Piston-cylinder cell made of Ni-Cr-Al alloy for magnetic susceptibility measurements under high pressures in pulsed high magnetic fields.

We developed a metallic pressure cell made of 56Ni-40Cr-4Al (Ni-Cr-Al) alloy for use with a non-destructive pulse magnet and a magnetic susceptibility measurement apparatus with a proximity detector oscillator (PDO) in pulsed magnetic fields of up to 51 T under pressures of up to 2.1 GPa. Both the sample and sensor coil of the PDO were placed in the cell so that the magnetic signal from Ni-Cr-Al would not overlay the intrinsic magnetic susceptibility of the sample.

Destabilization of the Charge Density Wave and the Absence of Superconductivity in ScVSn under High Pressures up to 11 GPa.

VSn ( = Sc, Y, or rare earth) is a new family of kagome metals that have a similar vanadium structural motif as VSb ( = K, Rb, Cs) compounds. Unlike VSb, ScVSn is the only compound among the series of VSn that displays a charge density wave (CDW) order at ambient pressure, yet it shows no superconductivity (SC) at low temperatures. Here, we perform a high-pressure transport study on the ScVSn single crystal to track the evolutions of the CDW transition and to explore possible SC.

Anharmonic phonon interactions and the Kondo effect in a FeSe/SbTe/FeSe heterostructure: a proximity effect between ferromagnetic chalcogenide and di-chalcogenide.

In this report, we have introduced magnetic ordering into the nontrivial system of conventional topological insulators (TIs) by creating magnetic interfaces. In this context, antimony di-chalcogenide SbTe sandwiched between two thin layers of FeSe was prepared using the pulsed laser deposition (PLD) technique. The prepared heterostructure demonstrated good crystallinity along with homogeneous morphology displaying pyramid-shaped characteristic triangular islands.

Pressure-Induced Superconductivity of the Quasi-One-Dimensional Organic Conductor (TMTTF)TaF.

We investigated the superconductivity of (TMTTF)TaF (TMTTF: tetramethyl-tetrathiafulvalene) by conducting resistivity measurements under high pressure up to 8 GPa. A cubic anvil cell (CAC) pressure generator, which can produce hydrostatic high-pressure, was used for this study. Since the generalized temperature-pressure (-) diagram of (TMTF) ( = Se, S, : monovalent anion) based on (TMTTF)PF ( = 70 K and spin-Peierls: SP, = 15 K) was proposed by Jérome, exploring superconductivity states using high-pressure measurement beyond 4 GPa has been required to confirm the universality of the electron-correlation variation under pressure in (TMTTF) (TMTTF)TaF, which has the largest octahedral-symmetry counter anion TaF in the (TMTTF) series, possesses the highest charge-ordering (CO) transition temperature ( = 175 K) in (TMTTF) and demonstrates an anti-ferromagnetic transition ( = 9 K) at ambient pressure.

Evidence for pressure induced unconventional quantum criticality in the coupled spin ladder antiferromagnet CHNCuBr.

Quantum phase transitions in quantum matter occur at zero temperature between distinct ground states by tuning a nonthermal control parameter. Often, they can be accurately described within the Landau theory of phase transitions, similarly to conventional thermal phase transitions. However, this picture can break down under certain circumstances.

Nearly Room-Temperature Ferromagnetism in a Pressure-Induced Correlated Metallic State of the van der Waals Insulator CrGeTe_{3}.

A complex interplay of different energy scales involving Coulomb repulsion, spin-orbit coupling, and Hund's coupling energy in 2D van der Waals (vdW) material produces a novel emerging physical state. For instance, ferromagnetism in vdW charge transfer insulator CrGeTe_{3} provides a promising platform to simultaneously manipulate the magnetic and electrical properties for potential device implementation using few nanometers thick materials. Here, we show a continuous tuning of magnetic and electrical properties of a CrGeTe_{3} single crystal using pressure.

Pressure Dependence of Superconducting Properties, Pinning Mechanism, and Crystal Structure of the FeMnSeTe Superconductor.

