Transport in Ultraclean YBa$_2$Cu$_3$O$_7$: neither Unitary nor Born Impurity Scattering

TL;DR

This study measures thermal conductivity in ultraclean YBa₂Cu₃O₇ at low temperatures and high magnetic fields, revealing that impurity and vortex scattering behaviors differ from conventional assumptions in clean cuprate superconductors.

Contribution

It demonstrates that impurity scattering in ultraclean cuprates cannot be described by standard unitary or Born limits, and vortex scattering must be considered, challenging existing transport theories.

Findings

Impurity scattering in ultraclean YBa₂Cu₃O₇ deviates from traditional models.

Vortex scattering significantly affects quasiparticle transport.

Results explain the field-dependent thermal conductivity plateau in Bi-2212.

Abstract

The thermal conductivity of ultraclean YBa$_2$Cu$_3$O$_7$ was measured at very low temperature in magnetic fields up to 13 T. The temperature and field dependence of the electronic heat conductivity show that two widespread assumptions of transport theory applied to unconventional superconductors fail for clean cuprates: impurity scattering cannot be treated in the usual unitary limit (nor indeed in the Born limit), and scattering of quasiparticles off vortices cannot be neglected. Our study also sheds light on the long-standing puzzle of a sudden onset of a "plateau" in the thermal conductivity of Bi-2212 versus field.