The quantum critical point of cuprate superconductors

I will present recent experimental studies performed using high magnetic fields to suppress superconductivity and access the non-superconducting ground state of cuprates in the T = 0 limit. These reveal the presence of a quantum critical point in the phase diagram of cuprates [1,2,3], where the enigmatic pseudogap phase ends, around which the superconducting phase forms a dome, and at which the resistivity exhibits an anomalous linear dependence on temperature [4,5].

In particular, our recent measurements of the normal-state specific heat C(T) down to very low temperature (0.5 K) reveal clear thermodynamic signatures of a quantum critical point, with C/T showing a sharp peak at the pseudogap critical doping p*, and C/T ~ log(1/T) at p = p*.

Strong similarities with the quantum critical point at which antiferromagnetic order ends in organic [6], iron-based [7], heavy-fermion [8] and electron-doped cuprate [9] superconductors suggest that antiferromagnetic spin correlations also play a fundamental role in hole-doped cuprates. The outstanding questions are : Does antiferromagnetic order extend up to the critical point in hole-doped cuprates ? Is long-range order necessary to open a (pseudo)gap and generate anomalous, non-Fermi-liquid, scattering and mass renormalization down to T ~ 0 ?

[1] S. Badoux et al., Nature 531, 210 (2016).
[2] C. Collignon et al., Phys. Rev. B 95, 224517 (2017).
[3] B. Michon et al., to be published.
[4] R. Daou et al., Nat. Phys. 5, 31 (2009).
[5] L. Taillefer, Annu. Rev. Condens. Matter Phys. 1, 51 (2010); arXiv:1003.2972.
[6] N. Doiron-Leyraud et al., Phys. Rev. B 80, 214531 (2009).
[7] T. Shibauchi, A. Carrington, Y. Matsuda, Annu. Rev. Condens. Matter Phys. 5, 113 (2014).
[8] P. Monthoux, D. Pines, G. G. Lonzarich, Nature 450, 1177 (2007).
[9] N. P. Armitage, P. Fournier, R. L. Greene, Rev. Mod. Phys. 82, 2421 (2010).