arXiv subjects

Y. Matsuda

Publications and source records attributed to Y. Matsuda.

At least 73 records · Page 4Linked to original sources

arXiv2021

Sympathetic cooling of a trapped proton mediated by an LC circuit

Efficient cooling of trapped charged particles is essential to many fundamental physics experiments, to high-precision metrology, and to quantum technology. Until now, sympathetic cooling has required close-range Coulomb interactions, but there has been a sustained desire to bring laser-cooling techniques to particles in macroscopically separated traps, extending quantum control techniques to previously inaccessible particles such as highly charged ions, molecular ions and antimatter. Here we demonstrate sympathetic cooling of a single proton using laser-cooled Be+ ions in spatially separated Penning traps. The traps are connected by a superconducting LC circuit that enables energy exchange over a distance of 9 cm. We also demonstrate the cooling of a resonant mode of a macroscopic LC circuit with laser-cooled ions and sympathetic cooling of an individually trapped proton, reaching temperatures far below the environmental temperature. Notably, as this technique uses only image-current interactions, it can be easily applied to an experiment with antiprotons, facilitating improved precision in matter-antimatter comparisons and dark matter searches.

physics.atom-ph↗

arXiv2021

Pressure-induced reconstitution of Fermi surfaces and spin fluctuations in S-substituted FeSe

FeSe is a unique high-$T_c$ iron-based superconductor in which nematicity, superconductivity, and magnetism are entangled with each other in the $P$-$T$ phase diagram. We performed $^{77}$Se-nuclear magnetic resonance measurements under pressures of up to 3.9 GPa on 12% S-substituted FeSe, in which the complex overlap between the nematicity and magnetism are resolved. A pressure-induced Lifshitz transition was observed at 1.0 GPa as an anomaly of the density of states and as double superconducting (SC) domes accompanied by different types of antiferromagnetic (AF) fluctuations. The low-$T_{\rm c}$ SC dome below 1 GPa is accompanied by strong AF fluctuations, whereas the high-$T_{\rm c}$ SC dome develops above 1 GPa, where AF fluctuations are fairly weak. These results suggest the importance of the $d_{xy}$ orbital and its intra-orbital coupling for the high-$T_{\rm c}$ superconductivity.

cond-mat.supr-con↗

arXiv2021

Topological surface conduction in Kondo insulator YbB$_{12}$

Kondo insulators have recently aroused great interest because they are promising materials that host a topological insulator state caused by the strong electron interactions. Moreover, recent observations of the quantum oscillations in the insulating state of Kondo insulators have come as a great surprise. Here, to investigate the surface electronic state of a prototype Kondo insulator YbB$_{12}$, we measured transport properties of single crystals and microstructures. In all samples, the temperature dependence of the electrical resistivity is insulating at high temperatures and the resistivity exhibits a plateau at low temperatures. The magnitude of the plateau value decreases with reducing sample thickness, which is quantitatively consistent with the surface electronic conduction in the bulk insulating YbB$_{12}$. Moreover, the magnetoresistance of the microstructures exhibits a weak-antilocalization effect at low field. These results are consistent with the presence of topologically protected surface state, suggesting that YbB$_{12}$ is a candidate material of the topological Kondo insulator. The high field resistivity measurements up to $μ_0H$ = 50 T of the microstructures provide supporting evidence that the quantum oscillations of the resistivity in YbB$_{12}$ occurs in the insulating bulk.

cond-mat.str-el↗

arXiv2021

Universal scaling of the specific heat in $S=1/2$ quantum kagome antiferromagnet herbertsmithite

Despite tremendous investigations, a quantum spin liquid state realized in spin-1/2 kagome Heisenberg antiferromagnet remains largely elusive. In herbertsmithite ZnCu$_3$(OH)$_6$Cl$_2$, a quantum spin liquid candidate on the perfect kagome lattice, precisely characterizing the intrinsic physics of the kagome layers is extremely challenging due to the presence of interlayer Cu/Zn antisite disorder within its crystal structure. Here we measured the specific heat and thermal conductivity of single crystal herbertsmithite in magnetic fields with high resolution. Our results are highlighted by the excellent scaling collapse of the intrinsic magnetic specific heat contribution arising from the kagome layers as a function of $T/H$ (temperature/magnetic field). In addition, no residual linear term in the thermal conductivity $κ/T(T\rightarrow 0)$ is observed in zero and applied magnetic fields, indicating the absence of itinerant gapless excitations. These results suggest a new picture for a quantum spin liquid state of the kagome layers of herbertsmithite, wherein localized orphan spins arise and interact with random exchanges in conjunction with a non-itinerant quantum spin liquid.

