T. Nishi

New Infrared and Terahertz Beam Line BL6B at UVSOR

We have designed a new infrared beam line BL6B at UVSOR for infrared and terahertz spectroscopies including microspectroscopy with high brilliance and high flux. The beam line will be replaced in the spring of 2004 from the infrared beam line, BL6A1, at UVSOR. The beam line has a large acceptance angle of 215(H) × 80(V) mrad2 and a so‐called “magic mirror” is adopted to get the perfect focusing of the bending magnet radiation. The optics and expected performance (focus size, photon flux and brilliance) are reported.

Magnetic-field-induced superconductor-insulator-metal transition in an organic conductor : An infrared magneto-optical imaging spectroscopic study

The magnetic-field-induced superconductor-insulator-metal transition (SIMT) in partially deuterated

Pressure dependence of the phase separation in deuterated κ-(BEDT-TTF)2Cu[N(CN)2]Br at the Mott boundary

\ensuremath{\kappa}\text{\ensuremath{-}}{(\mathrm{BEDT}\text{\ensuremath{-}}\mathrm{TTF})}_{2}\mathrm{Cu}[\mathrm{N}{(\mathrm{C}\mathrm{N})}_{2}]\mathrm{Br}

Infrared spectroscopy under multiextreme conditions : Direct observation of pseudogap formation and collapse in CeSb

, which is just on the Mott boundary, has been observed using the infrared magneto-optical imaging spectroscopy. The infrared reflectivity image on the sample surface revealed that the metallic (or superconducting) and insulating phases coexist and they have different magnetic-field dependences. One of the magnetic-field dependence is SIMT that appeared on part of the sample surface. The SIMT was concluded to originate from the balance of the inhomogeneity in the sample itself and the disorder of the ethylene end groups resulting from fast cooling.

Infrared spectroscopy under extreme conditions

The pressure dependence of the optical reflectivity spectrum [R(ω)R(ω)] of deuterated κ-(BEDT-TTF)2Cu[N(CN)2]Br(d44)κ-(BEDT-TTF)2Cu[N(CN)2]Br(d44) at T=4.5K was determined. At the ambient pressure, d44d44 under fast cooling conditions forms an antiferromagnetic insulator (AFI) phase, as confirmed by the wavenumber of the ν3(ag)ν3(ag) vibration mode. At the pressures in the range of several MPa, the optical spectrum changes to that of a metal that matches a non-deuterated material consisting of AFI and PM (paramagnetic metallic) spectra. This indicates that the phase separation between the AFI and PM phases appears at intermediate pressures. The phase size of the separated phase is smaller than the instrumental spatial resolution of 50μm, based on the inability of our methods to record it.

Pressure dependence of the phase separation in deuterated κ-(BEDT-TTF)2Cu[N(CN)2]Brκ-(BEDT-TTF)2Cu[N(CN)2]Br at the Mott boundary

Infrared reflectivity measurements of CeSb under multi-extreme conditions (low temperatures, high pressures and high magnetic fields) were performed. A pseudo gap structure, which originates from the magnetic band folding effect, responsible for the large enhancement in the electrical resistivity in the single-layered antiferromagnetic structure (AF-1 phase) was found at a pressure of 4 GPa and at temperatures of 35 - 50 K. The optical spectrum of the pseudo gap changes to that of a metallic structure with increasing magnetic field strength and increasing temperature. This change is the result of the magnetic phase transition from the AF-1 phase to other phases as a function of the magnetic field strength and temperature. This result is the first optical observation of the formation and collapse of a pseudo gap under multi-extreme conditions.

Pressure dependence of the phase separation in deuterated at the Mott boundary

Abstract We constructed a magneto-optical microspectroscopy apparatus in the infrared region using a synchrotron radiation, SPring-8. In the apparatus, an infrared microscope with the spatial resolution of ∼11 μm is combined with low temperatures (⩾3.5 K ) and high magnetic fields (⩽14 T ) . The purpose is to investigate the electronic structure under extreme conditions of tiny materials such as organic conductors and of small region and the spatial distribution of electronic structures. After the installation of high pressure cells, optical measurements under multiple-extreme conditions is available. The specification of the apparatus and recent results of an organic superconductor are presented.

Infrared and terahertz spectromicroscopy beam line BL6B(IR) at UVSOR-II

The pressure dependence of the optical reflectivity spectrum [R(ω)R(ω)] of deuterated κ-(BEDT-TTF)2Cu[N(CN)2]Br(d44)κ-(BEDT-TTF)2Cu[N(CN)2]Br(d44) at T=4.5K was determined. At the ambient pressure, d44d44 under fast cooling conditions forms an antiferromagnetic insulator (AFI) phase, as confirmed by the wavenumber of the ν3(ag)ν3(ag) vibration mode. At the pressures in the range of several MPa, the optical spectrum changes to that of a metal that matches a non-deuterated material consisting of AFI and PM (paramagnetic metallic) spectra. This indicates that the phase separation between the AFI and PM phases appears at intermediate pressures. The phase size of the separated phase is smaller than the instrumental spatial resolution of 50μm, based on the inability of our methods to record it.

The origin of the phase separation in partially deuterated κ-(ET)2Cu[N(CN)2]Br studied by infrared magneto-optical imaging spectroscopy

The pressure dependence of the optical reflectivity spectrum [R(ω)R(ω)] of deuterated κ-(BEDT-TTF)2Cu[N(CN)2]Br(d44)κ-(BEDT-TTF)2Cu[N(CN)2]Br(d44) at T=4.5K was determined. At the ambient pressure, d44d44 under fast cooling conditions forms an antiferromagnetic insulator (AFI) phase, as confirmed by the wavenumber of the ν3(ag)ν3(ag) vibration mode. At the pressures in the range of several MPa, the optical spectrum changes to that of a metal that matches a non-deuterated material consisting of AFI and PM (paramagnetic metallic) spectra. This indicates that the phase separation between the AFI and PM phases appears at intermediate pressures. The phase size of the separated phase is smaller than the instrumental spatial resolution of 50μm, based on the inability of our methods to record it.