Antiferromagnetic Order and \pi-triplet Pairing in the Fulde-Ferrell-Larkin-Ovchinnikov State (2009)
Yanase, Youichi, Sigrist, Manfred
The antiferromagnetic Fulde-Ferrell-Larkin-Ovchinnikov (AFM-FFLO) state of coexisting d-wave FFLO superconductivity and incommensurate AFM order is studied on the basis of Bogoliubov-de Gennes (BdG)...
Disordered Fulde-Ferrel-Larkin-Ovchinnikov State in d-wave Superconductors (2009)
We study the Fulde-Ferrel-Larkin-Ovchinnikov (FFLO) superconducting state in the disordered systems. We analyze the microscopic model, in which the d-wave superconductivity is stabilized near the...
Localization and Superconductivity in Doped Semiconductors (2008)
Yanase, Youichi, Yorozu, Naoyuki
Motivated by the discovery of superconductivity in boron-doped (B-doped) diamond, we investigate the localization and superconductivity in heavily doped semiconductors. The competition between...
Antiferromagnetic order in the FFLO state (2008)
Yanase, Youichi, Sigrist, Manfred
We investigate the antiferromagnetic (AF) order in the d-wave superconducting (SC) state at high magnetic fields. A two-dimensional model with on-site repulsion U, inter-site attractive interaction V...
Superconductivity and Magnetism in Non-centrosymmetric System: Application to CePt_3Si (2008)
Yanase, Youichi, Sigrist, Manfred
Superconductivity and magnetism in the non-centrosymmetric heavy fermion compound CePt$_3$Si and related materials are theoretically investigated. Based on the randam phase approximation (RPA)...
FFLO Superconductivity near the Antiferromagnetic Quantum Critical Point (2008)
The Fulde-Ferrel-Larkin-Ovchinnikov (FFLO) state near the antiferromagnetic quantum critical point (AFQCP) is investigated by analyzing the two dimensional Hubbard model on the basis of the...
Yanase, Youichi, Sigrist, Manfred
The paramagnetic properties in non-centrosymmetric superconductors with and without antiferromagnetic (AFM) order are investigated with focus on the heavy Fermion superconductors, CePt_3Si, CeRhSi_3...
Yanase, Youichi, Sigrist, Manfred
The influence of antiferromagnetic order on the superconductivity in the non-centrosymmetric heavy fermion compound CePt$_3$Si and related materials is discussed. Based on our RPA analysis for the...
Superconducting Fluctuation and Pseudogap in Disordered Short Coherence Length Superconductor (2007)
We investigate the role of disorder on the superconducting (SC) fluctuation in short coherence length d-wave superconductors. The particular intetest is focused on the disorder-induced microscopic...
Formation of non-unitary state near the upper-critical field of Sr$_2$RuO$_4$ (2005)
Udagawa, Masafumi, Yanase, Youichi, Ogata, Masao
We have studied the superconducting state of Sr$_2$RuO$_4$ under a magnetic field parallel to the superconducting plane. We show that due to a weak spin-orbit coupling, non-unitary...
Yanase, Youichi, Mochizuki, Masahito, Ogata, Masao
The possibility of multiple phase diagram in the novel superconductor Na_{x}CoO_{2}yH_{2}O is analyzed on the basis of the multi-orbital Hubbard model including the atomic spin-orbit coupling. We...
Yanase, Youichi, Mochizuki, Masahito, Ogata, Masao
The d-vector in possibile spin triplet superconductor Na_{x}CoO_{2}yH_{2}O is microscopically investigated on the basis of the multi-orbital Hubbard model including the atomic spin-orbit coupling. As...
Mochizuki, Masahito, Yanase, Youichi, Ogata, Masao
In the recently discovered Co-oxide superconductor Na_xCoO_2*yH_2O, the edge-shared CoO6 octahedra are trigonally contracted along the c-axis in the CoO2-plane. We study how this CoO6 distortion...