cond-mat.str-el↗

arXiv2021

Quadrupolar charge dynamics in the nonmagnetic FeSe$_{1-x}$S$_x$ superconductors

We use polarization-resolved electronic Raman spectroscopy to study charge dynamics in non-magnetic FeSe$_{1-x}$S$_x$ superconductor. We observe two features of the $XY$ quadrupole symmetry: a low-energy quasi-elastic peak (QEP) and an electronic continuum. The QEP exhibits critical enhancement upon cooling towards the structural transition at $T_S(x)$. Below $T_S(x)$, the QEP diminishes gradually, and a gap with temperature evolution reminiscent of a mean-field order parameter opens in the continuum. The intensity of the QEP develops with increasing sulfur doping $x$ and maximizes at $x\approx$ 0.15, while the gap magnitude decreases with the suppression of $T_S(x)$. We interpret the development of the gap in the quadrupole scattering channel as the formation of a stripe quadrupole order: a wave of quadrupole moment without charge or spin modulation.

cond-mat.supr-con↗

arXiv2021

Physical Characterization of Serendipitously Uncovered Millimeter-wave Line-emitting Galaxies at z~2.5 behind the Local Luminous Infrared Galaxy VV114

We present a detailed investigation of millimeter-wave line emitters ALMA J010748.3-173028 (ALMA-J0107a) and ALMA J010747.0-173010 (ALMA-J0107b), which were serendipitously uncovered in the background of the nearby galaxy VV114 with spectral scan observations at $λ$ = 2 - 3 mm. Via Atacama Large Millimeter/submillimeter Array (ALMA) detection of CO(4-3), CO(3-2), and [CI](1-0) lines for both sources, their spectroscopic redshifts are unambiguously determined to be $z= 2.4666\pm0.0002$ and $z=2.3100\pm0.0002$, respectively. We obtain the apparent molecular gas masses $M_{\rm gas}$ of these two line emitters from [CI] line fluxes as $(11.2 \pm 3.1) \times 10^{10} M_\odot$ and $(4.2 \pm 1.2) \times 10^{10} M_\odot$, respectively. The observed CO(4-3) velocity field of ALMA-J0107a exhibits a clear velocity gradient across the CO disk, and we find that ALMA-J0107a is characterized by an inclined rotating disk with a significant turbulence, that is, a deprojected maximum rotation velocity to velocity dispersion ratio $v_{\rm max}/σ_{v}$ of $1.3 \pm 0.3$. We find that the dynamical mass of ALMA-J0107a within the CO-emitting disk computed from the derived kinetic parameters, $(1.1 \pm 0.2) \times 10^{10}\ M_\odot$, is an order of magnitude smaller than the molecular gas mass derived from dust continuum emission, $(3.2\pm1.6)\times10^{11}\ M_{\odot}$. We suggest this source is magnified by a gravitational lens with a magnification of $μ\gtrsim10$, which is consistent with the measured offset from the empirical correlation between CO-line luminosity and width.

astro-ph.GA↗

arXiv2021

Candidates for the 5$α$ condensed state in ${}^{20}$Ne

We conducted the coincidence measurement of $α$ particles inelastically scattered from ${}^{20}$Ne at $0^{\circ}$ and decay charged particles in order to search for the alpha-particle condensed state. We compared the measured excitation-energy spectrum and decay branching ratio with the statistical-decay-model calculations, and found that the newly observed states at $E_x$ = 23.6, 21.8, and 21.2 MeV in ${}^{20}$Ne are strongly coupled to a candidate for the 4$α$ condensed state in ${}^{16}$O. This result presents the first strong evidence that these states are the candidates for the 5$α$ condensed state.

nucl-ex↗

arXiv2021

Thermodynamics of transition to BCS-BEC crossover superconductivity in FeSe$_{1-x}$S$_x$

The BCS-BEC crossover from strongly overlapping Cooper pairs to non-overlapping composite bosons in the strong coupling limit has been a long-standing issue of interacting many-body fermion systems. Recently, FeSe semimetal with hole and electron bands emerged as a high-$T_{\rm c}$ superconductor located in the BCS-BEC crossover regime, owing to its very small Fermi energies. In FeSe, however, an ordinary BCS-like heat-capacity jump is observed at $T_{\rm c}$, posing a fundamental question on the characteristics of the BCS-BEC crossover. Here we report on high-resolution heat capacity, magnetic torque, and scanning tunneling spectroscopy measurements in FeSe$_{1-x}$S$_x$. Upon entering the tetragonal phase at $x>0.17$, where nematic order is suppressed, $T_{\rm c}$ discontinuously decreases. In this phase, highly non-mean-field behaviors consistent with BEC-like pairing are found in the thermodynamic quantities with giant superconducting fluctuations extending far above $T_{\rm c}$, implying the change of pairing nature. Moreover, the pseudogap formation, which is expected in BCS-BEC crossover of single-band superconductors, is not observed in the tunneling spectra. These results illuminate highly unusual features of the superconducting states in the crossover regime with multiband electronic structure and competing electronic instabilities.

