Shifting of the magnetic resonance peak to lower energy in the superconducting state of underdoped YBa_2Cu_3O_{6.8}

TL;DR

This study uses inelastic neutron scattering to observe a shift in the magnetic resonance peak to lower energy in underdoped YBCO_{6.8}, revealing a nearly doping-independent ratio to T_C, supporting theories linking resonance energy to the superconducting gap.

Contribution

It provides experimental evidence of the resonance energy shift in underdoped YBCO and confirms its proportionality to the superconducting gap across doping levels.

Findings

Resonance peak shifts from 40 meV to 34 meV in underdoped samples.

The ratio E_r / (k_B T_C) remains nearly constant at 4.9 ± 0.2.

Supports the idea that resonance energy is proportional to the superconducting gap.

Abstract

Inelastic neutron scattering has been used to determine the dynamic spin fluctuations in an underdoped high temperature superconductor YBCO_{6.8} single crystal. The magnetic resonance, that occurs around 40 meV in overdoped samples, is shifted to a lower energy, E_r= 34 meV. A constant ratio, $E_r/ k_B T_C= 4.9 \pm 0.2$, 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.