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arXiv · 2508.05196

Electronic mean free path of the cuprate superconductor Bi$_2$Sr$_2$CaCu$_2$O$_{8+δ}$ from thermal Hall conductivity

Emma Campillo·Manel Mezidi·Lu Chen·Ashvini Vallipuram·Jordan Baglo·Munkhtuguldur Altangerel·Gaël Grissonnanche·Genda Gu·Louis Taillefer
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Abstract

We use thermal transport to access the electronic mean free path of $d$-wave quasiparticles in one of the most widely studied cuprate superconductors, Bi$_2$Sr$_2$CaCu$_2$O$_{8+δ}$ (Bi2212). We have measured the thermal conductivity $κ_{\rm xx}$ and the thermal Hall conductivity $κ_{\rm xy}$ of three single crystals across a range of dopings. In the overdoped and optimally-doped samples, a clear enhancement is observed in both $κ_{\rm xx}$ and $κ_{\rm xy}$ upon cooling below the critical temperature $T_{\rm c}$, due to a suppression of the inelastic electron-electron scattering as electrons condense into pairs. The underdoped sample shows no enhancement in either, pointing to a high degree of disorder in that sample. For the two highest dopings, the magnitude of the enhancement in $κ_{\rm xy}$ is controlled by the strength of the elastic impurity scattering. Using a prior model to estimate the mean free path from $κ_{\rm xy}$ data, we find that the mean free path in Bi2212 is approximately 7 times shorter than in YBa$_2$Cu$_3$O$_7$, considered to be one of the least disordered cuprates. We conclude that the thermal Hall technique is a good way to compare the mean free path of $d$-wave quasiparticles in various cuprate materials.

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Emma Campillo, Manel Mezidi, Lu Chen, Ashvini Vallipuram, Jordan Baglo, Munkhtuguldur Altangerel, Gaël Grissonnanche, Genda Gu, Louis Taillefer. 2025-08-07. Electronic mean free path of the cuprate superconductor Bi$_2$Sr$_2$CaCu$_2$O$_{8+δ}$ from thermal Hall conductivity. https://arxiv.org/abs/2508.05196

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