arXiv subjects

Takahiro Matsuoka

Publications and source records attributed to Takahiro Matsuoka.

11 recordsLinked to original sources

arXiv2026

$α$-RuCl$_3$ intercalated into graphite: a new three-dimensional platform for exotic quantum phases

Multilayer graphene with different stacking sequences has emerged as a powerful setting for correlated and topological phases. In parallel, progress in graphene heterostructures with magnetic or correlated materials-most notably the Kitaev candidate $α$-RuCl$_3$-has demonstrated charge transfer, magnetic proximity effects, and interfacial reconstruction, creating new opportunities for engineered quantum systems. Motivated by these developments, we explore a three-dimensional analogue in which $α$-RuCl$_3$ layers are inserted directly into the van der Waals gaps of graphite, forming an intercalated system. Here, we report the successful synthesis and comprehensive characterization of graphite intercalated with $α$-RuCl$_3$. Using a combination of X-ray diffraction, quantum oscillation measurements, and first-principles electronic structure calculations, we study the structural and electronic properties of these intercalated crystals. Our results demonstrate that graphite intercalated with $α$-RuCl$_3$ offers a robust route to develop three-dimensional materials with access to novel correlated and topological states.

cond-mat.str-el↗

arXiv2026

Bulk superconductivity up to 96 K in pressurized nickelate single crystals

Recently, the Ruddlesden-Popper bilayer nickelate $La_3Ni_2O_7$ has emerged as a superconductor with a transition temperature ($T_c$) of approximately 80 K above 14 GPa (Refs. 1-3). Achieving higher $T_c$ in nickelate superconductors, along with the synthesis of reproducible high-quality single crystals without relying on high-oxygen-pressure growth conditions, remains a significant challenge$^{[4-7]}$. Here we report superconductivity up to 96 K under high pressure in bilayer nickelate single crystals synthesized at ambient pressure. Energy-dispersive spectroscopy, single-crystal X-ray diffraction, nuclear quadrupole resonance and scanning transmission electron microscopy evidenced high crystal quality of the flux-grown $La_2SmNi_2O_{7-δ}$ single crystals. $La_2SmNi_2O_7$ exhibits clear bulk superconductivity, including zero resistivity ($T_{c,max}^{onset}$ = 92 K and $T_{c,max}^{zero}$ = 73 K at 21.6 GPa) and the Meissner effect ($T_c$= 60 K at 20.6 GPa). A low-temperature high-pressure structural study indicates that both monoclinic and tetragonal structures can support superconductivity in this bilayer nickelate. Furthermore, we established a correlation between higher $T_c$ under high pressures and larger in-plane lattice distortion under ambient conditions, corroborated by observing even higher $T_c^{onset}$ of 96 K in $La_{1.57}Sm_{1.43}Ni_2O_{7-δ}$. This study overcomes key limitations in growing nickelate superconductor crystals, resolves the crystal structure in the superconducting state and demonstrates an effective pathway towards achieving higher $T_c$.

cond-mat.supr-con↗

arXiv2026

Reply to "Threefold error in the reported zero-field cooled magnetic moment of single crystal $La_2SmNi_2O_7$ (arXiv: 2602.23240)"

We respond to the critique by Aleksandr V. Korolev and Evgeny F. Talantsev on the superconducting phase fraction ($f$) calculations in Li et al. Nature 649, 871-878 (2026). First, the weak upturn in the low-temperature tail of our data has been confirmed to originate from the background, and the paramagnetic Meissner effect is absent in our case; thus, field-cooled (FC) data can be used for superconducting phase fraction calculations. Second, demagnetization effect must be calculated based on the actual measured moment as a function of $f$, which has been well-established and routinely employed in the superconductivity community. In contrast, Korolev and Talantsev treated the demagnetization field as a constant; thus, their calculation underestimates $f$ by a factor of $(1-Nχ_{meas})(1-N)$. This factor is close to 1/3, given $N$ = 0.849, $χ_{meas}$ = -1.313 in our study, which explains the origin of their deviated result (nearly three times smaller than our results). Third, our sample is a homogeneous high-quality bulk single crystal, evidenced by various techniques, making the existence of multiple discrete superconducting regions highly unlikely. We conclude that the superconducting phase fraction calculations reported in Li et al. Nature 649, 871-878 (2026) are not invalidated by the analyses presented in Korolev et al. arXiv: 2602.23240 (2026).

