Observation of orbital resonance Hall effect in (TMTSF)2ClO4

We report the observation of a Hall effect driven by orbital resonance in the quasi-1-dimensional (q1D) organic conductor (TMTSF)2ClO4. Although a conventional Hall effect is not expected in this class of materials due to their reduced dimensionality, we observed a prominent Hall response at certain orientations of the magnetic field B corresponding to lattice vectors of the constituent molecular chains, known as the magic angles (MAs). We show that this Hall effect can be understood as the response of conducting planes generated by an effective locking of the orbital motion of the charge carriers to the MA driven by an electron-trajectory resonance. This phenomenon supports a class of theories describing the rich behavior of MA phenomena in q1D materials based on altered dimensionality. Furthermore, we observed that the effective carrier density of the conducting planes is exponentially suppressed in large B, which indicates possible density wave formation.

Muscle development in the bamboo sole Heteromycteris japonicus with special reference to larval branchial levators

Muscle development in the bamboo sole Heteromycteris japonicus was investigated, focusing primarily on the cranial muscles, using an improved whole mount immunohistochemical staining method with potassium hydroxide, hydrogen peroxide and trypsin. Larvae of H. japonicus had branchial levators, but not all of them were retained in adults, a condition also seen in the Japanese flounder Paralichthys olivaceus. In particular, larval branchial levators II and III disappeared during development, while I and IV remained to become the levator internus I and levator posterior, which were well-defined muscles in adults. In place of the atrophied muscles, levatores externi and levator internus II developed and regulated the branchial arches. The results showed that the muscle composition in the dorsal branchial arches changed to the adult form before metamorphosis in H. japonicus, as seen in P. olivaceus, and this transformation may be common to all members of that group.

Kosterlitz-Thouless-type transition in a charge ordered state of the layered organic conductor α-(BEDT-TTF)2I3

The current-voltage characteristics in the charge order state of the two-dimensional organic conductor α-(BEDT-TTF)(2)I(3) exhibit power law behavior at low temperatures. The power law is understood in terms of the electric-field-dependent potential between electrons and holes, which are thermally excited from the charge order state. The power law exponent steeply changes from 1 to 3 in the range from 30 to 45 K with decreasing temperature, thereby suggesting the occurrence of a Kosterlitz-Thouless-type transition; many (few) unbound electron-hole pairs are thermally excited above (below) the transition. The effects of the finite size and interlayer coupling on the power law behavior are discussed.

Novel Pauli-paramagnetic quantum phase in a Mott insulator

In Mott insulators, the strong electron-electron Coulomb repulsion localizes electrons. In dimensions greater than one, their spins are usually ordered antiferromagnetically at low temperatures. Geometrical frustrations can destroy this long-range order, leading to exotic quantum spin liquid states. However, their magnetic ground states have been a long-standing mystery. Here we show that a quantum spin liquid state in the organic Mott insulator EtMe(3)Sb[Pd(dmit)(2)](2) (where Et is C(2)H(5)-, Me is CH(3)-, and dmit is 1,3-dithiole-2-thione-4,5-dithiolate) with two-dimensional triangular lattice has Pauli-paramagnetic-like low-energy excitations, which are a hallmark of itinerant fermions. Our torque magnetometry down to low temperatures (30 mK) up to high fields (32 T) reveals distinct residual paramagnetic susceptibility comparable to that in a half-filled two-dimensional metal, demonstrating the magnetically gapless nature of the ground state. Moreover, our results are robust against deuteration, pointing toward the emergence of an extended 'quantum critical phase', in which low-energy spin excitations behave as in paramagnetic metals with Fermi surface, despite the frozen charge degree of freedom.

Density-of-state oscillation of quasiparticle excitation in the spin density wave phase of (TMTSF)2ClO4

Systematic measurements of the magnetocaloric effect, heat capacity, and magnetic torque under a high magnetic field up to 35 T are performed in the spin density wave (SDW) phase of a quasi-one-dimensional organic conductor (TMTSF)2ClO4. In the SDW phase above 26 T, where the quantum Hall effect is broken, rapid oscillations (ROs) in these thermodynamic quantities are observed, which provides clear evidence of the density-of-state (DOS) oscillation near the Fermi level. The resistance is semiconducting and the heat capacity divided by temperature is extrapolated to zero at 0 K in the SDW phase, showing that all the energy bands are gapped, and there is no DOS at the Fermi level. The results show that the ROs are ascribed to the DOS oscillation of the quasiparticle excitation.

Quasi-two-dimensional Fermi surfaces and coherent interlayer transport in KFe₂As₂

We report the results of the angular-dependent magnetoresistance oscillations (AMROs), which can determine the shape of bulk Fermi surfaces (FSs) in quasi-two-dimensional (Q2D) systems, in a highly hole-doped Fe-based superconductor KFe2As2 with Tc ≈ 3.7  K. From the AMROs, we determined the two Q2D FSs with rounded-square cross sections, correspond to 12% and 17% of the first Brillouin zone. The rounded-squared shape of the FS cross section is also confirmed by the analyses of the interlayer transport under in-plane fields. From the obtained FS shape, we infer the character of the 3d orbitals that contribute to the FSs.