We have investigated the pressure () effect on structural (up to 10 GPa), transport [(): up to 10 GPa], and magnetic [((): up to 1 GPa)] properties and analyzed the flux pinning mechanism of the FeMnSeTe superconductor. The maximum superconducting transition temperature ( ) of 22 K with the coefficient of d /d = +2.6 K/GPa up to 3 GPa (d /d = -3.

Continuous control of classical-quantum crossover by external high pressure in the coupled chain compound CsCuCl.

In solid materials, the parameters relevant to quantum effects, such as the spin quantum number, are basically determined and fixed at the chemical synthesis, which makes it challenging to control the amount of quantum correlations. We propose and demonstrate a method for active control of the classical-quantum crossover in magnetic insulators by applying external pressure. As a concrete example, we perform high-field, high-pressure measurements on CsCuCl, which has the structure of weakly-coupled spin chains.

Defect induced ferromagnetic ordering and room temperature negative magnetoresistance in MoTeP.

The magneto-transport, magnetization and theoretical electronic-structure have been investigated on type-II Weyl semimetallic MoTeP. The ferromagnetic ordering is observed in the studied sample and it has been shown that the observed magnetic ordering is due to the defect states. It has also been demonstrated that the presence of ferromagnetic ordering in effect suppresses the magnetoresistance (MR) significantly.

Fabrication and evaluation via nuclear quadrupole resonance of a palm cubic-anvil pressure cell.

A "palm" cubic-anvil pressure cell (PCAC) having an outer diameter of 60 mm, the smallest cubic-anvil cell to date, was fabricated to insert in a large-bore superconducting magnet. The pressure cell has a sample space of ϕ 2.5 × 1.

New phenomena of photo-luminescence and persistent luminescence of a Eu,Tb codoped CaBaPO phosphor under high hydrostatic pressure.

In this study, we present a photo-luminescence (PL) and persistent luminescence (PersL) investigation of Ca6BaP4O17:Eu2+,Tb3+ (CBPO:Eu,Tb) at high hydrostatic pressure in the range of 0-11.04 GPa. More importantly, there is a significant increase of PL intensity and extension of PersL duration time at a pressure point of ∼0.

Superconducting-Gap Anisotropy of Iron Pnictides Investigated via Combinatorial Microwave Measurements.

One of the most significant issues for superconductivity is clarifying the momentum-dependent superconducting gap Δ([Formula: see text]), which is closely related to the pairing mechanism. To elucidate the gap structure, it is essential to investigate Δ([Formula: see text]) in as many different physical quantities as possible and to crosscheck the results obtained in different methods with each other. In this paper, we report a combinatorial investigation of the superfluid density and the flux-flow resistivity of iron-pnictide superconductors; LiFeAs and BaFe(AsP) (x = 0.

Pressure effect on the magnetoresistivity of topological semimetal RhSn.

RhSn is a topological semimetal with chiral fermions. At ambient pressure, it exhibits large positive magnetoresistance (MR) and field-induced resistivity upturn at low temperatures. Here we report on the electrical transport properties of RhSn single crystal under various pressures.

Redetermination of the crystal structure of Si ( = Pr, Nd) from single-crystal X-ray diffraction data.

The crystal structures of praseodymium silicide (5/4), PrSi, and neodymium silicide (5/4), NdSi, were redetermined using high-quality single-crystal X-ray diffraction data. The previous structure reports of PrSi were only based on powder X-ray diffraction data [Smith (1967 ▸). 940-943; Yang (2002 ▸).

Novel excitations near quantum criticality in geometrically frustrated antiferromagnet CsFeCl.

The investigation of materials that exhibit quantum phase transition provides valuable insights into fundamental problems in physics. We present neutron scattering under pressure in a triangular-lattice antiferromagnet that has a quantum disorder in the low-pressure phase and a noncollinear structure in the high-pressure phase. The neutron spectrum continuously evolves through critical pressure; a single mode in the disordered state becomes soft with the pressure and it splits into gapless and gapped modes in the ordered phase.

