arXiv subjects

Toshiro Takabatake

Publications and source records attributed to Toshiro Takabatake.

At least 19 recordsLinked to original sources

arXiv2026

Magnetic field and pressure tuning of the heavy fermion antiferromagnet CePdIn

Frustrated Kondo lattices are ideal platforms for studying how both the Kondo effect and quantum fluctuations compete with the magnetic exchange interactions that drive magnetic ordering. Here, we investigate the effect of tuning the heavy-fermion compound CePdIn, which crystallizes in the geometrically frustrated ZrNiAl-type structure, using applied magnetic fields and hydrostatic pressure. At ambient pressure, CePdIn exhibits two magnetic transitions, one at $T_{\rm{N}} \approx 1.65$ K and another at $T_{\rm{M}} \approx 1.15$ K, which are both suppressed by applied $c$-axis fields. Upon applying pressure in zero magnetic field, there is a non-monotonic evolution of $T_{\rm{N}}$, which decreases to 0.8 K at 2.3 GPa, before abruptly increasing to 1.5 K at 2.6 GPa. At higher pressures, $T_{\rm{N}}$ has a weak pressure dependence, and vanishes near 5 GPa. Together with the high-pressure phase being more robust to applied fields, these results suggest two distinct antiferromagnetic phases in CePdIn, which are separated near 2.6 GPa, and this change may be driven by the evolution of the underlying electronic structure due to enhanced Kondo hybridization under pressure.

cond-mat.str-el↗

arXiv2026

Coherent magnetic excitations in a topological Kondo semimetal

In Kondo insulators the many-body Kondo lattice effect drives the formation of bands containing heavy charge carriers with a hybridization gap, leading to insulating properties. These renormalized bands can host non-trivial topologies driven by strong electron-electron interactions, but probing narrow heavy bands at low temperatures is challenging. We use inelastic neutron scattering (INS) to probe the Kondo lattice CeNiSn, which hosts both semimetallic transport properties and a hybridization gap. The INS response exhibits momentum-dependent magnetic excitations and a spin-gap in the low-temperature Kondo coherent state, which electronic structure calculations corroborate as arising from the renormalized heavy band structure. Dynamical-mean field theory demonstrates that this renormalized band structure corresponds to a topological Kondo insulating state, and hence the INS probes bulk excitations of heavy topological bands. This identification of a Kondo insulator addresses the long-standing mystery of the electronic properties of CeNiSn, and demonstrates the manifestation of a topological many-body coherent state in spectroscopic measurements of strongly correlated narrow band materials.

cond-mat.str-el↗

arXiv2025

Quantum Griffiths phase in the kagome Kondo lattice CeRh$_{0.9}$Pd$_{0.1}$Sn

CeRhSn is a valence fluctuating heavy-fermion metal with a twisted Ce-kagome lattice, displaying zero-field quantum criticality, previously associated with geometrical frustration. The partial substitution of Rh by Pd in CeRh$_{1-x}$Pd$_x$Sn enlarges the unit-cell volume, suppresses valence fluctuations, decreases the Kondo temperature and stabilizes a possible long-range antiferromagnetic (AFM) ordered ground state with $T_N=0.8$ K at $x=0.5$. Previous thermodynamic and spectroscopic measurements for $x=0.1$ suggested a quantum critical spin liquid. We report low-temperature dilatometry and magnetization measurements on CeRh$_{0.9}$Pd$_{0.1}$Sn and compare with published low-$T$ specific heat data. The absence of a Grüneisen parameter divergence excludes a conventional quantum criticality scenario. Instead, the weak power-law divergences signal non-Fermi liquid (NFL) behavior, according to a disorder-driven quantum Griffiths phase scenario. At low temperatures, a negative thermal expansion is found in fields above approximately 0.5 T and the NFL scaling breaks down, probably due to the polarization of AFM correlations.

cond-mat.str-el↗

arXiv2025

Anisotropic Non-Fermi Liquid and Dynamical Planckian Scaling of a Quasi-Kagome Kondo Lattice System

At the quantum critical point of correlated materials, a non-Fermi liquid state appears where electron correlations continuously develop to very low temperatures. The relaxation time of the interacted electrons, namely quasiparticles, is scaled with the Planckian time, $\hbar/k_{\rm B}T$. However, there is a debate over whether heavy-fermion systems can obey the Planckian time. In the optical conductivity spectra, the Drude response will appear as the scaling of $\hbarω/k_{\rm B}T$ as the dynamical Planckian scaling (DPS). Here, we report the non-Fermi liquid behavior in the Drude response of a candidate for such materials, the quasi-kagome Kondo lattice CeRhSn. Even though the material shows a strong valence fluctuation, renormalized Drude responses observed at the photon energy below 100 meV are characterized by non-Fermi-liquid-like scattering rate $1/τ$. The heavy carriers' Drude response only for the Ce quasi-kagome plane obeyed DPS below 80 K, suggesting the anisotropic quantum criticality with the strong $c \textrm{-} f$ hybridization.

