arXiv subjects

H. Mori

Publications and source records attributed to H. Mori.

24 records · Page 2Linked to original sources

arXiv2002

Infrared properties of $θ$-type ET charge-transfer salts: $θ$-ET$_2$CsZn(SCN)$_4$ vs $θ$-ET$_2$RbZn(SCN)$_4$

We performed polarized far-infrared reflectance measurements at different temperatures on $θ$-ET$_2$RbZn(SCN)$_4$ and $θ$-ET$_2$CsZn(SCN)$_4$, two typical charge-transfer salts in a series of isostructural $θ$-ET$_2$MM'(SCN)$_4$. The measurements revealed distinct differences in both electronic and vibronic spectra, which provides a clue towards understanding the different metal-insulator transitions of the two salts.

cond-mat.str-el↗

arXiv2002

Crystal growth and characterization of MgB2: Relation between structure and superconducting properties

We discuss the important aspects of synthesis and crystal growth of MgB2 under high pressure (P) and temperature (T) in Mg-B-N system, including the optimisation of P-T conditions for reproducible crystal growth, the role of liquid phases in this process, the temperature dependence of crystal size and the effect of growing instabilities on single crystals morphology. Extensive experiments have been carried out on single crystals with slightly different lattice constants and defects concentration, which revealed and possible effects of Mg-deficiency and lattice strain on the superconducting properties of MgB2 (Tc, Jc, residual resistivity ratio, anisotropy etc.).

cond-mat.supr-con↗

arXiv2001

Growth, structure analysis and anisotropic superconducting properties of MgB2 single crystals

Here we report the growth of sub-millimeter MgB2 single crystals of various shapes under high pressure in Mg-B-N system. Structure refinement using a single-crystal X-ray diffraction analysis gives lattice parameters a=3.0851(5) A and c=3.5201(5) A with small reliability factors (Rw =0.025, R=0.018), which enables us to analyze the Fourier and Fourier difference maps. The maps clearly show the B sp2 orbitals and covalency of the B-B bonds. The sharp superconducting transitions at Tc =38.1-38.3K were obtained in both magnetization (DTc =0.6K) and resistivity (DTc <0.3K) measurements. Resistivity measurements with magnetic fields applied parallel and perpendicular to the Mg and B sheets reveal the anisotropic nature of this compound, with upper critical field anisotropy ratio of about 2.7.

cond-mat.supr-con↗

arXiv2001

Far-infrared study of the insulator-metal transition in $θ$-(BEDT-TTF)$_2$RbZn(SCN)$_4$

The temperature-dependent infrared properties of $θ$-(BEDT-TTF)$_2$RbZn(SCN)$_4$ were investigated. In the temperatures above the metal-insulator (M-I) transition, the optical conductivity remains finite in the low energy region, but shows no conventional Drude feature typical of metals. Below the M-I transition temperature, the low-energy spectral weight is significantly reduced. An opening of optical gap at about 300 cm$^{-1}$ is observed clearly in the polarization parallel to the donor-stacking direction. Analysis of both the electronic and vibronic spectra suggests a redistribution of charges in ET molecules as temperature decreases across the M-I transition, providing strong support for the charge-ordering state at low temperatures.

cond-mat.str-el↗

arXiv1996

Spontaneous Interlayer Coherence in Double-Layer Quantum Hall Systems: Symmetry Breaking Interactions, In-Plane Fields and Phase Solitons

At strong magnetic fields double-layer two-dimensional-electron-gas systems can form an unusual broken symmetry state with spontaneous inter-layer phase coherence. The system can be mapped to an equivalent system of pseudospin $1/2$ particles with pseudospin-dependent interactions and easy-plane magnetic order. In this paper we discuss how the presence of a weak interlayer tunneling term alters the properties of double-layer systems when the broken symmetry is present. We use the energy functional and equations of motion derived earlier to evaluate the zero-temperature response functions of the double-layer system and use our results to discuss analogies between this system and Josephson-coupled superconducting films. We also present a qualitative picture of the low-energy charged excitations of this system. We show that parallel fields induce a highly collective phase transition to an incommensurate state with broken translational symmetry.

cond-mat↗

arXiv1994

Spontaneous Inter-layer Coherence in Double-Layer Quantum-Hall Systems I: Charged Vortices and Kosterlitz-Thouless Phase Transitions

At strong magnetic fields double-layer two-dimensional-electron-gas systems can form an unusual broken symmetry state with spontaneous inter-layer phase coherence. In this paper we explore the rich variety of quantum and finite-temperature phase transitions associated with this broken symmetry. We describe the system using a pseudospin language in which the layer degree-of-freedom is mapped to a fictional spin 1/2 degree-of-freedom. With this mapping the spontaneous symmetry breaking is equivalent to that of a spin 1/2 easy-plane ferromagnet. In this language spin-textures can carry a charge. In particular, vortices carry e/2 electrical charge and vortex-antivortex pairs can be neutral or carry charge e. We derive an effective low-energy action and use it to discuss the charged and collective neutral excitations of the system. We have obtained the parameters of the Landau-Ginzburg functional from first-principles estimates and from finite-size exact diagonalization studies. We use these results to estimate the dependence of the critical temperature for the Kosterlitz-Thouless phase transition on layer separation.

cond-mat↗