arXiv subjects

Tetsuo Irifune

Publications and source records attributed to Tetsuo Irifune.

At least 19 recordsLinked to original sources

arXiv2025

Optically detected magnetic resonance of nitrogen-vacancy centers in microdiamonds inside nanopolycrystalline diamond anvil cell

We demonstrated optically detected magnetic resonance (ODMR) of nitrogen-vacancy (NV) centers in microdiamonds inside a diamond anvil cell pressurized with nanopolycrystalline diamond (NPD) anvils. NPD exhibits high optical transparency, superior hardness, and low thermal conductivity, making it suitable for optical and spectroscopic measurements under high-pressure and high-temperature conditions. We observed the ODMR signal from an ensemble of NV centers under conditions where NV centers in microdiamonds served as markers for pressures exceeding 30 GPa, with a culet diameter of 600 $\mu$m. We also performed ODMR measurements on multiple microdiamonds sealed inside a sample chamber and found that the resonance frequency varied with the pressure distribution. The combination of NPD and microdiamonds containing NV centers is auspicious for pressure and magnetic sensing under concurrent high-pressure and high-temperature conditions.

cond-mat.mtrl-sci↗

arXiv2025

Absence of higher than 6-fold coordination in glassy $GeO_{2}$ up to 158 GPa revealed by X-ray absorption spectroscopy

Simple binary oxide glasses can exhibit a compression behavior distinct from that of their crystalline counterparts. In this study, we employed high-pressure X-ray absorption spectroscopy coupled to the diamond anvil cell to investigate in detail local structural changes around Ge in glassy $GeO_{2}$ up to 158 GPa. We conducted four independent runs, both with and without pressure-transmitting media. Up to 30 GPa, we observed no significant influence of the pressure medium on the pressure dependence of the $Ge-O$ bond length ($ $). Between 10 and 30 GPa, the evolution of $ $ shows substantial variability across our experiments and previous works. The measured values lie close to those reported for crystalline polymorphs, including the rutile- and $CaCl_{2}$-type phase of $GeO_{2}$. This finding suggests that the amorphous structure possesses considerable flexibility to transition among different atomic configurations. From 30 GPa to 158 GPa, our results for both $ $ and the non-bonded cation-cation distance $ $ demonstrate that edge-sharing octahedra remain the main structural motives in glassy $GeO_{2}$. Up to 100 GPa, compaction proceeds primarily via distortions of octahedral $O-Ge-O$ bond angles accompanied by octahedral bond shortening. Above 100 GPa, octahedral distortion becomes the prevailing mechanism. Compared to its crystalline analogues ($\alpha-PbO_{2}$ and pyrite-like phase), glassy $GeO_{2}$ exhibits a slightly less efficient compaction mechanism, likely due to kinetic constraints that inhibit reconstructive lattice rearrangements.

cond-mat.mtrl-sci↗

arXiv2025

Enhancement of superconductivity on thin film of Sn under high pressure

We investigated the pressure effects of a superconductivity on thin films of Sn. Elemental superconductor Sn with a body-centered tetragonal structure, $\beta$-Sn, exhibits superconductivity below the superconducting transition temperature ($T_{\rm c}=3.72$ K) at ambient pressure. $T_{\rm c}$ of Sn increases with lowering dimension such as in thin film and nanowire growth, or by high-pressure application. For thin films, $T_{\rm c}$ exhibits a slight increase up to approximately 4 K compared to the bulk value, attributable to the crystalline size and lattice disorder. By applying pressure on a bulk Sn, $T_{\rm c}$ initially decreases from 3.72 K as the pressure increases. Further increasing pressure up to 10 GPa, $T_{\rm c}$ increases to 5.3 K with the structural transformation. However, the combination of these effects on thin films of Sn, namely, thin-film growth and pressure effects, remains underexplored. In this study, we combined film-growth and pressure-application techniques to further increase $T_{\rm c}$ using a diamond anvil cell with boron-doped diamond electrodes. The drop of the electrical resistance suggesting the onset of $T_{\rm c}$ on the thin film reached above 6 K in $\gamma$-Sn phase. Further, the upper critical magnetic field was drastically enhanced. Atomic force microscopy suggests that the refinement of the grain size of the thin film under the non-hydrostatic pressure conditions contributes to stabilizing the higher $T_{\rm c}$ of $\gamma$-Sn.