Pressure-induced hydrogen localization coupled to a semiconductor-insulator transition in a hydrogen-bonded molecular conductor.

Purely organic crystals, κ-X(Cat-EDT-TTF) [X = H or D, Cat-EDT-TTF = catechol-fused tetrathiafulvalene], are a new type of molecular conductor with hydrogen dynamics. In this work, hydrostatic pressure effects on these materials were investigated in terms of the electrical resistivity and crystal structure. The results indicate that the pressure induces and promotes hydrogen (deuterium) localization in the hydrogen bond, in contrast to the case of the conventional hydrogen-bonded materials (where pressure prevents hydrogen localization), and consequently leads to a significant change in the electrical conducting properties (.

Pressure-induced phase transitions and superconductivity in a black phosphorus single crystal.

We report a thorough study of the transport properties of the normal and superconducting states of black phosphorus (BP) under magnetic field and high pressure with a large-volume apparatus that provides hydrostatic pressure to induce transitions from the layered A17 phase to the layered A7 phase and to the cubic phase of BP. Quantum oscillations can be observed at ≥ 1 GPa in both resistivity and Hall voltage, and their evolutions with pressure in the A17 phase imply a continuous enlargement of Fermi surface. A significantly large magnetoresistance (MR) at low temperatures is observed in the A7 phase that becomes superconducting below a superconducting transition temperature ∼ 6-13 K.

Pressure-induced coherent sliding-layer transition in the excitonic insulator TaNiSe.

The crystal structure of the excitonic insulator TaNiSe has been investigated under a range of pressures, as determined by the complementary analysis of both single-crystal and powder synchrotron X-ray diffraction measurements. The monoclinic ambient-pressure excitonic insulator phase II transforms upon warming or under a modest pressure to give the semiconducting -centred orthorhombic phase I. At higher pressures ( >3 GPa), transformation to the primitive orthorhombic semimetal phase III occurs.

Emergence of a new valence-ordered structure and collapse of the magnetic order under high pressure in EuPtP.

The layered hexagonal EuPtP is a rare substance that exhibits two successive valence transitions occurring simultaneously with valence ordering transitions and an antiferromagnetic order. Anticipating that the application of pressure to this sample would induce a new valence-ordered structure and/or a new phenomenon associated with valence fluctuation, we examined the electrical resistivity ρ, the Eu L-edge x-ray absorption spectroscopy, and the powder x-ray diffraction under high pressure. We found a new valence transition at around P  =  2.

Iron arsenides with three-dimensional FeAs layer networks: Ca(FePt)PtAs (n = 2, 3).

We report the comprehensive studies between synchrotron X-ray diffraction, electrical resistivity and magnetic susceptibility experiments for the iron arsenides Ca(FePt)PtAs for n = 2 and 3. Both structures crystallize in the monoclinic space group P2/m (#11) with three-dimensional FeAs structures. The horizontal FeAs layers are bridged by inclined FeAs planes through edge-sharing FeAs5 square pyramids, resulting in triangular tunneling structures rather than the simple layered structures found in conventional iron arsenides.

Magnetic Precursor of the Pressure-Induced Superconductivity in Fe-Ladder Compounds.

The pressure effects on the antiferromagentic orders in iron-based ladder compounds CsFe_{2}Se_{3} and BaFe_{2}S_{3} have been studied using neutron diffraction. With identical crystal structure and similar magnetic structures, the two compounds exhibit highly contrasting magnetic behaviors under moderate external pressures. In CsFe_{2}Se_{3} the ladders are brought much closer to each other by pressure, but the stripe-type magnetic order shows no observable change.

HEAVY FERMIONS. Strange metal without magnetic criticality.

A fundamental challenge to our current understanding of metals is the observation of qualitative departures from Fermi liquid behavior. The standard view attributes such non-Fermi liquid phenomena to the scattering of electrons off quantum critical fluctuations of an underlying order parameter. Although the possibility of non-Fermi liquid behavior isolated from the border of magnetism has long been speculated, no experimental confirmation has been made.