Fermi surface properties of CeRu2(Si1-xGex)2 in magnetic fields above the metamagnetic transitions

We report de Haas-van Alphen effect measurements on CeRu2(Si(1-x)Gex)2 to reveal electronic structure change over the broad range of chemical pressure from x=0.0 to 1.0. It is found that the Fermi surface properties change drastically across the metamagnetic crossover field (B(m)) but vary smoothly with x from those in magnetic fields above B(m) in CeRu2Si2 to those in the ferromagnetic state in CeRu2Ge2. Implications of the present results are discussed in conjunction with the magnetic phase diagram.

Extremely high upper critical magnetic field of the noncentrosymmetric heavy fermion superconductor CeRhSi3

We report an extremely high upper critical field B(c2) in the noncentrosymmetric heavy fermion superconductor CeRhSi3 for a magnetic field B along the tetragonal c axis. B(c2)(T=0) possibly reaching 30 T is much higher than B(c2)(0)=7 T for B perpendicular c and greatly exceeds the paramagnetic limiting field. The strong anisotropy of B(c2)(0) with extremely high B(c2)(0) for B || c is qualitatively explained by the paramagnetic pair-breaking mechanism specific to the noncentrosymmetric superconductor. However, an unusual B(c2)(T) curve with a positive curvature for B || c cannot be explained satisfactorily by conventional orbital pair-breaking models.

Vortex dynamics and the Fulde-Ferrell-Larkin-Ovchinnikov state in a magnetic-field-induced organic superconductor

Under special conditions, a superconducting state where the order parameter oscillates in real space, the so-called FFLO state, is theoretically predicted to exist near the upper critical field, as first proposed by Fulde and Ferrell, and Larkin and Ovchinnikov. We report systematic measurements of the interlayer resistance in high magnetic fields to 45 T in the two-dimensional magnetic-field-induced organic superconductor lambda-(BETS)2FeCl4, where BETS is bis(ethylenedithio)tetraselenafulvalene. The resistance is found to show characteristic dip structures in the superconducting state. The results are consistent with pinning interactions between the vortices penetrating the insulating layers and the order parameter of the FFLO state. This gives strong evidence for an oscillating order parameter in real space.

Quantum oscillation of Hall resistance in the extreme quantum limit of an organic conductor (TMTSF)2ClO4

We report resistance and magnetic torque experiments under a high magnetic field up to 45 T in a three dimensional quantum Hall (QH) system (TMTSF)(2)ClO(4), where TMTSF = tetramethyltetraselenafulvalene. The Hall resistance shows huge oscillations accompanied with sign reversal after the final QH state, where the Landau level filling factor is unity, is removed above 26 T. The magnetic torque also oscillates with the field. The results suggest that a novel quantum state, where the character of the carriers periodically changes with the field, is stabilized in the extreme quantum limit.

Evolution of spin and field dependences of the effective mass with pressure in CeIn(3)

We have studied the field and spin dependences of the effective masses in CeIn3 as a function of pressure via the de Haas-van Alphen (dHvA) effect. The effective mass increases with the field at pressures up to about 10 kbar and then decreases with the field. The spin direction of the dominant dHvA oscillation is likely to be reversed across the same pressure. The dHvA frequency changes significantly at the pressure P(c) for the antiferromagnetic quantum critical point and two neighboring pressures P2 and P4 below and above P(c). The spin and field dependences rapidly diminish across P(c) and finally disappear above P4. These observations are discussed in conjunction with relevant observations and theories.

de Haas-van Alphen effect in ZrZn2 under pressure: crossover between two magnetic states

We report measurements of the de Haas-van Alphen effect in ZrZn2 under hydrostatic pressures up to 21 kbar where the Curie temperature vanishes. The exchange splitting of a Fermi surface changes in behavior with increasing magnetic field, which is qualitatively consistent with the behavior of the high-field magnetization, suggesting the existence of a crossover between two distinct magnetic states. These and previously unexplained findings may be understood in terms of a p-T-B phase diagram qualitatively similar to that of the ferromagnetic superconductor UGe2.

Dependence of the effective masses in YbAl3 on magnetic field and disorder

The susceptibility and specific heat--and hence the effective mass--of the intermediate valence compound YbAl3 show anomalous enhancement below the Fermi liquid temperature T(coh) approximately 40 K. We show that these anomalies are suppressed by alloying in Yb1-xLuxAl3 indicating high sensitivity to lattice coherence. The de Haas-van Alphen effective masses for key branches of the Fermi surface are reduced by magnetic fields B>40 T. We argue that this reduction does not arise from 4f polarization but reflects renormalization of the quasiparticle states by the field.