cond-mat.supr-con↗

arXiv2023

Topological Nernst and topological thermal Hall effect in rare-earth kagome ScMn$_6$Sn$_6$

Thermal and thermoelectric measurements are known as powerful tools to uncover the physical properties of quantum materials due to their sensitivity towards the scattering and chirality of heat carriers. We use these techniques to confirm the presence of momentum and real-space topology in ScMn$_6$Sn$_6$. There is an unconventional dramatic increase in the Seebeck coefficient on entering the transverse conical spiral (TCS) below $T$ = 200 K suggesting an unusual scattering of heat carriers. In addition, the observed anomalous thermal Hall effect and the anomalous Nernst effect indicates non-zero Berry curvature in $k$-space. Furthermore, we identify a significant topological contribution to the thermal Hall and Nernst signals in the TCS phase revealing the impacts of real-space Berry curvature. We discuss the presence of topological thermal Hall effect and topological Nernst effect for the first time in the diverse HfFe$_6$Ge$_6$ family. This study illustrates the importance of transverse thermal and thermoelectric measurements to investigate the origin of topological transport in the non-coplanar magnetic phases in this family of kagome metals.

cond-mat.str-el↗

arXiv2023

Pressure-Induced Insulator-to-Metal Transition in van der Waals compound CoPS$_3$

We have studied the insulator-to-metal transition and crystal structure evolution under high pressure in the van der Waals compound CoPS$_3$ through $\textit{in-situ}$ electrical resistance, Hall resistance, magnetoresistance, X-ray diffraction, and Raman scattering measurements. CoPS$_3$ exhibits a $C2/m$ $\rightarrow$ $P\overline{3}$ structural transformation at 7 GPa accompanied by a 2.9$\%$ reduction in the volume per formula unit. Concomitantly, the electrical resistance decreases significantly, and CoPS$_3$ becomes metallic. This metallic CoPS$_3$ is a hole-dominant conductor with multiple conduction bands. The linear magnetoresistance and the small volume collapse at the metallization suggest the incomplete high-spin $\rightarrow$ low-spin transition in the metallic phase. Thus, the metallic CoPS$_3$ possibly possesses an inhomogeneous magnetic moment distribution and short-range magnetic ordering. This report summarizes the comprehensive phase diagram of $M$PS$_3$ ($M$ = V, Mn, Fe, Co, Ni, and Cd) that metalize under pressures.

cond-mat.str-el↗

arXiv2022

Charge density wave in kagome lattice intermetallic ScV6Sn6

Materials hosting kagome lattices have drawn interest for the diverse magnetic and electronic states generated by geometric frustration. In the $A$V$_3$Sb$_5$ compounds ($A$ = K, Rb, Cs), stacked vanadium kagome layers give rise to unusual charge density waves (CDW) and superconductivity. Here we report single-crystal growth and characterization of ScV$_6$Sn$_6$, a hexagonal HfFe$_6$Ge$_6$-type compound that shares this structural motif. We identify a first-order phase transition at 92 K. Single crystal X-ray and neutron diffraction reveal a charge density wave modulation of the atomic lattice below this temperature. This is a distinctly different structural mode than that observed in the $A$V$_3$Sb$_5$ compounds, but both modes have been anticipated in kagome metals. The diverse HfFe$_6$Ge$_6$ family offers more opportunities to tune ScV$_6$Sn$_6$ and explore density wave order in kagome lattice materials.

