arXiv subjects

H. Taniguchi

Publications and source records attributed to H. Taniguchi.

22 records · Page 2Linked to original sources

arXiv2013

Relaxor ferroelectricity induced by electron correlations in a molecular dimer Mott insulator

We have investigated the dielectric response in an antiferromagnetic dimer-Mott insulator beta'-(BEDT-TTF)2ICl2 with square lattice, compared to a spin liquid candidate kappa-(BEDT-TTF)2Cu2(CN)3. Temperature dependence of the dielectric constant shows a peak structure obeying Curie-Weiss law with strong frequency dependence. We found an anisotropic ferroelectricity by pyrocurrent measurements, which suggests the charge disproportionation in a dimer. The ferroelectric actual charge freezing temperature is related to the antiferromagnetic interaction, which is expected to the charge-spin coupled degrees of freedom in the system.

cond-mat.str-el↗

arXiv2005

The origin of the phase separation in partially deuterated $κ$-(ET)$_2$Cu[N(CN)$_2$]Br studied by infrared magneto-optical imaging spectroscopy

The direct observation of the phase separation between the metallic and insulating states of 75 %-deuterated $κ$-(ET)$_2$Cu[N(CN)$_2$]Br ($d33$) using infrared magneto-optical imaging spectroscopy is reported, as well as the associated temperature, cooling rate, and magnetic field dependencies of the separation. The distribution of the center of spectral weight ($< ω>$) of $d33$ did not change under any of the conditions in which data were taken and was wider than that of the non-deuterated material. This result indicates that the inhomogenity of the sample itself is important as part of the origin of the metal - insulator phase separation.

cond-mat.str-el↗

arXiv2003

Influence of the cooling rate on low-temperature Raman and infrared reflection spectra of partially deuterated k-(BEDT-TTF)_2Cu[N(CN)_2]Br

Raman and IR spectra of k-(BEDT-TTF)_2Cu[N(CN)_2]Br [BEDT-TTF denotes bis(ethylenedithiolo)tetrathiafulvalene] and its deuterated and partially deuterated analogues were measured at temperatures between 5 and 300 K and cooling rates from 1 to 20 K/min. It was found that, in partially deuterated samples, the interdimer electron-molecular vibration splitting of nu_3 mode in Raman spectra, the magnitude of the resonance enhancement in Raman spectra, and linewidths of some phonon peaks both in Raman and infrared spectra depend on the cooling rate. These observations were explained by disorder-related effects.

cond-mat.supr-con↗

arXiv2001

The C=C Stretching Vibrations of k-(BEDT-TTF)_2Cu[N(CN)_2]Br and Its Isotope Analogues

The C=C stretching modes in resonance Raman spectra and infrared reflectivity were measured at temperatures between 15 K and 300 K using various polarizations in k-(BEDT-TTF)_2Cu[N(CN)_2]Br, its fully and partially deuterated analogues, and ^{13}C-substituted analogue. The infrared- and Raman-active bands were re-assigned based on the factor group analysis. We found a Raman-active EMV-coupled ν_3 mode near 1420 cm_{-1}, which shows a large downshift and broadening through the inter-dimer EMV interaction. The mixing of the bridge and ring C=C stretching vibrations depends upon the symmetry of the crystal mode. In contrast to deuterated crystals, the non-deuterated crystals show a splitting in the ν_2, ν_3, and ν_{27} bands.

cond-mat.supr-con↗