Evolution of quasiparticle properties in UGe(2) with hydrostatic pressure studied via the de Haas-van Alphen effect

We report measurements of the de Haas-van Alphen effect in UGe (2) under hydrostatic pressures up to 17.6 kbar, exceeding the critical pressure P(c) for the suppression of ferromagnetism. A discontinuous change of the Fermi surface is found to occur across P(c). Substantially enhanced effective masses (approximately 40m(e)) are found near P(c) on both the ferromagnetic and the paramagnetic sides.

Superconductivity in an organic insulator at very high magnetic fields

We investigate by electrical transport the field-induced superconducting state (FISC) in the organic conductor lambda-(BETS)2FeCl4. Below 4 K, antiferromagnetic-insulator, metallic, and eventually superconducting (FISC) ground states are observed with increasing in-plane magnetic field. The FISC state survives between 18 and 41 T and can be interpreted in terms of the Jaccarino-Peter effect, where the external magnetic field compensates the exchange field of aligned Fe3+ ions. We further argue that the Fe3+ moments are essential to stabilize the resulting singlet, two-dimensional superconducting state.

Magnetic-field-induced superconductivity in a two-dimensional organic conductor

The application of a sufficiently strong magnetic field to a superconductor will, in general, destroy the superconducting state. Two mechanisms are responsible for this. The first is the Zeeman effect, which breaks apart the paired electrons if they are in a spin-singlet (but not a spin-triplet) state. The second is the so-called 'orbital' effect, whereby the vortices penetrate into the superconductors and the energy gain due to the formation of the paired electrons is lost. For the case of layered, two-dimensional superconductors, such as the high-Tc copper oxides, the orbital effect is reduced when the applied magnetic field is parallel to the conducting layers. Here we report resistance and magnetic-torque experiments on single crystals of the quasi-two-dimensional organic conductor lambda-(BETS)2FeCl4, where BETS is bis(ethylenedithio)tetraselenafulvalene. We find that for magnetic fields applied exactly parallel to the conducting layers of the crystals, superconductivity is induced for fields above 17 T at a temperature of 0.1 K. The resulting phase diagram indicates that the transition temperature increases with magnetic field, that is, the superconducting state is further stabilized with magnetic field.

[A surgical case of cor triatriatum complicated by arterial multiple embolism in adult]

A 30 year old male developed sudden chest pain while driving his car and was subsequently admitted to our hospital. Cardiac catheterization and arteriography revealed multiple embolism in the right coronary artery, the right renal artery and the both popliteal arteries. Thrombus was also suspected in the left atrium by echocardiography. Emergent surgery was performed to prevent recurrence of embolism, IA type cor triatriatum (according to the Lucus-Schmidt classification) and 3 x 1 cm thrombus in the accessory chamber was found. The thrombus was extracted and the abnormal septum was satisfactorily resected. The postoperative course was favourable and the patient returned to the community after discharge. Cases of cor triatriatum complicated by multiple arterial embolism are very rare and have not been reported in Japan yet. For this reason we present this case with additional discussion from literature.

[A surgical case of left coronary artery-left ventricular fistula]

Left ventricular fistulas arising from the left coronary artery are rare, and only 3 cases have been reported Japan. Surgical closure of a left coronary artery-left ventricular fistula in a 14-year old male was reported. The fistula was identified by coronary arteriography after the patient had been admitted to hospital complaining of recurrent chest pain. Ligation of the fistula involving the left anterior descending coronary artery was performed with cardiopulmonary bypass, chemical arrest and hypothermia. The blood flow through the LAD decreased from 370 ml/min to 100 ml/min after the fistula was ligated, and there was uneventful postoperative recovery. Furthermore chest pain of the patient was shown to diminish and movement of the left ventricular septum was improved, compared with the preoperative cineangiography. However, trivial residual flow fo the circumflex coronary artery to the left ventricle remained on postoperative coronary arteriography. The principal aim of the procedure for surgical correction should be effective closure of the fistula without compromising the distal blood supply of the coronary artery involved, cardiopulmonary bypass is considered necessary to appropriate closure of the fistula.

[A case of right intermediate bronchial stenosis due to an injury eighteen years before]

A 20 year-old man was admitted to our hospital suffering from fever and cough due to bronchiectasis. He had been injured in automobile accident 18 years before. The subsequent bronchography revealed a marked stricture of the right intermediate bronchus with post-stenotic bronchiectasis. Right middle and lower lobectomy was performed. Postoperatively, pneumonia improved, and pulmonary function was preserved. There is no agreement on criteria indicating the need for bronchial reconstruction in cases like this, because evaluation is difficult whether inflammatory changes in the lobes intending to the reimplant may be reversible. In our case, we considered that recurrent pneumonia and bronchiectatic changes of the right lower lobe were contra-indications to bronchial reconstruction.