cond-mat.str-el↗

arXiv2021

Pressure-induced insulator-metal transition in two-dimensional Mott insulator NiPS3

The pressure-induced insulator to metal transition (IMT) of layered magnetic nickel phosphorous tri-sulfide NiPS3 was studied in-situ under quasi-uniaxial conditions by means of electrical resistance (R) and X-ray diffraction (XRD) measurements. This sluggish transition is shown to occur at 35 GPa. Transport measurements show no evidence of superconductivity to the lowest measured temperature (~ 2 K). The structure results presented here differ from earlier in-situ work that subjected the sample to a different pressure state, suggesting that in NiPS3 the phase stability fields are highly dependent on strain. It is suggested that careful control of the strain is essential when studying the electronic and magnetic properties of layered van der Waals solids.

cond-mat.str-el↗

arXiv2020

Beryllium Polyhydride Be4H8(H2)2 Synthesized at HP/HT

We report the XRD and Raman scattering measurements in combination with DFT calculations that reveal the formation of beryllium polyhydride Be4H8(H2)2 by laser heating Be/H2 mixture to above 1700 K at pressures between 5 GPa and 8 GPa. The Be4H8(H2)2 crystallizes in a P6_3/mmc structure and consists of corner-sharing BeH4 tetrahedrons and H2 molecules that are in an interstitial site. The Be4H8(H2)2 is stable at least to 14 GPa on compression and stable down to 4 GPa at room temperature. Our ab-initio calculations suggest that the Be4H8(H2)2 is a meta-stable phase of Be-H system.

cond-mat.mtrl-sci↗

arXiv2019

Hydrogen-Storing Salt NaCl(H$_2$) Synthesized at High Pressure and High Temperature

X-ray diffraction and Raman scattering measurements, and first-principles calculations are performed to search for the formation of NaCl-hydrogen compound. When NaCl and H$_{2}$ mixture is laser-heated to above 1500 K at pressures exceeding 40 GPa, we observed the formation of NaClH$_{\textit{x}}$ with $\textit{P}$6$_{3}$/$\textit{mmc}$ structure which accommodates H$_{2}$ molecules in the interstitial sites of NaCl lattice forming ABAC stacking. Upon the decrease of pressure at 300 K, NaClH$_\textit{x}$ remains stable down to 17 GPa. Our calculations suggest the observed NaClH$_{\textit{x}}$ is NaCl(H$_{2}$). Besides, a hydrogen-richer phase NaCl(H$_{2}$)$_{4}$ is predicted to become stable at pressures above 40 GPa.

cond-mat.mtrl-sci↗

arXiv2018

Superconductivity of platinum hydride

We report the ac magnetic susceptibility, electrical resistance, and X-ray diffraction measurements of platinum hydride (PtHx) in diamond anvil cells, which reveal its superconducting transition. At 32 GPa, when PtHx is in a P63/mmc structure, PtHx exhibits superconducting transition at 6.7 K and superconducting transition temperature (Tc) decreases with pressure to 4.8 K at 36 GPa. The observed T c is higher than that of powdered Pt by more than three orders of magnitude. It is suggested that hydrides of noble metals have higher Tc than the elements.

cond-mat.supr-con↗

arXiv2009

Pressure-induced Superconductivity in Crystalline Boron Nanowires

We report high-pressure induced superconductivity in boron nanowires (BNWs) with rhombohedral crystal structure. Obviously different from bulk rhombohedral boron, these BNWs show a semiconductor-metal transition at much lower pressure than bulk boron. Also, we found these BNWs become superconductors with Tc=1.5 K at 84 GPa, at the pressure of which bulk boron is still a semiconductor, via in-situ resistance measurements in a diamond anvil cell. With increasing pressure, Tc of the BNWs increases. The occurrence of superconductivity in the BNWs at a pressure as low as 84 GPa probably arises from the size effect.

cond-mat.supr-con↗