High-pressure phase diagrams of FeSe1-xTex: correlation between suppressed nematicity and enhanced superconductivity.

The interplay among magnetism, electronic nematicity, and superconductivity is the key issue in strongly correlated materials including iron-based, cuprate, and heavy-fermion superconductors. Magnetic fluctuations have been widely discussed as a pairing mechanism of unconventional superconductivity, but recent theory predicts that quantum fluctuations of nematic order may also promote high-temperature superconductivity. This has been studied in FeSe1-xSx superconductors exhibiting nonmagnetic nematic and pressure-induced antiferromagnetic orders, but its abrupt suppression of superconductivity at the nematic end point leaves the nematic-fluctuation driven superconductivity unconfirmed. Here we report on systematic studies of high-pressure phase diagrams up to 8 GPa in high-quality single crystals of FeSe1-xTex. When Te composition x(Te) becomes larger than 0.1, the high-pressure magnetic order disappears, whereas the pressure-induced superconducting dome near the nematic end point is continuously found up to x(Te) ≈ 0.5. In contrast to FeSe1-xSx, enhanced superconductivity in FeSe1-xTex does not correlate with magnetism but with the suppression of nematicity, highlighting the paramount role of nonmagnetic nematic fluctuations for high-temperature superconductivity in this system.

Strong polarization switching with low-energy loss in hydrogen-bonded organic antiferroelectrics.

The electric-field-induced phase transition from antipolar to polar structures is at the heart of antiferroelectricity. We demonstrate direct evidence of antiferroelectricity by applying a strong electric field to two antipolar crystals of squaric acid (SQA) and 5,5'-dimethyl-2,2'-bipyridinium chloranilate. The field-induced polarization of SQA is quite large and reasonably explained by the theoretically calculated polarization on the hydrogen-bonded sheet sublattice. The pseudo-tetragonal lattice of SQA permits unique switching topologies that produce two different ferroelectric phases of low and high polarizations. By tilting the applied field direction, the electrical switching mechanism can be attributed to a 90° rotation of the sheet polarization. From the viewpoint of applications, the strong polarization, high switching field, and quite slim hysteresis observed in the polarization versus electric field curve for SQA are advantageous for excellent-efficiency energy storage devices.

Cluster-Based Haldane State in an Edge-Shared Tetrahedral Spin-Cluster Chain: Fedotovite K_{2}Cu_{3}O(SO_{4})_{3}.

Fedotovite K_{2}Cu_{3}O(SO_{4})_{3} is a candidate of new quantum spin systems, in which the edge-shared tetrahedral (EST) spin clusters consisting of Cu^{2+} are connected by weak intercluster couplings forming a one-dimensional array. Comprehensive experimental studies by magnetic susceptibility, magnetization, heat capacity, and inelastic neutron scattering measurements reveal the presence of an effective S=1 Haldane state below T≅4 K. Rigorous theoretical studies provide an insight into the magnetic state of K_{2}Cu_{3}O(SO_{4})_{3}: an EST cluster makes a triplet in the ground state and a one-dimensional chain of the EST induces a cluster-based Haldane state. We predict that the cluster-based Haldane state emerges whenever the number of tetrahedra in the EST is even.

Crystallization and vitrification of electrons in a glass-forming charge liquid.

Charge ordering (CO) is a phenomenon in which electrons in solids crystallize into a periodic pattern of charge-rich and charge-poor sites owing to strong electron correlations. This usually results in long-range order. In geometrically frustrated systems, however, a glassy electronic state without long-range CO has been observed. We found that a charge-ordered organic material with an isosceles triangular lattice shows charge dynamics associated with crystallization and vitrification of electrons, which can be understood in the context of an energy landscape arising from the degeneracy of various CO patterns. The dynamics suggest that the same nucleation and growth processes that characterize conventional glass-forming liquids guide the crystallization of electrons. These similarities may provide insight into our understanding of the liquid-glass transition.

Spin-orbital superstructure in strained ferrimagnetic perovskite cobalt oxide.

We have investigated the Co-3d spin-orbital state in a thin film of perovskite LaCoO3 to clarify the origin of strain induced spontaneous magnetization (T(C)=94 K) by means of x-ray diffraction, optical spectroscopy, and magnetization measurements. A lattice distortion with the propagation vector (1/4 -1/4 1/4) and an anomalous activation of optical phonons coupled to Co-3d orbital are observed below 126 K. Combined with the azimuthal angle analysis of superlattice reflection, we propose that the ordering of Co-3d orbital promoted by an epitaxial strain produces a unique ferrimagnetic structure.

Giant Rashba-type spin splitting in bulk BiTeI.