cond-mat.supr-con↗

arXiv2024

Local electronic properties of La3Ni2O7 under pressure

The recent discovery of superconductivity in $\rm La_3Ni_2O_7$ has attracted significant attention due to its high critical temperature and analogy to cuprate oxides. The oxidation and spin states of Ni ions are among the most important local properties in this compound, extensively discussed in the context of its superconductivity. Despite their direct link to the electron filling configurations of the relevant $\rm 3d_{x^2-y^2}$ and $\rm 3d_{z^2}$ orbitals, these local electronic properties of $\rm La_3Ni_2O_7$ yet to be systematically investigated. In this work, we address this issue using x-ray absorption spectroscopy (XAS) and x-ray emission spectroscopy (XES) measurements under pressure. Comparison of Ni \textit{K}-edge XAS and $\rm K\beta$ XES with the reference spectra of $\rm NiO$ and $\rm LaNiO_3$ shows that Ni ions, with an average valence of $\sim 2.53+$, are in a low-spin ($\rm S = 1/2$) ground state under ambient conditions. High pressure XAS and XES data clearly show that the oxidation ($\sim 2.5+$) and spin ($\rm S = 1/2$) states of Ni ions remain stable across the investigated pressure (up to 30 GPa) and temperature (down to 10 K) ranges, ruling out previously proposed spin transition scenarios.

cond-mat.supr-con↗

arXiv2024

Emergence of Superconductivity at 20 K in Th$_3$P$_4$-type In$_{3-x}$S$_4$ Synthesized by Diamond Anvil Cell with Boron-doped Diamond Electrodes

The exploration of superconductors in metastable phases by manipulating crystal structures through high-pressure techniques has attracted significant interest in materials science to achieve a high critical temperature ($T_c$). In this study, we report an emergence of novel superconductivity in a metastable phase of Th$_3$P$_4$-type cubic In$_{3-x}$S$_4$ with remarkably high $T_c$ at 20 K under 45 GPa by using an originally designed diamond anvil cell equipped with boron-doped diamond electrodes, which can perform a high-pressure synthesis and an in-situ electrical transport measurement simultaneously. In-situ structural analysis indicates that the In$_{3-x}$S$_4$ appears partially above 40 GPa without heating. The high-pressure annealing treatment induces complete transformation to the Th$_3$P$_4$-type structure, and the defected concentration of x in In$_{3-x}$S$_4$ decreases with increasing annealing temperature. The $T_c$ in In$_{3-x}$S$_4$ is maximized at x = 0 and approaches 20 K. Electronic band calculations show that the high density of states composed of sulfur and indium bands are located at the conduction band bottom near Fermi energy. The record high $T_c$ in In$_{3-x}$S$_4$ among superconducting sulfides accelerates the further exploration of high $T_c$ materials within the Th$_3$P$_4$-type cubic family by using flexibility in crystal structure.

cond-mat.supr-con↗

arXiv2022

Pushing the limits of flow strength in diamond

Extreme pressures and temperatures create conditions that allow even hard and brittle materials to deform plastically. Despite extensive research, the upper limits of flow strength, the resistance to plastic flow, remain uncertain, and the mechanisms driving deformation at the relevant stresses are a subject of debate. Using femtosecond in situ X-ray diffraction experiments and large-scale molecular dynamics simulations, we demonstrate that stacking fault-mediated strengthening enables shock-compressed nano-polycrystalline diamond to achieve a peak flow strength of 107+-5 GPa at a stress of 227+-8 GPa. Our findings show that extreme conditions can unlock unusual strength via mechanisms that can be used as design tools in targeted applications.

cond-mat.mtrl-sci↗

arXiv2022

High-pressure synthesis of superconducting Sn$_{3}$S$_{4}$ using diamond anvil cell with boron-doped diamond heater