cond-mat.str-el↗

arXiv2025

Antiferromagnetic Order and Magnetic Frustration in the Honeycomb Heavy-Fermion System Ce(Pt$_{1-x}$Pd$_{x}$)$_6$Al$_3$: $^{27}$Al and $^{195}$Pt NMR Studies

Heavy-fermion systems with magnetic frustration offer a rich platform for investigating the interplay among Kondo screening, magnetic frustration, and quantum criticality. We report comprehensive $^{27}$Al and $^{195}$Pt nuclear magnetic resonance measurements on polycrystalline Ce(Pt$_{1-x}$Pd$_{x}$)$_6$Al$_3$ ($x = 0$, 0.1, 0.2, and 0.3). For $x = 0$, the Knight shift, linewidth, and nuclear spin-lattice relaxation rate reveal a paramagnetic heavy-fermion ground state persisting down to 0.1~K, characterized by a coherence temperature $T_{\mathrm{coh}} \simeq 15$~K. Substituting Pd induces antiferromagnetic order at $T_{\mathrm{N}} \simeq 3.5$~K, while suppressing $T_{\mathrm{coh}}$. Comparison between $x = 0.1$ and $x = 0.3$ reveals a crossover from itinerant spin-density-wave antiferromagnetism to more localized-moment antiferromagnetism, indicating a shift toward the localized side of the Doniach phase diagram. These findings establish Ce(Pt$_{1-x}$Pd$_{x}$)$_6$Al$_3$ as a tunable platform to explore the competition between Kondo screening and magnetic frustration.

cond-mat.str-el↗

arXiv2025

Multipolar Phase Transition in the 4$f^2$ fcc lattice compound PrCdNi$_{4}$

Transport and magnetic properties of a 4$f^{2}$ fcc lattice compound, PrCdNi$_4$, were studied. The magnetic susceptibility, $χ(T)$, follows the Curie--Weiss law from 300 K to 20 K, as expected for a free Pr$^{3+}$ ion. As the temperature decreases below 5 K, $χ(T)$ approaches a constant, indicating van-Vleck paramagnetic behavior. The specific heat, $C(T)$, displays a broad shoulder at around 4 K, which can be reproduced by a doublet triplet two-level model with an energy gap of 12 K. These results suggest a non-magnetic $Γ_3$ doublet ground state of the Pr$^{3+}$ ion in the cubic crystalline electric field. $C(T)$ exhibits a peak at $T_{\rm O}$ = 1.0 K and this peak remains robust against magnetic fields up to 5 T. In powder neutron diffraction measurements, no magnetic reflection was observed at 0.32 K $<$ $T_{\rm O}$. Two anomalies at $B$ = 2.1 and 5.3 T in magnetoresistance $ρ(B)$ at 0.05 K likely originate from switching in the order parameter. These results suggest that the phase transition at $T_{\rm O}$ is ascribed to an antiferro-type order of the electric quadrupole or magnetic octupole of the $Γ_3$ doublet in the 4$f^2$ fcc lattice.

cond-mat.str-el↗

arXiv2025

Single-site quadrupolar Kondo effect in a diluted non-Kramers doublet system Y$_{1-x}$Pr$_x$Ir$_2$Zn$_{20}$ for $x = 0.028$ viewed from magnetization

A diluted non-Kramers doublet system Y$_{1-x}$Pr$_x$Ir$_2$Zn$_{20}$ is a promising candidate for exhibiting single-site quadrupolar (two-channel) Kondo effect. We have measured temperature-dependent magnetization of a sample for $x$ = 0.028 down to 0.1 K at various constant magnetic fields to extract the characteristic behaviors due to the quadrupolar Kondo effect. The Curie--Weiss fit to the magnetic susceptibility between 50 and 300 K yields a negative paramagnetic Curie temperature of $-$7.0 K, indicative of on-site antiferromagnetic interaction. The magnetization divided by magnetic field, $M(T)/B$, at $B = 0.5$ T is saturated to a constant value below 3 K. On the contrary, in higher magnetic fields of $B$ = 1 and 2 T, $M(T)/B$ exhibits $-$ln$T$ dependence from 1 to 0.1 K, which temperature dependence is consistent with that of the quadrupolar susceptibility detected from ultrasonic measurements. The $-$ln$T$ form of $M(T)/B$ appears to reflect the behavior of quadrupolar susceptibility, through the magnetic-field-induced magnetic moment due to the mixing of the non-Kramers doublet and crystalline-electric-field excited states of Pr$^{3+}$. In $B$ = 4 T, $M(T)/B$ approaches a constant on cooling below 0.3 K, because of the quenching of the quadrupoles in the field-induced singlet ground state.

