Related papers: Fermi liquid behavior and spin-charge separation i…
We study the doping dependence of low frequency spin fluctuations and the zero-temperature superfluid density of La$_{2-x}$Sr$_x$CuO$_4$ using the muon spin relaxation ($\mu$SR) and ac-susceptibility techniques. Superconductivity is found…
The thermodynamics of the superconducting transition is studied as a function of doping using high-resolution expansivity data of YBa2Cu3Ox single crystals and Monte-Carlo simulations of the anisotropic 3D-XY model. We directly show that Tc…
We have been able to resolve two long-standing issues that are central to the theory of high Tc superconductivity: (1) How is the physics of the doped region connected to that of the Mott insulator? (2) What is the origin of the…
We study Cooper-pair phase fluctuations in cuprate superconductors for a spin fluctuation pairing interaction. Using an electronic theory we calculate in particular for the underdoped cuprate superconductors the superfluid density $n_s(T)$,…
We evaluate the frequencies of scissors modes for density and concentration fluctuations in a vapour of fermionic atoms placed in two hyperfine levels inside a spherical harmonic trap. Both the superfluid and the normal state are…
The studies of high-temperature superconductors raise a fundamental question: Can a small Fermi surface phase, which violates the Luttinger theorem, exist and give rise to superconductivity? Our work provides a positive answer through a…
In high-temperature cuprate superconductors, the anti-ferromagnetic spin fluctuations are thought to have a very important role in naturally producing an attractive interaction between the electrons in the $d$-wave channel. The connection…
We investigate the supercurrent through a quantum dot for the whole range of couplings using the numerical renormalization group method. We find that the Josephson current switches abruptly from a $\pi$- to a 0-phase as the coupling…
As is known, the 1/q^2 theorem of Bogoliubov asserts that the mean density of the fermion pair states with the total momentum q obeys the inequality n_q > C/q^2 (q \to 0) in the case of the Fermi system taken at nonzero temperature and in…
In the presence of nonlocal phase shift effects, a quasiparticle can remain topologically stable even in a spin-charge separation state due to the confinement effect introduced by the phase shifts at finite doping. True deconfinement only…
The phenomenon of field-induced superconductor-to-insulator transitions observed experimentally in electron-doped SrTiO$_{3}$/LaAlO$_{3}$ interfaces, analyzed recently by means of 2D superconducting fluctuations theory (Phys. Rev. B…
We first summarize our recent observations, through magnetization measurements in different low-Tc superconductors, of a rather sharp disappearance of the superconducting fluctuations in the normal state when the magnetic field approaches…
Non-Fermi liquid phenomena arise naturally near critical points of Landau ordering transitions in metallic systems, where strong fluctuations of a bosonic order parameter destroy coherent quasiparticles. Despite progress in developing…
We study the Kane-Mele-Hubbard model both at half-filling and away from half-filling using a slave-boson mean-field approach at zero temperature. We obtain a phase diagram at half-filling and discuss its connection to recent results from…
Motivated by the recent experimental realization of synthetic gauge fields in ultracold atoms, we investigate one-dimensional attractive Fermi gases with a time-dependent gauge flux on the spin sector. By combining the methods of the Bethe…
We consider the behavior of quasiparticles in the superconducting state of high-T_c metals within the framework of the theory of superconducting state based on the fermion condensation quantum phase transition. We show that the behavior…
Thermodynamic quantities are derived for superconducting and pseudogap regimes by taking into account both amplitude and phase fluctuations of the pairing field. In the normal (pseudogap) state of the underdoped cuprates, two domains have…
Implication of our recent proposal [J. Phys. Soc. Jpn. 65 (1996) 687] to treat large-amplitude gauge-field fluctuations around the slave-boson mean-field theory for the t-J model has been explored in detail. By attaching gauge flux to…
High-temperature superconductivity emerges in the CuO$_2$ plane upon doping a Mott insulator. To ascertain the influence of Mott physics plus short-range correlations, we solve a three-band copper-oxide model in the charge-transfer regime…
We study 1D fermions with photoassociation or with a narrow Fano-Feshbach resonance described by the Boson-Fermion resonance model. Using thebosonization technique, we derive a low-energy Hamiltonian of the system. We show that at low…