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We performed inelastic neutron experiments on underdoped La_2-xSr_xCuO_4(x=0.10, T_c=28.6K) using a time-of-flight neutron scattering technique. Four incommensurate peaks on the two-dimensional reciprocal plane disperse inwards toward an antiferromagnetic zone center as the energy increases. These peaks merge into a single peak at an energy E_cross around w=40+-3meV. Beyond E_cross, the peak starts to broaden and ``hourglass-like excitations are observed. The E_cross in the underdoped sample is smaller than that reported for the optimally doped La_1.84Sr_0.16CuO_4. The reduction of the E_cross is explained by the doping-independent slope of the downward dispersion below the E_cross combined with the smaller incommensurability in the underdoped sample. In the energy spectrum of chi(w), we observed a similar peak-dip-hump structure in the energy region of 10~45meV to that reported for the optimally doped sample. We discuss the relation between the hourglass-shaped dispersion and the peak-dip-hump energy spectrum.
Inelastic neutron scattering measurements have been performed on underdoped Ba(Fe1-xCox)2As2 (x = 4.7%) where superconductivity and long-range antiferromagnetic (AFM) order coexist. The broad magnetic spectrum found in the normal state develops into
We report neutron scattering measurements of cooperative spin excitations in antiferromagnetically ordered BaFe2As2, the parent phase of an iron pnictide superconductor. The data extend up to ~100meV and show that the spin excitation spectrum is shar
We have determined the electron-coupling spectrum of superconducting Bi2Sr2CaCu2O8+d from high-resolution angle-resolved photoemission spectra by two deconvolution-free robust methods. As hole concentration decreases, the coupling spectral weight at
The evolution of electronic (spin and charge) excitations upon carrier doping is an extremely important issue in superconducting layered cuprates and the knowledge of its asymmetry between electron- and hole-dopings is still fragmentary. Here we comb
To explore the doping dependence of the recently discovered charge density wave (CDW) order in YBa2Cu3Oy, we present a bulk-sensitive high-energy x-ray study for several oxygen concentrations, including strongly underdoped YBa2Cu3O6.44. Combined with