Join the Quantum Matter group in a seminar titled "High-Tc superconductivity in strongly overdoped cuprates" with Prof. Andrea Gauzzi (IMPMC, Sorbonne University).

Date: 25 November 2022, 2:00PM - 3:00PM

Zoom Link: https://bristol-ac-uk.zoom.us/j/98775390060?pwd=MFNQQTFlc3ZHalZiWEthcGxoSXNLZz09

Meeting ID: 987 7539 0060 

Passcode: 329952

Abstract:

For over three decades, research on superconducting cuprates has been focused on the underdoped and optimally doped regions of the electronic phase diagram, where these materials display an unconventional normal state – or “strange metal” – properties. It is widely accepted that, in the overdoped region at p > 0.27 hole/Cu, where superconductivity disappears, the properties are conventional, i.e. Fermi-liquid like. In fact, until recently, this region has been little studied owing to the difficulty of overdoping the CuO₂ plane, so such conventional scenario for overdoped cuprates has never been verified experimentally in a systematic manner.

Here we present recent results that give evidence of high-T_c superconductivity in a number of cuprates, such as Cu_0.75Mo_0.25Sr₂YCu₂O_7.54 [1], Ba₂CuO_4-y [2] and La_2-xCa_xCuO₄ [3], where strong overdoping, p > 0.4 hole/Cu, is achieved using high-pressure oxygenation during synthesis. In order to investigate the superconducting properties in this unusual region of the phase diagram, we studied the local structure of the above compounds by means of Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy. To our surprise, we found huge (~1 Å) dynamical distortions of the lattice at T_c that involve the apical oxygen [4,5], which suggests the existence of 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 [6,7]. Specifically, we shall discuss the possibility of multi-orbital superconductivity [8] and the consequences of the nonadiabatic scenario suggested by our experiments on the description of the electron-lattice dynamics [5].