cond-mat.supr-con↗

arXiv2021

Charge neutral fermions and magnetic field driven instability in insulating YbIr$_3$Si$_7$

Materials where localized magnetic moments are coupled to itinerant electrons, the so-called Kondo lattice materials, provide a very rich backdrop for strong electron correlations. They are known to realize many exotic phenomena, including unconventional superconductivity, strange metals, and correlated topological phases of matter. Here, we report what appears to be electron fractionalization in insulating Kondo lattice material YbIr$_3$Si$_7$, with emergent neutral excitations that carry heat but not electric current and contribute to metal-like specific heat. We show that these neutral particles change their properties as the material undergoes a transformation between two antiferromagnetic phases in an applied magnetic field. In the low-field AF-I phase, we find that the low temperature linear specific heat coefficient $γ$ and the residual linear term in the thermal conductivity $κ/T(T\rightarrow 0)$ are finite, demonstrating itinerant gapless excitations. These results, along with a spectacular violation of the Wiedemann-Franz law, directly indicate that YbIr$_3$Si$_7$ is a charge insulator but a thermal metal. Nuclear magnetic resonance spectrum reveals a spin-flop transition to a high field AF-II phase. Near the transition field, $γ$ is significantly enhanced. Most surprisingly, inside the AF-II phase, $κ/T$ exhibits a sharp drop below $\sim300$ mK, indicating either opening of a tiny gap or a linearly vanishing density of states. This finding demonstrates a transition from a thermal metal into an insulator/semimetal driven by the spin-flop magnetic transition. These results suggest that spin degrees of freedom directly couple to the neutral fermions, whose emergent Fermi surface undergoes a field-driven instability at low temperatures.

cond-mat.str-el↗

arXiv2021

New precise spectroscopy of the hyperfine structure in muonium with a high-intensity pulsed muon beam

A hydrogen-like atom consisting of a positive muon and an electron is known as muonium. It is a near-ideal two-body system for a precision test of bound-state theory and fundamental symmetries. The MuSEUM collaboration performed a new precision measurement of the muonium ground-state hyperfine structure at J-PARC using a high-intensity pulsed muon beam and a high-rate capable positron counter. The resonance of hyperfine transition was successfully observed at a near-zero magnetic field, and the muonium hyperfine structure interval of $ν_{\text{HFS}}$ = 4.463302(4) GHz was obtained with a relative precision of 0.9 ppm. The result was consistent with the previous ones obtained at Los Alamos National Laboratory and the current theoretical calculation. We present a demonstration of the microwave spectroscopy of muonium for future experiments to achieve the highest precision.

hep-ex↗

arXiv2021

Rabi-Oscillation Spectroscopy of the Hyperfine Structure of Muonium Atoms

As a new method to determine the resonance frequency, Rabi-oscillation spectroscopy has been developed. In contrast to the conventional spectroscopy which draws the resonance curve, Rabi-oscillation spectroscopy fits the time evolution of the Rabi oscillation. By selecting the optimized frequency, it is shown that the precision is twice as good as the conventional spectroscopy with a frequency sweep. Furthermore, the data under different conditions can be treated in a unified manner, allowing more efficient measurements for systems consisting of a limited number of short-lived particles produced by accelerators such as muons. We have developed a fitting function that takes into account the spatial distribution of muonium and the spatial distribution of the microwave intensity to apply the new method to ground-state muonium hyperfine structure measurements at zero field. This was applied to the actual measurement data and the resonance frequencies were determined under various conditions. The result of our analysis gives $ν_{\rm HFS}=4\ 463\ 301.61 \pm 0.71\ {\rm kHz}$, which is the world's highest precision under zero field conditions.

hep-ex↗

arXiv2020

Measurement of the Principal Quantum Number Distribution in a Beam of Antihydrogen Atoms

