[en] Highlights: • High-T_C cuprates. • (π,π) magnetic resonance. • Fauque et al.’s zero-momentum antiferromagnetism. • Pseudogap. • Theory of the magnetic resonance. - Abstract: The magnetic response expected from a state characterized by rotating antiferromagnetism in a neutron-scattering experiment is calculated. We predict the occurrence of a peak at the frequency of the rotation of the rotating antiferromagnetic order parameter. The doping dependence trends of this frequency are very similar to those of the frequency of the magnetic resonance observed in neutron-scattering experiments for the hole-doped high-T_C cuprates. This leads us to propose the rotating antiferromagnetism as a possible mechanism for this magnetic resonance. Also, the interpretation of the rotating order parameter as a probability for a spin flip process to occur allows us to argue that the unusual zero momentum antiferromagnetic order observed by Fauqué et al. is equivalent to the rotating antiferromagnetism phenomenon. We conclude that while the magnitude of the rotating antiferromagnetic order parameter was previously proposed to be responsible for the pseudogap and the unusual thermodynamic and transport properties, the phase of the rotating order parameter is proposed here to be responsible for the unusual magnetic properties of the high-T_C cuprate superconductors

[en] This paper is about the frustration-induced criticality in the antiferromagnetic Heisenberg model on the two-leg ladder with exchange interactions along the chains, rungs, and diagonals, and also about the effect of thermal fluctuations on this criticality. The method used is the bond-mean-field theory, which is based on the Jordan-Wigner transformation in dimensions higher than one. In this paper, we will summarize the main results presented in a talk, and report on new results about the couplings and temperature dependences of the spin susceptibility. (author)

[en] The phase of the rotating order parameter in rotating antiferromagnetism is calculated using a combination of mean-field theory and Heisenberg equation. This phase shows a linear time dependence, which allows us to interpret rotating antiferromagnetism as a synchronized Larmor-like precession of all the spins in the system or as an unusual q = (π,π) spin-wave around a zero local magnetization. We discuss implications for the pseudogap state of high-T_C superconducting materials. Rotating antiferromagnetism has been proposed to model the pseudogap state in these materials.

[en] Highlights: • In the underdoped to optimally doped regime, the pseudogap is observed in the optical conductivity spectra. • In the overdoped regime the pseudogap disappears and the optical conductivity behaves almost like the Drude conductivity. • In the overdoped regime, the trends like the cross-over region and the pseudogap signature in the optical conductivity were recover by this model. • The optical conductivity in the normal state is dominated by pseudogap and in the superconducting state it is dominated by unusual excitation. - Abstract: We studied the optical conductivity of Bi₂Sr₂CaCu₂O${}_{8+\delta }$ material as a function of temperature and doping within the Rotating Antiferromagnetism Theory (RAFT). The optical conductivity of the material is studied from underdoped to overdoped regime for a wide range of temperatures. We mainly focused on the pseudogap state and unusual excitations in the optical conductivity. The former is realized in the underdoped to optimally doped regimes below a characteristic temperature T*, a temperature that can appreciably exceed the superconducting transition temperature T_C. The latter is appeared in the optical conductivity spectra below the T_C and we studied it by varying temperature. The pseudogap response is explored by changing the doping level and by varying the temperature from above to below T*. The results obtained from theories are compared with available experimental data and found a good agreement with those experimental results.

[en] Concentrations of Hg, Pb, Cd, Cu and Zn have been measured in clam samples collected in eastern Algerian coast (El-Kala). Total of 280 samples have been collected between March 1993 and March 1994 at two stations

[en] The doping dependence of the Fermi surface and energy distribution curves of the high-T_C cuprate materials La_2-xSr_xCuO₄ and Bi₂Sr₂CaCu₂O_8+δ are analyzed within the rotating antiferromagnetism theory. Using three different quantities; the k-dependent occupation probability, the spectral function, and the chemical potential (energy spectra), the Fermi surface is calculated and compared to experimental data for La_2-xSr_xCuO₄. The Fermi surface we calculate evolves from hole-like pockets in the underdoped regime to large electron-like contours in the overdoped regime. This is in agreement with recent findings by Sebastian et al for the α-pocket of Y Ba₂Cu₃O_6+x (2010 Phys. Rev. B 81 214524). In addition, the full width at half maximum of the energy distribution curves is found to behave linearly with their peak position in agreement with experiment for Bi₂Sr₂CaCu₂O_8+δ. The effect of scattering on both the Fermi surface and energy distribution curves is examined.

[en] The ⁷Be + p elastic cross section has been measured at the Centre de Recherches du Cyclotron RIB facility at Louvain-la-Neuve in the c.m. energy region from 0.3 to 0.75 MeV by bombarding a proton-rich target with a radioactive ⁷Be beam. The recoil protons have been detected in the angular range θ_c.m. = 120.2 deg. - 131.1 deg. and θ_c.m. = 156.6 deg. - 170.2 deg. using the LEDA system. From a R-matrix analysis of the cross section data, we extract the energy and the width of the 1⁺ resonance. The scattering lengths α₀₁ = 25 ± 9 fm (channel spin I = 1) and α₀₂ = -7 ± 3 fm (channel spin I = 2) are deduced. Implications on the low energy S-factor of the ⁷Be(p, γ)⁸B reaction are discussed

[en] The motion of holes on the triangular lattice is studied using the t-J model. Within the Born self-consistent approximation and the exact Lanczos diagonalization, the single-hole physics is first analyzed. Then the spiral phase theory of Shraiman and Siggia is used to investigate the case of a finite density of holes. copyright 1996 The American Physical Society

[en] The ⁷Be+p elastic cross section has been measured at the Centre de Recherches du Cyclotron RIB facility at Louvain-la-Neuve in the c.m. energy region from 0.3 to 0.75 MeV by bombarding a proton-rich target with a radioactive ⁷Be beam. The recoil protons have been detected in the angular range θ_c.m.=120.2 deg. -131.1 deg. and θ_c.m.=156.6 deg. -170.2 deg. using the LEDA system. From a R-matrix analysis of the cross section data, we obtain the energy and the width of the 1⁺ resonance (E_x=0.77 MeV). The l=0 scattering lengths a₀₁=25±9 fm (channel spin I=1) and a₀₂=-7±3 fm (channel spin I=2) have been deduced. They are compared to values expected from charge-symmetry properties. Implications on the low energy S-factor of the ⁷Be(p, γ)⁸B reaction are discussed

[en] We studied the optical conductivity of the Bi₂Sr₂CaCu₂O_8+δ materials in the normal state as well as in the superconducting state as a function of temperature and doping within the rotating antiferromagnetism theory (RAFT) using the Marginal Fermi Liquid (MFL) ansatz for self-energy. The optical conductivity is calculated using Nambu formalism and Kubo’s formula. Experimental data for Bi₂Sr₂CaCu₂O_8+δ are discussed.