Mochizuki, Masahito, Yanase, Youichi, Ogata, Masao
Spin and charge fluctuations and superconductivity in Na_0.35CoO_2*1.3H_2O are studied based on a multi-orbital Hubbard model. By applying the fluctuation exchange (FLEX) approximation, we show that...
The mechanism of high-Tc superconductivity is investigated with interests on the microscopic aspects of the condensation energy. The theoretical analysis is performed on the basis of the FLEX...
Udagawa, Masafumi, Yanase, Youichi, Ogata, Masao
We have studied the field-orientational dependence of zero-energy density of states (FODOS) for a series of systems with different Fermi surface and superconducting gap structures. Instead of...
The pseudogap phenomena induced by the SC fluctuation are investigated in details. We perform a calculation beyond the 1-loop approximation. The SC fluctuation is microscopically derived on the basis...
Multi-orbital analysis on the Superconductivity in Na_{x}CoO_{2} \cdot y H_{2}O (2004)
Yanase, Youichi, Mochizuki, Masahito, Ogata, Masao
We preform a multi-orbital analysis on the novel superconductivity in Na_{x}CoO_{2} \cdot yH_{2}O. We construct a three-orbital model which reproduces the band structure expected from the LDA...
Mochizuki, Masahito, Yanase, Youichi, Ogata, Masao
Spin and charge fluctuations and superconductivity in a recently discovered superconductor Na_xCoO_2*yH_2O are studied based on a multi-orbital Hubbard model. Tight-binding parameters are determined...
Influence of superconducting gap structure on the quasiparticle spectrum in the vortex state (2004)
Udagawa, Masafumi, Yanase, Youichi, Ogata, Masao
We study the vortex state of a layered superconductor with vertical line nodes on its Fermi surface when a magnetic field is applied in the ab-plane direction. We rotate the magnetic field within the...
Superconductivity in Na_xCoO_2yH_2O by charge fluctuation (2003)
Tanaka, Yasuhiro, Yanase, Youichi, Ogata, Masao
A new mechanism for superconductivity in the newly discovered Co-based oxide is proposed by using charge fluctuation. A single-band extended Hubbard model on the triangular lattice is studied within...
Microscopic Identification of the D-vector in Triplet Superconductor Sr_2RuO_4 (2003)
Triplet superconductivity in Sr_2RuO_4 is investigated with main interest on its internal degree of freedom. We perform a microscopic calculation to investigate how the chiral state d(k) = (k_x \pm...
Theory of Electric Transport in the Pseudogap State of High-Tc Cuprates (2001)
We theoretically investigate the electric transport in the pseudogap state of High-Tc cuprates. Starting from the repulsive Hubbard model, we perform the microscopic calculation to describe the...
Pseudogap Phenomena and Superconducting Fluctuations in Hubbard Model for High-Tc Cuprates (2001)
Yanase, Youichi, Yamada, Kosaku
The pseudogap phenomena in High-$T_{{\rm c}}$ cuprates are investigated on the basis of the Hubbard model which includes only the on-site repulsive interaction $U$. We consider the pairing scenario...
Theory on Superconducting Transition from Pseudogap State (2000)
Yanase, Youichi, Jujo, Takanobu, Yamada, Kosaku
The anomalous properties of High-$T_{{\rm c}}$ cuprates are investigated both in the normal state and in the superconducting state. In particular, we pay atte ntion to the pseudogap in the normal...
Effect of Magnetic field on the Pseudogap Phenomena in High-Tc Cuprates (2000)
Yanase, Youichi, Yamada, Kosaku
We theoretically investigate the effect of magnetic field on the pseudogap phenomena in High-Tc cuprates. The obtained results well explain the experimental results including their doping...
Yanase, Youichi, Yamada, Kosaku
In this paper we study the effects of the strong coupling superconductivity on the normal state electronic structure. We point out that the pseudogap phenomena in High-T_c cuprates are naturally...