The ASACUSA (Atomic Spectroscopy And Collisions Using Slow Antiprotons) collaboration plans to measure the ground-state hyperfine splitting of antihydrogen in a beam at the CERN Antiproton Decelerator with initial relative precision of 10-6 or better, to test the fundamental CPT (combination of charge conjugation, parity transformation and time reversal) symmetry between matter and antimatter. This challenging goal requires a polarised antihydrogen beam with a sufficient number of antihydrogen atoms in the ground state. The first measurement of the quantum state distribution of antihydrogen atoms in a low magnetic field environment of a few mT is described. Furthermore, the data-driven machine learning analysis to identify antihydrogen events is discussed.

physics.atom-ph↗

arXiv2020

Timeliness-aware On-site Planning Method for Tour Navigation

In recent years, there has been a growing interest in travel applications that provide on-site personalized tourist spot recommendations. While generally helpful, most available options offer choices based solely on static information on places of interest without consideration of such dynamic factors as weather, time of day, and congestion, and with a focus on helping the tourist decide what single spot to visit next. Such limitations may prevent visitors from optimizing the use of their limited resources (i.e., time and money). Some existing studies allow users to calculate a semi-optimal tour visiting multiple spots in advance, but their on-site use is difficult due to the large computation time, no consideration of dynamic factors, etc. To deal with this situation, we formulate a tour score approach with three components: static tourist information on the next spot to visit, dynamic tourist information on the next spot to visit, and an aggregate measure of satisfaction associated with visiting the next spot and the set of subsequent spots to be visited. Determining the tour route that produces the best overall tour score is an NP-hard problem for which we propose three algorithms on the greedy method. To validate the usefulness of the proposed approach, we applied the three algorithms to 20 points of interest in Higashiyama, Kyoto, Japan, and confirmed that the output solution was superior to the model route for Kyoto, with computation times of the three algorithms of $1.9\pm0.1$, $2.0\pm0.1$, and $27.0\pm1.8$ s.

cs.DS↗

arXiv2020

An ALMA/NOEMA survey of the molecular gas properties of high-redshift star-forming galaxies

We present a survey of the molecular gas in 61 submillimetre galaxies (SMGs) selected from 870$μ$m continuum surveys of the COSMOS, UDS and ECDFS fields, using the Atacama Large Millimeter Array (ALMA) and the Northern Extended Millimeter Array (NOEMA). 46 $^{12}$CO ($J=$2-5) emission lines are detected in 45 of the targets at $z=$1.2-4.8, with redshifts indicating that those which are submillimetre bright and undetected/faint in the optical/near-infrared typically lie at higher redshifts, with a gradient of $Δz/ΔS_{870}=$0.11$\pm$0.04mJy$^{-1}$. We also supplement our data with literature sources to construct a statistical CO spectral line energy distribution and find the $^{12}$CO line luminosities in SMGs peak at $J_{\rm up}\sim$6, consistent with the Cosmic Eyelash, among similar studies. Our SMGs lie mostly on or just above the main sequence, displaying a decrease in their gas depletion timescales $t_{\rm dep} = M_{\rm gas}/{\rm SFR}$ with redshift in the range $z\sim$1-5 and a median of 200$\pm$50Myr at $z\sim$2.8. This coincides with an increase in molecular gas fraction $μ_{\rm gas} = M_{\rm gas}/M_\ast$ across the same redshift range. Finally we demonstrate that the $M_{\rm baryon}$-$σ$ distribution of our SMGs is consistent with that followed by early-type galaxies in the Coma cluster, providing strong support to the suggestion that SMGs are progenitors of massive local spheroidal galaxies. On the basis of this we suggest that the SMG populations above and below an 870-$μ$m flux limit of $S_{870}\sim$5mJy may correspond to the division between slow- and fast-rotators seen in local early-type galaxies.

astro-ph.GA↗

arXiv2020

Non-Fermi liquid transport in the vicinity of nematic quantum critical point of FeSe$_{1-x}$S$_x$ superconductor

Non-Fermi liquids are strange metals whose physical properties deviate qualitatively from those of conventional metals due to strong quantum fluctuations. In this paper, we report transport measurements on the FeSe$_{1-x}$S$_x$ superconductor, which has a quantum critical point of a nematic order without accompanying antiferromagnetism. We find that in addition to a linear-in-temperature resistivity $ρ_{xx}\propto T$, which is close to the Planckian limit, the Hall angle varies as $\cot θ_{\rm H} \propto T^2$ and the low-field magnetoresistance is well scaled as $Δρ_{xx}/ρ_{xx}\propto \tan^2 θ_{\rm H}$ in the vicinity of the nematic quantum critical point. This set of anomalous charge transport properties shows striking resemblance with those reported in cuprate, iron-pnictide and heavy fermion superconductors, demonstrating that the critical fluctuations of a nematic order with ${\bf q} \approx 0$ can also lead to a breakdown of the Fermi liquid description.