cond-mat.str-el↗

arXiv2025

Rotational Grüneisen ratio: a probe for quantum criticality in anisotropic systems

The Grüneisen ratio $Γ$ and its magnetic analog, the magnetic Grüneisen ratio $Γ_H$, are powerful probes to study the nature of quantum phase transitions. Here, we propose a Grüneisen parameter, the rotational Grüneisen ratio $Γ_ϕ$, by introducing the orientation of the external field as a control parameter. We investigate $Γ_ϕ$ of the highly anisotropic paramagnets CeRhSn and CeIrSn by measuring the rotational magnetocaloric effect in a wide range of temperatures and magnetic fields. We find that the $Γ_ϕ$ data of both compounds are scaled by using the same critical exponents and the field-invariant critical field angle. Remarkably, the scaling function for the $Γ_ϕ$ data reveals the presence of highly anisotropic quantum criticality that develops as a function of the easy-axis component of the magnetic field from the quantum critical line. This paper provides a thermodynamic approach to detect and identify magnetic quantum criticality in highly anisotropic systems.

cond-mat.str-el↗

arXiv2024

Structural Evolution from Hyper-Honeycomb to Honeycomb Networks and Superconductivity in LaPt$_x$Si$_{2-x}$

We report the crystal structures and superconductivity (SC) of LaPt$_{x}$Si$_{2-x}$ ($0.5 \leq x \leq 1.0$) that are solid solutions of LaSi$_{2}$ and LaPtSi with centrosymmetric tetragonal ($I4_{1}/amd$, $D_{4h}^{19}$, \#141) and non-centrosymmetric tetragonal ($I4_{1}md$, $C_{4v}^{11}$, \#109) structures, respectively. It was found that at $0.86 \leq x \leq 1.00$, the non-centrosymmetric tetragonal symmetry is preserved, while partial disorder appears in alternating Pt and Si of the hyper-honeycomb network. The superconducting transition temperature $T_{\rm c}$ was drastically reduced from 3.9 K to 1.5 K as $x$ varies from 1.0 to 0.86. Additionally, a hexagonal phase with an AlB$_{2}$-type structure ($P6/mmm$, $D_{6h}^{1}$, \#191) has been discovered at $0.50 \leq x \leq 0.71$ with a honeycomb network of statistically distributed Pt and Si atoms. The hexagonal phase exhibited SC at $T_{\rm c} = 0.38$ K. This system provides an opportunity to investigate the relationship between topological electronic states, SC, and disorders

cond-mat.supr-con↗

arXiv2023

Inelastic neutron scattering study of crystalline electric field excitations in the caged compounds NdT2Zn20 (T = Co, Rh, and Ir)

We have measured crystalline electric field (CEF) excitations of Nd3+ ions in the two-channel Kondo lattice candidates NdT2Zn20 (T = Co, Rh, and Ir) by means of inelastic neutron scattering (INS). In the INS measurements at 5 K, dispersionless excitations were observed at 3.8 and 7.2 meV for T = Co, 3.1 and 5.8 meV for T = Rh, and 3.0 and 5.3 meV for T = Ir. Analyses of the temperature dependence of the INS spectra confirm that the CEF ground states are the Gamma 6 doublet, that is a requisite for manifestation of the magnetic two-channel Kondo effect. For T = Co, a shoulder was observed at 7.7 meV close to the CEF excitation peak centered at 7.2 meV. The shoulder is attributed to a bound state of the CEF and low-lying optical phonon excitations.

cond-mat.str-el↗

arXiv2022

A Family of Lanthanide Noncentrosymmetric Superconductors La$_4$$TX$ ($T$ = Ru, Rh, Ir; $X$ = Al, In)