There has been increasing interest in phenomena emerging from relativistic electrons in a solid, which have a potential impact on spintronics and magnetoelectrics. One example is the Rashba effect, which lifts the electron-spin degeneracy as a consequence of spin-orbit interaction under broken inversion symmetry. A high-energy-scale Rashba spin splitting is highly desirable for enhancing the coupling between electron spins and electricity relevant for spintronic functions. Here we describe the finding of a huge spin-orbit interaction effect in a polar semiconductor composed of heavy elements, BiTeI, where the bulk carriers are ruled by large Rashba-like spin splitting. The band splitting and its spin polarization obtained by spin- and angle-resolved photoemission spectroscopy are well in accord with relativistic first-principles calculations, confirming that the spin splitting is indeed derived from bulk atomic configurations. Together with the feasibility of carrier-doping control, the giant-Rashba semiconductor BiTeI possesses excellent potential for application to various spin-dependent electronic functions.

Pseudogap of metallic layered nickelate R(2-x)Sr(x)NiO4 (R = Nd, Eu) crystals measured using angle-resolved photoemission spectroscopy.

We have investigated charge dynamics and electronic structures for single crystals of metallic layered nickelates, R(2-x)Sr(x)NiO4 (R = Nd, Eu), isostructural to La(2-x)Sr(x)CuO4. Angle-resolved photoemission spectroscopy on the barely metallic Eu(0.9)Sr(1.1)NiO4 (R = Eu, x = 1.1) has revealed a large hole surface of x2-y2 character with a high-energy pseudogap of the same symmetry and comparable magnitude with those of underdoped (x<0.1) cuprates, although the antiferromagnetic interactions are 1 order of magnitude smaller. This finding strongly indicates that the momentum-dependent pseudogap feature in the layered nickelate arises from the real-space charge correlation.

Electric-field control of solitons in a ferroelectric organic charge-transfer salt.

The role of solitons in transport, dielectric, and magnetic properties has been revealed for the quasi-one-dimensional organic charge-transfer salt, TTF-QBrCl3 [tetrathiafulvalene (TTF)-2-bromo-3,5,6-trichloro-p-benzoquinone (QBrCl3)]. The material was found to be ferroelectric and hence the solitons should be located at the boundary of the segments with opposite electric polarization. This feature enabled the electric-field control of soliton density and hence the clear-cut detection of soliton contributions. The gigantic dielectric response in the ferroelectric phase is ascribed to the dynamical bound and creeping motions of spinless solitons.

Magnetic field switching between the two orbital-ordered states in DyVO3.

The critical phase competition between different spin-orbital-ordered states has been investigated for the DyVO3 single crystal. As temperature is lowered, the compound exhibits a reentrant spin and orbital ordering (SO and OO) transition: C-->G-->C type for SO and G-->C-->G type for OO. It was found that a magnetic field also drives the phase transition from C to G for OO and concomitantly from G to C for SO, the latter of which is coupled with the metamagnetic transition of the Dy 4f moments. The mechanism of this novel magnetic-field-induced orbital switching is discussed.

Ferroelectric valence transition and phase diagram of a series of charge-transfer complexes of 4,4'-dimethyltetrathiafulvalene and tetrahalo-p-benzoquinones.

Variation of the ferroelectric phase transition has been investigated for a series of isomorphous donor (D)-acceptor (A) charge-transfer complexes composed of 4,4'-dimethyltetrathiafulvalene (DMTTF) and tetrahalo-p-benzoquinones by measurements of dielectric susceptibility, X-ray diffraction, and infrared molecular vibrational spectra. The neutral-ionic phase transition of DMTTF-p-chloranil at 65 K accompanies a dielectric peak anomaly associated with the DA stack dimerization. Successive halogen replacement by bromine in the component tetrahalo-p-benzoquinone molecule expands the lattice along the DA stack of the DMTTF complex, and reduces the critical temperature steeply toward zero temperature in an analogous way to the critical behavior of quantum ferroelectrics. The 2,6-dibromo-substituted compound showing the behavior of the quantum paraelectricity is located in the immediate vicinity of the quantum critical point of this phase diagram as signified also by enhancement of the ionicity, the dielectric susceptibility, and the dynamical dimeric distortion at the lowest temperature.

Neutral-ionic phase separation and one-dimensional ferroelectricity in organic relaxors

Microscopic phase segregation by chemical doping and resultant anomalous dielectric response have been investigated for tetrathiafulvalene-p-chloranil complex doped with trichloro-p-benzoquinone ( QCl3). Beyond a critical QCl3 content, the system shows a behavior of relaxor ferroelectrics, as characterized by strong frequency dispersion and a rounded peak shape of gigantic dielectric susceptibility. The relaxor phase arises from one-dimensional ferroelectricity, as evidenced by a diffuse x-ray scattering, in which interchain ferroelectric coupling associated with neutral-ionic transition is interrupted by impurity-generated neutral microclusters.

