Hiroshi Yamamoto | The University of Tokyo (original) (raw)
Uploads
Papers by Hiroshi Yamamoto
Nature communications, Jan 5, 2016
It is widely recognized that the effect of doping into a Mott insulator is complicated and unpred... more It is widely recognized that the effect of doping into a Mott insulator is complicated and unpredictable, as can be seen by examining the Hall coefficient in high Tc cuprates. The doping effect, including the electron-hole doping asymmetry, may be more straightforward in doped organic Mott insulators owing to their simple electronic structures. Here we investigate the doping asymmetry of an organic Mott insulator by carrying out electric-double-layer transistor measurements and using cluster perturbation theory. The calculations predict that strongly anisotropic suppression of the spectral weight results in the Fermi arc state under hole doping, while a relatively uniform spectral weight results in the emergence of a non-interacting-like Fermi surface (FS) in the electron-doped state. In accordance with the calculations, the experimentally observed Hall coefficients and resistivity anisotropy correspond to the pocket formed by the Fermi arcs under hole doping and to the non-interact...
Nature Communications, 2013
In state-of-the-art silicon devices, mobility of the carrier is enhanced by the lattice strain fr... more In state-of-the-art silicon devices, mobility of the carrier is enhanced by the lattice strain from the back substrate. Such an extra control of device performance is significant in realizing high performance computing and should be valid for electric-field-induced superconducting devices, too. However, so far, the carrier density is the sole parameter for field-induced superconducting interfaces. Here we show an active organic superconducting field-effect-transistor whose lattice is modulated by the strain from the substrate. The soft organic lattice allows tuning of the strain by a choice of the back substrate to make an induced superconducting state accessible at low temperature with a paraelectric solid gate. An active three terminal Josephson junction device thus realized is useful both in advanced computing and in elucidating a direct connection between filling-controlled and bandwidth-controlled superconducting phases in correlated materials.
Journal of Materials Chemistry, 2001
Cl(pBIB) (ET~bis(ethylenedithio)tetrathiafulvalene, pBIB~p-bis(iodoethynyl)benzene) salt is a uni... more Cl(pBIB) (ET~bis(ethylenedithio)tetrathiafulvalene, pBIB~p-bis(iodoethynyl)benzene) salt is a unique organic metal containing supramolecular assemblies based on the pBIB molecule and the Cl anion. We newly prepared chloride and bromide ET cation radical salts with the use of di-and tetra-substituted pBIB derivatives: 1,4-difluoro-2,5-bis(iodoethynyl)benzene (DFBIB), 1,2,4,5-tetrafluoro-3,6-bis(iodoethynyl)benzene (TFBIB), 1,4-bis(iodoethynyl)-2,5-dimethylbenzene (BIDMB), and p-bis(iodoethynyl)benzene-d 4 (pBIB-d 4). The effect of substitution has been studied by X-ray structure analyses, tight-binding band calculations, and resistivity measurements. Halide ion replacement as well as deuterium-and difluoro-substitutions do not change the fundamental crystal structure and the metallic behavior, but affect the anisotropy of the electronic structure. On the other hand, the tetrafluoro-and dimethyl-substitutions induce different donor arrangements that lead to semiconducting behaviors.
Journal of Materials Chemistry, 1998
Materials Communication Structural and electrical properties of (BEDT-TTF) 2 X(diiodoacetylene) (... more Materials Communication Structural and electrical properties of (BEDT-TTF) 2 X(diiodoacetylene) (X=Cl, Br): the novel self-assembly of neutral Lewis-acidic molecules and halide anions in a molecular metal
Journal of the …, 2006
Multiprobe measurements were performed on tiny single crystals of DMe-DCNQI complexes prepared di... more Multiprobe measurements were performed on tiny single crystals of DMe-DCNQI complexes prepared directly on SiO2/Si substrates. The differences in conduction properties between the micro-and nanocrystals and bulk crystals were observed.
Nature communications, Jan 5, 2016
It is widely recognized that the effect of doping into a Mott insulator is complicated and unpred... more It is widely recognized that the effect of doping into a Mott insulator is complicated and unpredictable, as can be seen by examining the Hall coefficient in high Tc cuprates. The doping effect, including the electron-hole doping asymmetry, may be more straightforward in doped organic Mott insulators owing to their simple electronic structures. Here we investigate the doping asymmetry of an organic Mott insulator by carrying out electric-double-layer transistor measurements and using cluster perturbation theory. The calculations predict that strongly anisotropic suppression of the spectral weight results in the Fermi arc state under hole doping, while a relatively uniform spectral weight results in the emergence of a non-interacting-like Fermi surface (FS) in the electron-doped state. In accordance with the calculations, the experimentally observed Hall coefficients and resistivity anisotropy correspond to the pocket formed by the Fermi arcs under hole doping and to the non-interact...
Nature Communications, 2013
In state-of-the-art silicon devices, mobility of the carrier is enhanced by the lattice strain fr... more In state-of-the-art silicon devices, mobility of the carrier is enhanced by the lattice strain from the back substrate. Such an extra control of device performance is significant in realizing high performance computing and should be valid for electric-field-induced superconducting devices, too. However, so far, the carrier density is the sole parameter for field-induced superconducting interfaces. Here we show an active organic superconducting field-effect-transistor whose lattice is modulated by the strain from the substrate. The soft organic lattice allows tuning of the strain by a choice of the back substrate to make an induced superconducting state accessible at low temperature with a paraelectric solid gate. An active three terminal Josephson junction device thus realized is useful both in advanced computing and in elucidating a direct connection between filling-controlled and bandwidth-controlled superconducting phases in correlated materials.
Journal of Materials Chemistry, 2001
Cl(pBIB) (ET~bis(ethylenedithio)tetrathiafulvalene, pBIB~p-bis(iodoethynyl)benzene) salt is a uni... more Cl(pBIB) (ET~bis(ethylenedithio)tetrathiafulvalene, pBIB~p-bis(iodoethynyl)benzene) salt is a unique organic metal containing supramolecular assemblies based on the pBIB molecule and the Cl anion. We newly prepared chloride and bromide ET cation radical salts with the use of di-and tetra-substituted pBIB derivatives: 1,4-difluoro-2,5-bis(iodoethynyl)benzene (DFBIB), 1,2,4,5-tetrafluoro-3,6-bis(iodoethynyl)benzene (TFBIB), 1,4-bis(iodoethynyl)-2,5-dimethylbenzene (BIDMB), and p-bis(iodoethynyl)benzene-d 4 (pBIB-d 4). The effect of substitution has been studied by X-ray structure analyses, tight-binding band calculations, and resistivity measurements. Halide ion replacement as well as deuterium-and difluoro-substitutions do not change the fundamental crystal structure and the metallic behavior, but affect the anisotropy of the electronic structure. On the other hand, the tetrafluoro-and dimethyl-substitutions induce different donor arrangements that lead to semiconducting behaviors.
Journal of Materials Chemistry, 1998
Materials Communication Structural and electrical properties of (BEDT-TTF) 2 X(diiodoacetylene) (... more Materials Communication Structural and electrical properties of (BEDT-TTF) 2 X(diiodoacetylene) (X=Cl, Br): the novel self-assembly of neutral Lewis-acidic molecules and halide anions in a molecular metal
Journal of the …, 2006
Multiprobe measurements were performed on tiny single crystals of DMe-DCNQI complexes prepared di... more Multiprobe measurements were performed on tiny single crystals of DMe-DCNQI complexes prepared directly on SiO2/Si substrates. The differences in conduction properties between the micro-and nanocrystals and bulk crystals were observed.