrounds of geometric frustration and resonating valence bond physics in two spatial dimensions. Our thermodynamic measurements show no ordering down to 0.1 K and a characteristic field-induced entropic shift, revealing the presence of an infinite number of competing states down to very low energy scales. The response to external magnetic fields shows, in addition, a peculiar anisotropy, reflected in the formation of a 1/3 magnetization plateau (stable up to full saturation around 105 T) and a paramagnetic, Curie-like susceptibility for one direction of the field (${\bf H}\parallel{\bf c}$), and a completely different response in other field directions. Our first-principles density functional theory calculations and exact diagonalizations show that these experimental puzzles are distinctive signatures of a strong interplay between geometric frustration and sizable Dzyaloshinskii-Moriya interactions, and the emergence of a continuous U(1) symmetry at low energy scales.

cond-mat.str-el↗

arXiv2023

Possible Intermediate Quantum Spin Liquid Phase in $α$-RuCl$_3$ under High Magnetic Fields up to 100 T

Pursuing the exotic quantum spin liquid (QSL) state in the Kitaev material $α$-RuCl$_3$ has intrigued great research interest recently. A fascinating question is on the possible existence of field-induced QSL phase in this compound. Here we perform a high-field measurement of the magnetization process of $α$-RuCl$_3$ up to 102 T employing the non-destructive and destructive pulsed magnets. Under the out-of-plane field along the c$^*$ axis (i.e., perpendicular to the honeycomb plane), two quantum phase transitions are uncovered at respectively 36 T and about 83 T, between which there lies an intermediate phase as the predicted QSL. By measuring the magnetization data with fields tilted from the c$^*$ axis up to $90^\circ$ (i.e., in-plane direction), we obtain the field-angle phase diagram that contains the zigzag, paramagnetic, and QSL phases. Based on the accurate $K$-$J$-$Γ$-$Γ^{\prime}$ model of $α$-RuCl$_3$, we perform density matrix renormalization group simulations and reproduce the quantum phase diagram in excellent agreement with experiments.

cond-mat.str-el↗

arXiv2023

Signature of spin-triplet exciton condensations in LaCoO$_{3}$ at ultrahigh magnetic fields up to 600 T

Bose-Einstein condensation of electron-hole pairs, exciton condensation, has been effortfully investigated since predicted 60 years ago. Irrefutable evidence has still been lacking due to experimental difficulties in verifying the condensation of the charge neutral and non-magnetic spin-singlet excitons. Whilst, condensation of spin-triplet excitons is a promising frontier because spin supercurrent and spin-Seebeck effects will be observable. A canonical cobaltite LaCoO$_{3}$ under very high magnetic fields is a propitious candidate, yet to be verified. Here, we unveil the exotic phase diagram of LaCoO$_{3}$ up to 600 T generated using the electromagnetic flux compression method and the state-of-the-art magnetostriction gauge. We found the continuous magnetostriction curves and a bending structure, which suggest the emergence of two distinct spin-triplet exciton condensates. By constructing a phenomenological model, we showed that quantum fluctuations of excitons are crucial for the field-induced successive transitions. The spin-triplet exciton condensation in a cobaltite, which is three-dimensional and thermally equilibrated, opens up a novel venue for spintronics technologies with spin-supercurrent such as a spin Josephson junction.

cond-mat.str-el↗

arXiv2022

Ferroelectric transition of a chiral molecular crystal BINOL2DMSO

We report dielectric, thermodynamical, acoustic, and optical properties of a chiral molecular crystal, 1,1'-bi-2-naphthol 2-dimethylsulfoxide (BINOL2DMSO). We find two successive phase transitions at Tc1=190 K and Tc2=125 K. The first transition at Tc1 is characterized by an order-disorder transition of the guest molecules DMSO along with ferroelectricity. At the second transition of Tc2, the crystal structure deforms from tetragonal to monoclinic, leading to domain formation. Low-temperature x-ray diffraction suggests that the space group changes from P4_12_12 (P4_32_12) to P4_1 (P4_3) at Tc1, and down to P112_1 at Tc2.

