Thermal Hall conductivity of mercury-based cuprate superconductors

Measurements of the thermal Hall conductivity κ_xy in d-wave superconductors can be used to extract the mean free path of d-wave quasiparticles inside the superconducting state [1]. Here we report measurements of two mercury-based cuprates: single-layer Hg1201 (underdoped with T_c = 72 K) and triple-layer Hg1223 (underdoped with T_c = 78 K and 112 K). The latter holds the record for the highest critical temperature of all known superconductors (at ambient pressure), namely T_c = 133 K at optimal doping.

We compare our data with corresponding data on high-quality samples of YBCO, known to have some of the longest electronic mean free paths [2].

We find that κ_xy increases significantly upon cooling below T_c, reflecting the reduction in electron-electron scattering as charge carriers pair in the superconducting state.

We discuss the possible role of antiferromagnetic and charge orders [3] in affecting the electronic mean free path.

[1] Krishana et al., Phys. Rev. Lett. 82, 5108 (1999).

[2] Zhang et al., Phys. Rev. Lett. 86, 890 (2001).

[3] Oliviero et al., Nat. Commun. 13, 1568 (2022).