We report the discovery of superconductivity in a series of noncentrosymmetric compounds La$_4$$TX$ ($T$ = Ru, Rh, Ir; $X$ = Al, In), which have a cubic crystal structure with space group $F\bar{4}3m$. La$_4$RuAl, La$_4$RhAl, La$_4$IrAl, La$_4$RuIn and La$_4$IrIn exhibit bulk superconducting transitions with critical temperatures $T_c$ of 1.77 K, 3.05 K, 1.54 K, 0.58 K and 0.93 K, respectively. The specific heat of the La$_4$$T$Al compounds are consistent with an $s$-wave model with a fully open superconducting gap. In all cases, the upper critical fields are well described by the Werthamer-Helfand-Hohenberg model, and the values are well below the Pauli limit, indicating that orbital limiting is the dominant pair-breaking mechanism. Density functional theory (DFT) calculations reveal that the degree of band splitting by the antisymmetric spin-orbit coupling (ASOC) shows considerable variation between the different compounds. This indicates that the strength of the ASOC is highly tunable across this series of superconductors, suggesting that these are good candidates for examining the relationship between the ASOC and superconducting properties in noncentrosymmetric superconductors.

cond-mat.supr-con↗

arXiv2022

Quantitative investigation of the 4$f$ occupation in the quasikagome Kondo lattice CeRh$_{1-x}$Pd$_x$Sn

CeRhSn with the Ce atoms forming a quasikagome lattice in the hexagonal plane has recently been discussed in the context of quantum criticality driven by magnetic frustration. Furthermore, it has been reported that the successive substitution of Rh by Pd leads to magnetic order. Here we have investigated the change of the 4$f$ occupation in the substitution series CeRh$_{1-x}$Pd$_x$Sn for for $x$ = 0, 0.1, 0.3, 0.5, 0.75 by means of photoelectron spectroscopy with hard x-rays (HAXPES). The quantitative analysis of the core level spectra with a combined full multiplet and configuration interaction analysis shows a smooth decrease of the 4$f^0$ contribution with rising $x$ due to an increase of the effective 4$f$ binding energy $\varepsilon_{4f}$ and the reduction of the effective hybridization $V_\text{eff}$. We further compare valence band data with the calculated partial density of states and find that the Pd 4$d$ states are about 1eV further away from the Ce 4$f$ states at the Fermi energy than the Rh 4$d$ states. In fact, the effective binding energy $\varepsilon_{4f}$ of the 4$f$ states in the configuration interaction analysis of the core level spectra decreases by the same amount.

cond-mat.str-el↗

arXiv2021

Synthesis and study of transport and magnetic properties of magnesium cage compounds $R$Ni$_{2}$Mg$_{20}$ ($R$ = Pr and Nd)

We have synthesized magnesium cage compounds $R$Ni$_{2}$Mg$_{20}$ ($R$ = Pr and Nd). We report the measurements of electrical resistivity $ρ$, magnetic susceptibility $χ$, isothermal magnetization $M$, and specific heat $C$. Polycrystalline samples with $R$ = Pr and Nd were obtained by annealing, while the counterparts for $R$ = La, Ce, and Y were found to be absent. The $ρ(T)$ data for $R$ = Pr and Nd monotonically decrease on cooling from 300 K to 40 K and exhibit shoulders at around 13 K and 15 K, respectively. The Curie-Weiss behaviors of the $χ(T)$ data indicate the trivalent states of both the Pr and Nd ions. For $R$ = Pr, the maximum in $C(T)$ at around 7 K is reproduced by a doublet-triplet two-level model with an energy gap of 14 K. The peak in $C(T)$ at 0.7 K is attributed to a short-range order of quadrupolar degrees of freedom in the non-Kramers ground doublet. On the other hand, for $R$ = Nd, a maximum in $C(T)$ at around 9 K is explained by thermal excitation from a ground state doublet to an excited quartet separated by 23 K. Upon further cooling, $C(T)$ shows a lambda-shaped peak at 1.5 K. By applying magnetic fields up to 2 T, the peak becomes broad and shifts to higher temperatures, which is a characteristic of a ferromagnetic order.

cond-mat.str-el↗

arXiv2021

Field-angle-resolved landscape of non-Fermi-liquid behavior in the quasi-kagome Kondo Lattice CeRhSn

We have employed a magnetic field angle as a tuning parameter in a comprehensive measurement of the specific heat, magnetocaloric effect, and magnetization for the quasi-kagome Kondo lattice CeRhSn, which is considered to exhibit zero-field quantum criticality driven by geometrical frustration. By constructing the field-angle-resolved landscape of the entropy, we unexpectedly revealed that the non-Fermi-liquid nature survives up to a metamagnetic crossover field of roughly 3 T in the very narrow field-orientation range, close to the direction parallel to the quasi-kagome plane. We propose that spin fluctuations along the hexagonal $c$ axis are the dominant driving force for the non-Fermi-liquid behavior because it is strongly suppressed by a magnetic-field component along the $c$ axis. The multidimensional entropy landscape, which directly reflects the degeneracy of ground states, opens a new route for uncovering the nature of exotic phases in anisotropic systems.