cond-mat.mtrl-sci↗

arXiv2022

Generating 77 T using a portable pulse magnet for single shot quantum beam experiments

We devised a portable system that generates pulsed high magnetic fields up to 77 T with 3 $μ$s duration. The system employs the single turn coil method, a destructive way of field generation. The system consists of a capacitor of 10.4 $μ$F, a 30 kV charger, a mono air-gap switch, a triggering system, and a magnet clamp, which weighs less than 1.0 tons in total and is transportable. The system offers opportunities for single-shot experiments at ultrahigh magnetic fields in combinations with novel quantum beams. The single-shot x-ray diffraction experiment using x-ray free-electron laser at 65 T is presented. We comment on the possible update of the system for the generation of 100 T.

cond-mat.str-el↗

arXiv2021

Phase transition in the 5d1 double perovskite Ba2CaReO6 induced by high magnetic field

Magnetic properties of an antiferromagnetic double perovskite oxide Ba2CaReO6, where Re6+ (5d1) ions with large spin-orbit coupling are arranged on the face-centered-cubic lattice, are investigated using pulsed high magnetic field up to 66 T. Magnetization and magnetostriction measurements have revealed a magnetic field induced phase transition at around 50 T. The phase transition accompanies a jump of magnetization and longitudinal magnetostriction of approximately 2 10^(-4) with the change of power law behavior, indicating sizable coupling between the electronic degrees of freedom and the lattice. The high field phase exhibits a magnetic moment approximately 0.2 μB, which is close to the values observed in 5d1 double perovskite oxides with non-collinear magnetic structure. We argue that Ba2CaReO6 is an antiferromagnet that sits close to the phase boundary between the collinear and non-collinear phases, providing the target material for investigating the interplay between spin-orbital entangled electrons and magnetic field.

cond-mat.str-el↗

arXiv2020

Two Spin-State Crystallizations in LaCoO$_{3}$

We report a magnetostriction study of a perovskite $\rm{LaCoO}_{3}$ above 100 T using our state-of-the-art strain gauge to investigate an interplay between electron correlations and spin crossover. There has been a controversy regarding whether two novel phases in $\rm{LaCoO}_{3}$ at high magnetic fields result from crystallizations or Bose-Einstein condensation during spin crossover as manifestations of localization and delocalization in spin states, respectively. We show that both phases are crystallizations rather than condensations, and the two crystallizations are different, based on the observations that the two phases exhibit as magnetostriction plateaux with distinct heights. The crystallizations of spin states have emerged manifesting the localizations and interactions in spin crossover with large and cooperative lattice changes.

cond-mat.str-el↗

arXiv2020

Single shot x-ray diffractometry in SACLA with pulsed magnetic fields up to 16 T

Single shot x-ray diffraction (XRD) experiments have been performed with a x-ray free electron laser (XFEL) under pulsed high magnetic fields up to 16 T generated with a nondestructive minicoil. The antiferromagnetic insulator phase in a perovskite manganaite, Pr$_{0.6}$Ca$_{0.4}$MnO$_{3}$, is collapsed at a magnetic field of $\approx 8$ T with an emergence of the ferromagnetic metallic phase, which is observed via the accompanying lattice changes in a series of the single shot XRD. The feasibility of the single shot XRD experiment under ultrahigh magnetic fields beyond 100 T is discussed, which is generated with a portable destructive pulse magnet.

cond-mat.mtrl-sci↗

arXiv2020

Experimental Measurements of Effective Mass in Near Surface InAs Quantum Wells

Near surface indium arsenide quantum wells have recently attracted a great deal of interest since they can be interfaced epitaxially with superconducting films and have proven to be a robust platform for exploring mesoscopic and topological superconductivity. In this work, we present magnetotransport properties of two-dimensional electron gases confined to an indium arsenide quantum well near the surface. The electron mass extracted from the envelope of the Shubnikov-de Haas oscillations shows an average effective mass $m^{*}$ = 0.04 at low magnetic field. Complementary to our magnetotransport study, we employed cyclotron resonance measurements and extracted the electron effective mass in the ultra high magnetic field regime. Our measurements show that the effective mass depends on magnetic field in this regime. The data can be understood by considering a model that includes non-parabolicity of the indium arsenide conduction bands.

