Intra-unit-cell magnetic correlations near optimal doping in YBa2Cu3O6.85

Area of Science:

• Condensed Matter Physics
• Materials Science
• Superconductivity

Background:

• The pseudo-gap phenomenon is a key characteristic of copper oxide superconductors, preceding the superconducting state.
• Magnetic intra-unit-cell order has been observed at the pseudo-gap temperature in several cuprate families.

Purpose of the Study:

• To investigate the nature of intra-unit-cell magnetic order in nearly optimally doped YBa2Cu3O6.85.
• To elucidate the relationship between this magnetic order and the pseudo-gap physics.

Main Methods:

• Polarized neutron-scattering measurements were performed on YBa2Cu3O6.85 using two different spectrometers.
• The study analyzed magnetic correlations and anisotropy at various temperatures.

Main Results:

• Intra-unit-cell order was found to comprise finite-sized planar domains weakly correlated along the c-axis.
• At high temperatures, only out-of-plane magnetic components correlated, indicating Ising anisotropy.
• An in-plane magnetic response emerged at low temperatures, causing an apparent tilt of the magnetic moment.

Conclusions:

• The observed magnetic order exhibits two distinct temperature regimes, strongly linked to pseudo-gap physics.
• These findings impose significant constraints on the intrinsic nature of intra-unit-cell order in cuprate superconductors.