Breakdown of universal transport in correlated d-wave superconductors.

The prediction and observation of low-temperature universal thermal conductivity in cuprates has served as a keystone of theoretical approaches to the superconducting state, but recent measurements on underdoped samples show strong violations of this apparently fundamental property of d-wave nodal quasiparticles. Here, we show that the breakdown of universality may be understood as the consequence of disorder-induced magnetic droplets arising from enhanced antiferromagnetic correlations in the underdoped state, even as these same correlations protect the nodal density of states.