cond-mat.mes-hall↗

arXiv2020

Magnetic-field-induced insulator-metal transition in W-doped VO2 at 500 T

Metal-insulator (MI) transitions in correlated electron systems have long been a central and controversial issue in material science. Vanadium dioxide (VO2) exhibits a first-order MI transition at 340 K. For more than half a century, it has been debated whether electronic correlation or the structural instability due to dimerised V ions is the more essential driving force behind this MI transition. Here, we show that an ultrahigh magnetic field of 500 T renders the insulator phase of tungsten (W)-doped VO2 metallic. The spin Zeeman effect on the d electrons of the V ions dissociates the dimers in the insulating phase, resulting in the delocalisation of electrons. Because the Mott-Hubbard gap essentially does not depend on the spin degree of freedom, the structural instability is likely to be the more essential driving force behind the MI transition.

cond-mat.str-el↗

arXiv2019

Magnetoelastic couplings in the deformed Kagomé quantum spin lattice of volborthite

Microscopic spin interactions on a deformed Kagomé lattice of volborthite are investigated through magnetoelastic couplings. A negative longitudinal magnetostriction $ΔL<0$ in the $b$ axis is observed, which depends on the magnetization $M$ with a peculiar relation of $ΔL/L \propto M^{1.3}$. Based on the exchange striction model, it is argued that the negative magnetostriction originates from a pantograph-like lattice change of the Cu-O-Cu chain in the $b$ axis, and that the peculiar dependence arises from the local spin correlation. This idea is supported by DFT+$U$ calculations simulating the lattice change and a finite-size calculation of the spin correlation, indicating that the recently proposed coupled-trimer model is a plausible one.

cond-mat.str-el↗

arXiv2019

Magnetostriction studies up to megagauss fields using fiber Bragg grating technique

We here report magnetostriction measurements under pulsed megagauss fields using a high-speed 100 MHz strain monitoring system devised using fiber Bragg grating (FBG) technique with optical filter method. The optical filter method is a detection scheme of the strain of FBG, where the changing Bragg wavelength of the FBG reflection is converted to the intensity of reflected light to enable the 100 MHz measurement. In order to show the usefulness and reliability of the method, we report the measurements for solid oxygen, spin-controlled crystal, and volborthite, a deformed Kagomé quantum spin lattice, using static magnetic fields up to 7 T and non-destructive millisecond pulse magnets up to 50 T. Then, we show the application of the method for the magnetostriction measurements of CaV$_{4}$O$_{9}$, a two-dimensional antiferromagnet with spin-halves, and LaCoO$_{3}$, an anomalous spin-crossover oxide, in the megagauss fields.

cond-mat.mtrl-sci↗

arXiv2018

Note: Optical filter method for high-resolution magnetostriction measurement using fiber Bragg grating under millisecond-pulsed high magnetic fields at cryogenic temperatures

High-resolution magnetostriction measurement of $ΔL/L\sim10^{-6}$ at a speed of 5 MHz is performed, using optical filter method as the detection scheme for the fiber Bragg grating (FBG) based strain monitor is performed under 35-millisecond pulsed high magnetic fields up to 45 T at 2.2 K. The resolution of magnetostriction is about the same order as the conventionally reported value from FBG based magnetostriction measurement systems for millisecond pulsed magnetic fields. The measurement speed is $\sim$100 times the conventional ones. Present system can be a faster alternative for the conventional FBG based magnetostriction measurement system for millisecond pulsed high magnetic fields.

cond-mat.mtrl-sci↗

arXiv2017

100 MHz high-speed strain monitor using fiber Bragg grating and optical filter applied for magnetostriction measurements of cobaltite at magnetic fields beyond 100 T

