Related papers: Distinct charge and spin gaps in underdoped YBa2Cu…
We show that there are strong similarities in the spin lattice relaxation of non-magnetic organic charge transfer salts, and that these similarities can be understood in terms of spin fluctuations. Further, we show that, in all of the…
The electronic Raman scattering in overdoped (Y,Ca)Ba2Cu3Oy was investigated with changing hole concentration in the superconducting state. It was found that the superconducting responses such as the pair-breaking peaks in the A1g and B1g…
We determine the magnetic phase diagram for the YBa$_2$Cu$_3$O$_{6+x}$ and La$_{2-x}$Sr$_x$CuO$_4$ systems from various NMR experiments. We discuss the possible interpretation of NMR and neutron scattering experiments in these systems in…
Recent excperiments (ARPES, Raman) suggest the presence of two distinct energy gaps in high-Tc superconductors (HTSC), exhibiting different doping dependences. Results of a variational cluster approach to the superconducting state of the…
The properties of the pseudogap phase above Tc of the high-Tc cuprate superconductors are described by showing that the Anderson-Nambu SU(2) spinors of an RVB spin gap 'lock' to those of the electron charge system because of the resulting…
The temperature dependences of g factors of underdoped YBa2Cu3O7-x (Tc approximates 86.5K) indicate that the pseudogap onset temperature T*( approximates 190 K) coincides with the phase boundary established by resistivity, Nernst effect,…
$^{63}$Cu and $^{199}$Hg NMR shifts for an optimally and underdoped HgBa$_{2}$CuO$_{4+\delta}$ single crystal are reported, and the temperature dependence dictates a two-component description of the uniform spin susceptibility. The first…
The spin and charge excitations of the t--J ladder are studied by exact diagonalization techniques for several electron densities. The various modes are classified according to their spin (singlet or triplet excitations) and their parity…
We describe results of electronic Raman-scattering experiments in differently doped single crystals of Y-123 and Bi-2212. The comparison of AF insulating and metallic samples suggests that at least the low-energy part of the spectra…
When pairing correlations in a quasi two dimensional electron system induce a pseudogap in the single particle density of states, the specific heat must also contain a sizeable pair contribution. The theoretically calculated specific heat…
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 for the pseudogap. The pseudogap arises…
We have studied magnetic excitations in the dimerized spin-Peierls phase of CuGeO3, by high resolution inelastic neutron scattering. We measured the well-defined spin triplet dispersive mode which is gapped throughout the whole Brillouin…
A central issue in the quest to understand the superconductivity in cuprates is the nature and origin of the pseudogap state, which harbours anomalous electronic states such as Fermi arc, charge density wave (CDW), and $d$-wave…
Cluster perturbation theory is applied to the two-dimensional Hubbard $t-t'-t''-U$ model to obtain doping and temperature dependent electronic spectral function with $4 \times 4$ and 12-site clusters. It is shown that evolution of the…
We propose an explanation of several experimental features of transport phenomena in the normal state of high Tc cuprates in terms of a spin-charge gauge theory of the 2D t-J model. The calculated doping-temperature dependence for a number…
High resolution neutron scattering measurements on a single crystal of SrCu(2-x)Mgx(BO3)2 with x=0.05 reveal the presence of new spin excitations within the gap of this quasi-two dimensional, singlet ground state system. Application of a…
Using neutron scattering we have determined the magnetic structure and fluctuations in the YBa2Cu3O6.35 superconductor (Tc=18 K). The long-range ordered collinear spins of the insulating antiferromagnet are replaced by a commensurate…
We present electron-tunneling spectroscopy of oxygen over- and under-doped Bi-2212 single crystals in a temperature range between 14 K and 290 K using a break-junction technique. In over- and under-doped samples we observe a pseudogap with…
The comprehensive study of the temperature dependent x-ray absorption spectroscopy (XAS) reveals a dynamical spectral weight $\alpha$ in YBa$_2$Cu$_3$O$_y$ (YBCO). Large spectral weight changes for both the Upper Hubbard band and the…
Key properties of the cuprates, such as the pseudogap observed above the critical temperature $T_c$, remain highly debated. Given their importance, we recently proposed a novel mechanism based on the Bose-like condensation of mutually…