High-pressure techniques open exploration of functional materials in broad research fields. An established diamond anvil cell with a boron-doped diamond heater and transport measurement terminals has performed the high-pressure synthesis of a cubic Sn$_{3}$S$_{4}$ superconductor. X-ray diffraction and Raman spectroscopy reveal that the Sn$_{3}$S$_{4}$ phase is stable in the pressure range of P>5 GPa in a decompression process. Transport measurement terminals in the diamond anvil cell detect a metallic nature and superconductivity in the synthesized Sn$_{3}$S$_{4}$ with a maximum onset transition temperature of 13.3 K at 5.6 GPa. The observed pressure-T$_{c}$ relationship is consistent with that from the first-principles calculation. The observation of superconductivity in Sn$_{3}$S$_{4}$ opens further materials exploration under high temperature and pressure conditions.

cond-mat.supr-con↗

arXiv2021

Diamond anvil cell with boron-doped diamond heater for high-pressure synthesis and in-situ transport measurements

Temperature and pressure are essential parameters in the synthesis, evaluation, and application of functional materials. This study proposes the addition of a heating function to a high-pressure diamond anvil cell (DAC) with in-situ measurement probes. The proposed DAC allows for simultaneous control of temperature and pressure within the sample space and can be used to synthesize functional materials under extreme conditions. The various components, namely the heater, thermometer, and measurement probes, were fabricated with a boron-doped diamond epitaxial film and could be used repeatedly. The developed DAC was used to successfully conduct the high-pressure annealing of La(O,F)BiS$_{2}$ single crystal and the high-pressure synthesis of EuFBiS$_{2}$ superconductors. The proposed technique shows promise for further exploration of superconductors to broaden the research field.

cond-mat.supr-con↗

arXiv2021

X-ray study of krypton and xenon under pressure reveals the mechanism of martensitic transformations

The martensitic transformation is a fundamental physical phenomenon at the origin of important industrial applications. However, the underlying microscopic mechanism, which is of critical importance to explain the outstanding mechanical properties of martensitic materials, is still not fully understood. This is because for most martensitic materials the transformation is a fast process that makes in situ studies extremely challenging. Noble solids krypton and xenon undergo a progressive pressure induced fcc to hcp martensitic transition with a very wide coexistence domain. Here, we took advantage of this unique feature to study the detailed mechanism of the transformation by employing in situ X-ray diffraction and absorption. We evidenced a four stages mechanism where the lattice mismatch between the fcc and hcp forms plays a key role in the generation of strain. We also determined precisely the effect of the transformation on the compression behavior of these materials.

cond-mat.mtrl-sci↗

arXiv2021

Pressure-induced superconductivity in TiGeTe$_{6}$

Layered ternary transition-metal chalcogenides have been focused as a vein of exploration for superconductors. In this study, TiGeTe$_{6}$ single crystals were synthesized and characterized by structural and valence state analyses and electrical transport measurements. The transport properties were measured under various pressures up to 71 GPa. The activation energy gets smaller as the applied pressure increases, and a signature of a pressure-induced metallization was observed under around 8.4 GPa. Under 13 GPa, pressure-induced superconductivity was discovered in this compound for the first time, with successive drops at 3 K and 6 K in the resistance, indicating the presence of multiple superconducting transitions. The superconducting transition temperature kept increasing as we further applied the pressure to the TiGeTe$_{6}$ single crystal in the performed pressure range, reaching as high as 8.1 K under 71 GPa.

cond-mat.supr-con↗

arXiv2020

Iodine molecule modifications with high pressure

Metallization and dissociation are key transformations in diatomic molecules at high densities particularly significant for modeling giant planets. Using X-ray absorption spectroscopy and atomistic modeling, we demonstrate that in halogens, the formation of a \textit{connected} molecular structure takes place at pressures well below metallization. Here we show that the iodine diatomic molecule first elongates of $\sim$0.007 Å~up to a critical pressure of $P_c$ $\backsim$7~GPa developing bonds between molecules. Then its length continuously decreases with pressure up to 15-20~GPa. Universal trends in halogens are shown and allow to predict for chlorine a pressure of 42$\pm$8~GPa for molecular bond-length reversal. Our findings tackle the molecule invariability paradigm in diatomic molecular phases at high pressures and may be generalized to other abundant diatomic molecules in the universe, including hydrogen.