High-speed 100 MHz strain monitor using fiber Bragg grating (FBG) and an optical filter has been devised for the magnetostriction measurements under ultrahigh magnetic fields. The longitudinal magnetostriction of LaCoO$_{3}$ has been measured at room temperature, 115, 7 and 4.2 K up to the maximum magnetic field of 150 T. The field-induced lattice elongations are observed, which are attributed to the spin-state crossover from the low-spin ground state to excited spin-states.

cond-mat.mtrl-sci↗

arXiv2017

Magnetization process of the S = 1/2 two-leg organic spin-ladder compound BIP-BNO

We have measured the magnetization of the organic compound BIP-BNO (3,5'-bis(N-tert-butylaminoxyl)-3',5-dibromobiphenyl) up to 76 T where the magnetization is saturated. The S = 1/2 antiferromagnetic Heisenberg two-leg spin-ladder model accounts for the obtained experimental data regarding the magnetization curve, which is clarified using the quantum Monte Carlo method. The exchange constants on the rung and the side rail of the ladder are estimated to be J(rung)/kB = 65.7 K and J(leg)/kB = 14.1 K, respectively, deeply in the strong coupling region: J(rung)/J(leg) > 1.

cond-mat.str-el↗

arXiv2017

High-speed 100 MHz strain monitor using fiber Bragg grating and optical filter for magnetostriction measurements under ultrahigh magnetic fields

A high-speed 100 MHz strain monitor using a fiber Bragg grating, an optical filter, and a mode-locked optical fiber laser has been devised, which has a resolution of $ΔL/L\sim10^{-4}$. The strain monitor is sufficiently fast and robust for the magnetostriction measurements of magnetic materials under ultrahigh magnetic fields generated with destructive pulse magnets, where the sweep rate is in the range of 10-100 T/$μ$s. As a working example, the magnetostriction of LaCoO$_{3}$ was measured at room temperature, 115 K, and 7$\sim$4.2 K up to a maximum magnetic field of 150 T. The smooth $B^{2}$ dependence and the first-order transition were observed at 115 K and 7$\sim$4.2 K, respectively, reflecting the field-induced spin-state evolution.

cond-mat.mtrl-sci↗

arXiv2017

$H$-$T$ phase diagram of solid oxygen

Comprehensive magnetic-field-temperature ($H$-$T$) phase diagram of solid oxygen including the $θ$ phase is discussed in the context of the ultrahigh-field measurement and the magnetocaloric effect (MCE) measurement. The problems originating from the short duration of the pulse field, non-equilibrium condition and MCEs, are pointed out and dealt with. The obtained phase diagram manifests the entropy relation between the phases as $S_θ\sim S_α<S_β<<S_γ$.

cond-mat.mtrl-sci↗

arXiv2017

$α$-$β$ and $β$-$γ$ phase boundaries of solid oxygen observed by adiabatic magnetocaloric effect

The magnetic-field-temperature phase diagram of solid oxygen is investigated by the adiabatic magnetocaloric effect (MCE) measurement with pulsed magnetic fields. Relatively large temperature decrease with hysteresis is observed at just below the $β$-$γ$ and $α$-$β$ phase transition temperatures owing to the field-induced transitions. The magnetic field dependences of these phase boundaries are obtained as $T_\mathrm{βγ}(H)=43.8-1.55\times10^{-3}H^2$ K and $T_\mathrm{αβ}(H)=23.9-0.73\times10^{-3}H^2$ K. The magnetic Clausius-Clapeyron equation quantitatively explains the $H$ dependence of $T_\mathrm{βγ}$, meanwhile, does not $T_\mathrm{αβ}$. The MCE curve at $T_\mathrm{βγ}$ is of typical first-order, while the curve at $T_\mathrm{αβ}$ seems to have both characteristics of first- and second-order transitions. We discuss the order of the $α$-$β$ phase transition and propose possible reasons for the unusual behavior.

cond-mat.mtrl-sci↗