| dc.description |
Inelastic neutron scattering has been used to determine the dynamic spin fluctuations in an underdoped high-temperature superconductor YBCO<sub>6.8</sub> single crystal. The magnetic resonance, that occurs around 40 meV in overdoped samples, is shifted to a lower energy, E<sub>r</sub> = 34 meV. A constant ratio, E<sub>r</sub>/k<sub>B</sub>T<sub>C</sub> = 4.9 ± 0.2, almost independent of the doping level, is found. According to numerous theoretical approaches, this finding supports the idea that the resonance energy is proportional (approximately twice) to the superconducting gap. |
