Probing the nodal metal in LBCO with heat transport

The cuprate superconductor La$_x$Ba$_{2-x}$CuO$_4$ (LBCO) has a near-zero minimum in the superconducting transition temperature at $x=1/8$. This is accompanied by the emergence of static one-dimensional spin and charge ordering in ``stripes'' [1]. Spectroscopic measurements at the same doping in the normal state have shown that a gap with d-wave symmetry is present in the single particle spectrum [2]. One possible origin of this gap is the destruction of the coherence of the superconducting ground state by phase fluctuations, suppressing $T_c$ while leaving gapped but ``uncondensed'' Cooper pairs and nodal quasiparticles. We present measurements of the thermal conductivity of LBCO at very low temperature in both superconducting and field-induced nodal metal states. [1] P. Abbamonte et al., {\em Nature Physics} {\bf 1}, 155 (2005) [2] T. Valla et al., {\em Science.} 10.1126/1134742 (2006)