cond-mat.str-el↗

arXiv2020

Simultaneous collapse of antiferroquadrupolar order and superconductivity in PrIr$_{2}$Zn$_{20}$ by nonhydrostatic pressure

Superconductivity in PrIr$_{2}$Zn$_{20}$ appears at $T_{\rm c} = 0.05$ K in the presence of an antiferroquadrupolar order below $T_{\rm Q} = 0.11$ K. We have studied pressure dependences of $T_{\rm c}$, $T_{\rm Q}$, and non-Fermi liquid behaviors in the resistivity $ρ(T)$ by using two pressure transmitting media: argon maintaining highly hydrostatic pressure, and glycerol, which solidifies above 5 GPa producing nonhydrostatic pressure. Upon applying $P$ with argon up to 10.6 GPa, $T_{\rm c}$ hardly changes, while $T_{\rm Q}$ monotonically increases from 0.11 to 0.23 K. With glycerol, however, $T_{\rm Q}$ and $T_{\rm c}$ simultaneously fall below 0.04 K at 6.3 GPa. The contrasting results indicate that onsite quadrupolar fluctuations induce superconductivity in this compound.

cond-mat.supr-con↗

arXiv2020

Pressure induced quenching of planar rattling in Cu$_{10}$Zn$_{2}$Sb$_{4}$S$_{13}$ studied by specific-heat and x-ray diffraction measurements

We have studied the pressure effect on the rattling of tetrahedrite Cu$_{10}$Zn$_{2}$Sb$_{4}$S$_{13\,}$(CZSS) and type-I clathrate Ba$_{8}$Ga$_{16}$Sn$_{30\,}$(BGS) by specific heat and x-ray diffraction measurements. By applying pressure $P$, the rattling energy for CZSS initially decreases and steeply increases for $P$ $\textgreater$ $1$ GPa. By contrast, the energy for BGS increases monotonically with $P$ up to 6.5 GPa. An analysis of the pressure dependent specific heat and x-ray diffraction indicates that the out-of-plane rattling of the Cu atoms in the S$_{3}$ triangle of CZSS originates from the chemical pressure, unlike the rattling of the Ba ions among off-center sites in an oversized cage of BGS. The rattling in CZSS ceases upon further increasing $P$ above 2 GPa, suggesting that Cu atoms escape away from the S$_{3}$ triangle plane.

cond-mat.mtrl-sci↗

arXiv2019

Hindered Quadrupole Order in PrMgNi4 with a Nonmagnetic Doublet Ground State

Structural, transport and magnetic properties of single-crystalline samples of a praseodymium-based cubic compound PrMgNi4 were studied. The single-crystal X-ray structural analysis revealed that Mg atoms are substituted for the Pr atoms at the 4a site by 4.5%. The chi(T) data follow the Curie-Weiss law with an effective moment for the Pr3+ ion. The magnetic specific heat divided by temperature, Cm/T, shows a broad maximum at around 3 K, which is reproduced by a two-level model with a ground state doublet. On cooling below 1 K, Cm/T approaches a constant value, which behavior is reproduced by a random two-level model. The twofold degeneracy of the ground state is lifted by symmetry lowering due to the substituted Mg atoms for the Pr atoms or strong hybridizations between the 4f2 electron states and conduction bands, which hinders the long-range quadrupole order.

cond-mat.str-el↗

arXiv2018

Linear dichroism in angle-resolved core-level photoemission spectra reflecting 4f ground-state symmetry of strongly correlated cubic Pr compounds

We report experimentally observed linear dichroism in angle-resolved core-level photoemission spectra of PrIr2Zn20 and PrB6 in cubic symmetry. The different anisotropic 4f charge distributions between the compounds due to the crystalline-electric-field splitting are responsible for the difference in the linear dichroism, which has been verified by spectral simulations with the full multiplet theory for a single-site Pr3+ ion in cubic symmetry. The observed linear dichroism and polarization-dependent spectra in two different photoelectron directions for PrIr2Zn20 are reproduced by theoretical analysis for the Gamma_3 ground state, whereas those of the Pr 3d and 4d core levels indicate the Gamma_5 ground state for PrB6.

cond-mat.str-el↗