# High-Tc superconductivity in strongly overdoped cuprates

Andrea Gauzzi, D. Hrabovsky, Hemmatzade Amirreza, Ludovic Delbes, Linda Sederholm, Maarit Karppinen, G. Allodi, Roberto de Renzi, Gianguido Baldinozzi, Edmondo Gilioli, et al.

► To cite this version:

Andrea Gauzzi, D. Hrabovsky, Hemmatzade Amirreza, Ludovic Delbes, Linda Sederholm, et al. High-Tc superconductivity in strongly overdoped cuprates. 8th international conference on superconductivity and magnetism, ICSM Conferences, May 2023, Fethiye, Turkey. hal-03946116

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https://cnrs.hal.science/hal-03946116

Submitted on 19 Jan 2023

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High-$T_c$ superconductivity in strongly overdoped cuprates

A. Gauzzi¹, Y. Klein¹, D. Hrabovsky², A. Hemmatzade¹, L. Delbes¹,
L. Sederholm³, M. Karppinen³, G. Allodi⁴, R. De Renzi⁴,
G. Baldinozzi⁵, E. Gilioli⁶ and S. D. Conradson⁷,⁸

¹IMPMC, Sorbonne Université, CNRS and MNHN, 4, Place Jussieu, Paris, France

²Department of Physics, Sorbonne Université, 4, Place Jussieu, Paris, France

³Department of Chemistry and Materials Science, Aalto University, 00076 Aalto, Finland

⁴Dpt of Mathematical, Physical and Computer Sciences, Univ. of Parma, 43124 Parma, Italy

⁵CNRS CentraleSupélec, Université Paris-Saclay, 91192 Gif-sur-Yvette, France

⁶CNR, Institute of Materials for Electronics and Magnetism, Parma, Italy

⁷Department of Complex Matter, Josef Stefan Institute, 1000 Ljubljana, Slovenia

⁸Department of Chemistry, Washington State University, Pullman, WA 90164, USA

It is widely accepted that, in the overdoped region, $p > 0.27$ hole/Cu, where superconductivity disappears, the properties of cuprates are conventional, i.e. Fermi-liquid like. In fact, until recently, such conventional scenario for overdoped cuprates has never been verified experimentally owing to the difficulty of overdoping the CuO₂ plane.

Here we report on the successful synthesis of high-purity polycrystalline samples of strongly overdoped YBa₂Cu₃O₇+х and Cu₀.75Mo₀.25Sr₂YCu₂O₇+х [1] with oxygen content, x, up to 0.4 (i.e. $p > 0.5$ hole/Cu, well beyond the superconducting dome) using a high-pressure oxygenation method at 4-6 GPa. Surprisingly, all samples exhibit bulk superconductivity in the 80-90 K range with little variations of $T_c$ as a function of x. This result is confirmed by the observation of a nearly x-independent superfluid density by muon-spin-relaxation spectroscopy. Remarkably, a common feature of both systems is a record short apical distance between the apical oxygen and the planar Cu atom, which points at a partial occupancy of both Cu $d_{x^2-y^2}$ and $d_z^2$ orbitals [2,3]. Low-temperature specific heat measurements suggest the existence of a significant fraction of unpaired electrons, consistent with a picture of electronic phase separation. Finally, a study of the local structure by means of Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy unveils huge (~1 Å) dynamical distortions of the lattice at $T_c$ that involve the apical oxygen [4,5], which reflects a lattice-driven change of the electronic structure in the superconducting state. The above unexpected results put into question the validity of the current phenomenological description of cuprates. Specifically, we discuss the possibility of multi-orbital superconductivity and the implications of the nonadiabatic scenario suggested by our experiments on the electron-lattice dynamics.

References

1. A. Gauzzi, Y. Klein, M. Nisula, M. Karppinen, P. K. Biswas, H. Saadaoui, E. Morenzoni, P. Manuel, D. Khalyavin, M. Marezio, and T. H. Geballe, Phys. Rev. B **94**, 180509(R) (2016).

2. D. J. Scalapino, Proc. Natl. Acad. Sci. USA **116**, 12129 (2019).

3. T. Maier, T. Berlijn, and D. J. Scalapino, Phys. Rev. B **99**, 224515 (2019).

4. S. D. Conradson, T. H. Geballe, A. Gauzzi, M. Karppinen, C.-Q. Jin, G. Baldinozzi, W. Li, L. Cao, E. Gilioli, J. M. Jiang, M. Latimer, O. Mueller, V. Nasretdinova, Proc. Natl. Acad. Sci. USA **117**, 4559 (2020).

5. S. D. Conradson, T. H. Geballe, C.-Q. Jin, L.-P. Cao, A. Gauzzi, M. Karppinen, G. Baldinozzi, W.-M. Li, E. Gilioli, J. M. Jiang, M. Latimer, O. Mueller, V. Nasretdinova, Proc. Natl. Acad. Sci. USA **117**, 33099 (2020).