Related papers: Fermi liquid behavior and spin-charge separation i…
A series of LiFe$_{1-x}$Co$_{x}$As compounds with different Co concentrations have been studied by transport, optical spectroscopy, angle-resolved photoemission spectroscopy and nuclear magnetic resonance. We observed a Fermi liquid to…
We study the spin fluctuations of pure and Zn-substituted high temperature superconductors (HTS) using the muon spin relaxation (muSR) technique. Superconductivity is found to coexist with low frequency spin fluctuations over a large region…
The pseudogap effect of underdoped high-$T_c$ superconductors is studied in the U(1) gauge theory of the t-J model including the spinon pairing fluctuation. The gauge fluctuation breaks the long range correlation between the spinon pairs.…
A unified theory is outlined for the cuprates, Fe-based, and related superconductors. Their low-energy excitations are approached in terms of auxiliary particles representing combinations of atomic-like electron configurations, and the…
Based on the t-J model and the self-consistent Born approximation, the damping of quasiparticle hole states near the Fermi surface is calculated in a low doping regime. Renormalization of spin-wave excitations due to hole doping is taken…
We investigated the temperature- and frequency-dependent optical scattering rates in the pseudogap phase of cuprates using model pseudogap and electron-boson spectral density (EBSD) functions. We obtained the scattering rates at various…
Based on an unconventional Fermi liquid model, we present several results on the optimally doped and overdoped cuprate superconductors. For the normal state, we provide an analytic demonstration, backed by self-consistent Baym-Kadanoff (BK)…
The change-over from phase- to amplitude-fluctuation driven superconductivity is examined for a composite system of free electrons (Fermions with concentration n_F) and localized electron-pairs (hard-core Bosons with concentration n_B) as a…
Spin fluctuation-induced superconductivity in quasi-two dimensional organic compounds, \kappa-BEDT-TTF salts, is investigated within a fluctuation exchange (FLEX) approximation using a half-filled Hubbard model with a right-angled isosceles…
We investigate the superfluid phase transition and effects of mass imbalance in the BCS (Bardeen-Cooper-Schrieffer)-BEC (Bose-Einstein condensation) crossover regime of an cold Fermi gas. We point out that the Gaussian fluctuation theory…
A comprehensive study of doped RVB states is performed. It reveals a fundamental connection between superconductivity and quantum spin fluctuations in underdoped cuprates : {\em Cooper pair hopping} strongly reduces the local magnetization…
A characteristic feature of the Gaussian approximation in the functional-integral approach to the spin-fluctuation theory is the jump phase transition to the paramagnetic state. We eliminate the jump and obtain a continuous second-order…
We consider a magnetic impurity coupled to both fermionic quasiparticles with a pseudogap density of states and bosonic spin fluctuations. Using renormalization group and large-N calculations we investigate the phase diagram of the…
The normal-state charge transport is studied systematically in high-quality single crystals of BaFe$_2$(As$_{1-x}$P$_x$)$_2$ ($0 \leq x \leq 0.71$). By substituting isovalent P for As, the spin-density-wave (SDW) state is suppressed and the…
We use an SU(2) mean-field theory approach with input from variational wavefunctions of the t-J model to study the electronic spectra in the pseudogap phase of cuprates. In our model, the high-temperature state of underdoped cuprates is…
Inspired by the recent discovery of superconductivity in the nickelate Nd$_{1-x}$Sr$_x$NiO$_2$, we study a generalized $t-J$ model to investigate the correlated phases induced by doping spin-one Ni$^{2+}$ into a spin $1/2$ Mott insulator…
High-Tc superconducting materials (HTSC) have anomalous properties such as the pseudo-gap or spin-gap etc., in Hall coefficient, 1/T1T and the density of states etc. First including effects of strong on-site repulsion between d-electrons at…
Whether the doped t-J model on the Kagome lattice supports exotic superconductivity has not been decisively answered. In this paper, we propose a new class of variational states for this model and perform large-scale variational Monte Carlo…
We propose a microscopic model Hamiltonian to account for impurity doping induced insulator-superconductor transition and the coexistence of antiferromagnetism and superconductivity in the high-Tc cuprates. The crossover from non Fermi…
Qualitative changes in thermodynamic and single-particle properties characterize the transition between the pseudogapped electronic liquid and the Fermi liquid. Recent cold-atom experiments on a simulator of the Hubbard model with…