Current-induced insulator-metal transition and pattern formation in an organic charge-transfer complex

Organic molecular Mott insulators, in which carriers are localized as a result of the electron correlation, showed nonlinear electric conduction upon application of a high electric field along the molecular stacking axis. The current-driven low-resistive state of potassium 7,7,8,8-tetracyanoquinodimethanane was stabilized down to 2 kelvin, where a metallic path was visible with a microscope. The current flow caused a stripe-like periodic phase-segregation into the carrier-rich and carrier-poor regions along the current path.

[High-dose cytosine arabinoside treatment of leukemia with special reference to the optimal number of doses].

A high dose of cytosine arabinoside (ara-C) was given to 51 patients during consolidation therapy or with refractory or relapsed acute leukemia. Ara-C was administered as a 3-hour infusion at a dose ranging from 2 to 3 g/m2 every 12 hours, diluted in 500 ml of 5% dextrose in water for 2 to 6 days. Complete remission was attained in 3 (25%) of 12 evaluable patients. Two with blast crisis of chronic myelogenous leukemia of these did not obtain complete remission. Death due to marrow aplasia occurred in five patients, and two of these had relatively good performance status and were given a dose of 3.0 g/m2 x 8 or 12 of ara-C. At a dose of 3.0 g/m2 x 6, the mean duration of granulocytes of less than 100/mm3 was 6.7 days. This duration seemed to be manageable myelosuppression. Therefore, 3.0 g/m2 x 6 was thought to be an adequate dose. Seizure occurred in one patient, and conjunctivitis was seen in another. In conclusion, from the manageable myelosuppression observed, administration of 3.0 g/m2 x 6 of ara-C seemed to be an adequate dose.

Combination of pipemidic acid, colistin sodium methanesulfonate and nystatin may be less effective than nystatin alone for prevention of infection during chemotherapy-induced granulocytopenia in acute leukemia.

Pipemidic acid (PPA) and colistin sodium methanesulfonate (CLM) may selectively suppress aerobic gram-negative bacilli. Twenty-nine patients with acute leukemia were randomized after each course of consolidation chemotherapy to receive a single agent of nystatin (NYS) (34 courses) versus a combination of NYS, PPA and CLM (36 courses). The duration of fever over 39 degrees C was longer with the three drug combination (4.6 +/- 5.1 days) than with NYS alone (1.8 +/- 1.8 days) (P less than 0.01). Four cases of pneumonia occurred and four patients including one having pneumonia died of infection with the three drug combination, while no pneumonia or death occurred with NYS alone (P = 0.06 and P = 0.06, respectively). The combination of NYS, PPA and CLM may be less effective than NYS alone for the prevention of infection in acute leukemia patients with chemotherapy-associated granulocytopenia.

[Cefmenoxime or piperacillin plus amikacin. A prospective randomized comparison of empiric antibiotic therapy of febrile granulocytopenic cancer patients].

Cefmenoxime plus amikacin was compared in a prospective randomized trial with our standard regimen of piperacillin plus amikacin as an empiric therapy for fever in patients with granulocytopenia. Initial profound granulocytopenia (fewer than 100/mm3 mature granulocytes) was present in approximately 45% of the patients in trial of both treatment groups. Of 53 microbiologically and clinically documented infections treated with piperacillin plus amikacin, 36 (68%) showed improvement. Of 48 microbiologically and clinically documented infections treated with cefmenoxime plus amikacin, 23 (48%) showed improvement. The response rate for gram-negative infections treated with cefmenoxime plus amikacin was lower than that for infections treated with piperacillin plus amikacin. Toxicity was minimal, with an equivalent incidence of skin rash, diarrhea and hepatic dysfunction. Although clinical efficacy of the combination of piperacillin plus amikacin may be superior to cefmenoxime plus amikacin therapy, this study demonstrated no statistically significant differences.

Differentiation of blasts from patients in myeloid crisis of chronic myelogenous leukemia by in-vivo and in-vitro plicamycin treatment.

Two cases in myeloid blast phase of chronic myelogenous leukemia (CML) responded to treatment with plicamycin alone. Their total white blood cell (WBC) count and immature myeloid cells fell in one case rapidly and in the other gradually. Approximately two to three weeks after initiation of plicamycin their total WBC count began to rise again, whereas the mature myeloid cells remained constant throughout the treatment. These results suggest that plicamycin may be effective in suppressing proliferation of blasts and promoting their maturation in the myeloid blast phase of CML, but that plicamycin alone may not be effective enough to sustain duration of response.