cond-mat.supr-con↗

arXiv2020

Bond Directional Anapole Order in a Spin-Orbit Coupled Mott Insulator Sr$_2$(Ir$_{1-x}$Rh$_x$)O$_{4}$

An anapole state that breaks inversion and time reversal symmetries with preserving translation symmetry of underlying lattice has aroused great interest as a new quantum state, but only a few candidate materials have been reported. Recently, in a spin-orbit coupled Mott insulator \SIR, the emergence of a possible hidden order phase with broken inversion symmetry has been suggested at $T_Ω$ above the Néel temperature by optical second harmonic generation measurements. Moreover, polarized neutron diffraction measurements revealed the broken time reversal symmetry below $T_Ω$, which was supported by subsequent muon spin relaxation experiments. However, the nature of this mysterious phase remains largely elusive. Here, we investigate the hidden order phase through the combined measurements of the in-plane magnetic anisotropy with exceptionally high-precision magnetic torque and the nematic susceptibility with elastoresistance. A distinct two-fold in-plane magnetic anisotropy along the [110] Ir-O-Ir bond direction sets in below $\sim T_Ω$, providing thermodynamic evidence for a nematic phase transition with broken $C_4$ rotational symmetry. However, in contrast to the even-parity nematic transition reported in other correlated electron systems, the nematic susceptibility exhibits no divergent behavior towards $T_Ω$. These results provide bulk evidence for an odd-parity order parameter with broken rotational symmetry in the hidden order state. We discuss the hidden order in terms of an anapole state, in which polar toroidal moment is induced by two current loops in each IrO$_6$ octahedron of opposite chirality. Contrary to the simplest loop-current pattern previously suggested, the present results are consistent with a pattern in which the intra-unit cell loop-current flows along only one of the diagonal directions in the IrO$_4$ square.

cond-mat.str-el↗

arXiv2020

Compressional-mode resonances in the molybdenum isotopes: Emergence of softness in open-shell nuclei near A=90

"Why are the tin isotopes soft?" has remained, for the past decade, an open problem in nuclear structure physics: models which reproduce the isoscalar giant monopole resonance (ISGMR) in the "doubly-closed shell" nuclei, $^{90}$Zr and $^{208}$Pb, overestimate the ISGMR energies of the open-shell tin and cadmium nuclei, by as much as 1 MeV. In an effort to shed some light onto this problem, we present results of detailed studies of the ISGMR in the molybdenum nuclei, with the goal of elucidating where--and how--the softness manifests itself between $^{90}$Zr and the cadmium and tin isotopes. The experiment was conducted using the $^{94,96,98,100}$Mo($α,α^\prime$) reaction at $E_α= 386$ MeV. A comparison of the results with relativistic, self-consistent Random-Phase Approximation calculations indicates that the ISGMR response begins to show softness in the molybdenum isotopes beginning with $A=92$.

nucl-ex↗

arXiv2020

Observation of a $\bar{K}NN$ bound state in the $^3{\rm He} (K^-, Λp)n$ reaction

We have performed an exclusive measurement of the $K^{-}+\! ~^{3}{\rm He} \to Λpn$ reaction at an incident kaon momentum of $1\ {\rm GeV}/c$.In the $Λp$ invariant mass spectrum, a clear peak was observed below the mass threshold of $\bar{K}\!+\!N\!+\!N$, as a signal of the kaonic nuclear bound state, $\bar{K}NN$.The binding energy, decay width, and $S$-wave Gaussian reaction form-factor of this state were observed to be $B_{K} = 42\pm3({\rm stat.})^{+3}_{-4}({\rm syst.})\ {\rm MeV}$, $Γ_{K} = 100\pm7({\rm stat.})^{+19}_{-9}({\rm syst.})\ {\rm MeV}$, and $Q_{K} = 383\pm11({\rm stat.})^{+4}_{-1}({\rm syst.})\ {\rm MeV}/c$, respectively. The total production cross-section of $\bar{K}NN$, determined by its $Λp$ decay mode, was $σ^{tot}_{K} \cdot BR_{Λp} = 9.3\pm0.8({\rm stat.})^{+1.4}_{-1.0}({\rm syst.})\ μ{\rm b}$.We estimated the branching ratio of the $\bar{K}NN$ state to the $Λp$ and $Σ^{0}p$ decay modes as $BR_{Λp}/BR_{Σ^{0}p} \sim 1.7$, by assuming that the physical processes leading to the $ΣN\!N$ final states are analogous to those of $Λpn$.

nucl-ex↗