physics.chem-ph↗

arXiv2020

Pressure-Induced Superconductivity in Layered Transition-metal Chalcogenides (Zr,Hf)GeTe$_{4}$ Explored by Data-driven Approach

Layered transition-metal chalcogenides (Zr,Hf)GeTe$_{4}$ were screened out from database of Atomwork as a candidate for pressure-induced superconductivity due to their narrow band gap and high density of state near the Fermi level. The (Zr,Hf)GeTe$_{4}$ samples were synthesized in single crystal and then the compositional ratio, crystal structures, and valence states were investigated via energy dispersive spectrometry, single crystal X-ray diffraction, and X-ray photoelectron spectroscopy, respectively. The pressure-induced superconductivity in both crystals were first time reported by using a diamond anvil cell with a boron-doped diamond electrode and an undoped diamond insulating layer. The maximum superconducting transition temperatures of ZrGeTe$_{4}$ and HfGeTe$_{4}$ were 6.5 K under 57 GPa and 6.6 K under 60 GPa, respectively.

cond-mat.supr-con↗

arXiv2020

Electrical transport measurements for superconducting sulfur hydrides using boron-doped diamond electrodes on beveled diamond anvil

A diamond anvil cell (DAC) which can generate extremely high pressure of multi-megabar is promising tool to develop a further physics such a high-transition temperature superconductivity. However, electrical transport measurements, which is one of the most important properties of such functional materials, using the DAC is quite difficult because the sample space is very small and a deformation of electrodes under extreme condition. In this study, we fabricated a boron-doped diamond micro-electrode and an undoped diamond insulation on a beveled culet surface of the diamond anvil. By using the developed DAC, we demonstrated the electrical transport measurements for sulfur hydride H$_2$S which known as a pressure-induced high-transition temperature superconducting H$_3$S at high pressure. The measurements were successfully conducted under high pressure up to 192 GPa, and then a multi-step superconducting transition composed from pure sulfur and some kinds of surfer hydrides, which is possible HS$_2$, was observed with zero resistance.

cond-mat.supr-con↗

arXiv2020

Mechanism of pressure induced amorphization of SnI4: a combined X-ray diffraction -- X-ray absorption spectroscopy study

We have studied the amorphization process of SnI4 up to 26.8GPa with unprecedented experimental details by combining Sn and I K edge X-ray absorption spectroscopy and powder X-ray diffraction. Standards and reverse Monte Carlo extended X-ray absorption fine structure (EXAFS) refinements confirm that the SnI4 tetrahedron is a fundamental structural unit that is preserved through the crystalline phase-I to crystalline phase-II transition about 7 to 10GPa and then in the amorphous phase that appears above 20GPa. Up to now unexploited Iodine EXAFS reveals to be extremely informative and confirms the formation of iodine iodine short bonds close to 2.85Å in the amorphous phase at 26.8 GPa. A coordination number increase of Sn in the crystalline phase-II appears to be excluded, while the deformation of the tetrahedral units proceeds through a flattening that keeps the average I-Sn-I angle close to 109.5°. Moreover, we put in evidence the impact of pressure on the Sn near edge structure under competing geometrical and electronic effects.

cond-mat.mtrl-sci↗

arXiv2019

Pressure-induced superconductivity in layered pnictogen diselenide NdO$_{0.8}$F$_{0.2}$Sb$_{1-x}$Bi$_x$Se$_2$ (x = 0.3 and 0.7)

