Energy Spectrum of Spin Fluctuations in Superconducting La_<2-x>Sr_xCuO_4(0.10≤x≤0.25) : Condensed Matter: Electronic Properties, etc.

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The energy spectrum of incommensurate spin fluctuations in superconducting Sr-doped La_2CuO_4 has been studied by inelastic neutron scattering experiments. An energy gap in the spin excitation spectrum is observed in the superconducting state of optimally doped (x = 0.15) and slightly overdoped (x = 0.18) samples. At temperatures well blow T_c, the incommensurate peaks diminish rapidly in intensity with decreasing energy below ~8meV and merge into the background below ~3.5meV for x = 0.15 and ~4.5meV for x = 0.18. For both samples, the energy spectrum of the q-integrated spin susceptibility, χ"(ω), exhibits an enhancement around 7meV, which is caused by a broadening in the momentum width of the incommensurate peaks. The gap-like structure in the energy spectrum and the enhancement of χ"(ω) survive at T_c. On the other hand, for both underdoped (x = 0.10) and heavily overdoped (x = 0.25) samples there is neither a clear energy gap nor an enhancement of χ"(ω) below T_c.
社団法人日本物理学会の論文
2000-04-15