Polycrystalline samples of layered pnictogen diselenide NdO0.8F0.2Sb1-xBixSe2 (x = 0 to 0.8) were successfully synthesized by solid-state reactions. Electrical resistivity in the synthesized samples was systematically decreased with an increase in Bi content x. Crystal structure analysis using synchrotron X-ray diffraction suggests that insulator to metal transition upon Bi doping correlates with anomalous change in c-axis length and/or corrugation in conducting layer. The emergence of superconductivity under high pressure is demonstrated using diamond anvil cell (DAC) with boron-doped diamond electrodes, for x = 0.3 and 0.7 as the representative samples. For Sb-rich one (x = 0.3), we observed a superconducting transition with Tconset = 5.3 K at 50 GPa, which is the first-ever report of the superconductivity in layered SbCh2-based (Ch: chalcogen) compounds. The Tconset of x = 0.3 increased with increasing pressure and reached 7.9 K at 70.8 GPa, followed by the gradual decrease in Tc up to 90 GPa. For Bi-rich one (x = 0.7), a superconducting transition with Tconset = 5.9 K was observed at 43.5 GPa, which is the almost comparable to that of x = 0.3; besides, upper critical field (Hc2) is evaluated to be ~10 T for x = 0.7, which is higher than that of x = 0.3 (Hc2 = 6.7 T at 50 GPa).

cond-mat.supr-con↗

arXiv2019

Data-driven Exploration of Pressure-Induced Superconductivity in AgIn$_{5}$Se$_{8}$

Candidates compounds for new thermoelectric and superconducting materials, which have narrow band gap and flat bands near band edges, were exhaustively searched by a high-throughput first-principles calculation from an inorganic materials database named AtomWork. We focused on AgIn$_{5}$Se$_{8}$ which has high density of state near the Fermi level. AgIn$_{5}$Se$_{8}$ was successfully synthesized as single crystals using a melt and slow cooling method. The single-crystal X-ray diffraction analysis revealed the obtained crystal is high quality without deficiencies. The valence states in AgIn$_{5}$Se$_{8}$ were determined to be Ag1+, In3+ and Se2- in accordance with a formal charge by the core level X-ray photoelectron spectroscopy analysis. The electrical resistance was evaluated under high pressure using a diamond anvil cell with boron-doped diamond electrodes. Although the sample was insulator with a resistance of above 40 MΩ at ambient pressure, the resistance markedly decreased with increase of the pressure, and a pressure-induced superconducting transition was discovered at 3.4 K under 52.5 GPa. The transition temperature increased up to 3.7 K under further pressure of 74.0 GPa.

cond-mat.supr-con↗

arXiv2019

Pressure-induced Superconductivity in Tin Sulfide

Tin sulfide (SnS) was successfully synthesized in single crystals by a melt and slow-cooling method. The obtained sample was characterized by an X-ray diffraction, an energy dispersive spectrometry, and an X-ray photoelectron spectroscopy. Electrical transport properties in SnS were investigated under high pressure using a diamond anvil cell with boron-doped metallic diamond electrodes and undoped diamond insulating layer. We successfully observed an insulator to metal transition from 12.5 GPa and pressure-induced superconductivity at 5.8 K under 47.8 GPa as predicted by a theoretical calculation.

cond-mat.supr-con↗

arXiv2018

Pressure-induced Insulator to Metal Transition of Mixed Valence Compound Ce(O,F)SbS$_{2}$

Transport properties of Ce$_{0.85}$F0.15SbS$_{2}$ and undoped CeOSbS$_{2}$ under high pressure were investigated experimentally and theoretically. Electrical resistivity measurements of the Ce$_{0.85}$F0.15SbS$_{2}$ single crystals were performed under various high pressures using a diamond anvil cell with boron-doped diamond electrodes. The samples showed the insulator to metal transition by applying high pressure up to 30-40 GPa. On the other hand, the undoped CeOSbS$_{2}$ showed almost same transport property with the F-doped sample under high pressure. The valence state analysis using X-ray photoelectron spectroscopy revealed a simple valence state of Ce3+ in Ce$_{0.85}$F0.15SbS$_{2}$ and mixed valence state between Ce3+ and Ce4+ in undoped CeOSbS$_{2}$. The valence fluctuation in Ce carried out the comparable transport nature in the both samples. A band calculation suggests that the undoped CeOSbS$_{2}$ could be metallic under high pressure of 30 GPa in accordance with the experimental results. A superior thermoelectric property of power factor in CeOSbS$_{2}$ was estimated under high pressure around 20 GPa in comparison with that of ambient pressure.

cond-mat.mtrl-sci↗