CDT-CMP Cohort 2 Student Jake Ayres, co-authors paper ‘Charge Order and Superconductivity in Underdoped YBa2Cu3O7−δ under Pressure’, in collaboration with Carsten Putzke, Jonathan Buhot, Salvatore Licciardello, Nigel E. Hussey, Sven Friedemann, and Antony Carrington. This paper can be read here.

Superconducting materials transmit electricity with zero loss and have already found their way into modern technologies from MRI scanners and high-performance generators to particle accelerators. Future candidate technologies are numerous but the extremely low temperatures are which they operate are holding back their adoption into more mainstream technologies. Despite decades of research, fully understanding the superconducting state in high temperature superconductors like the cuprate family of materials has proved to be difficult.

The cuprate family of materials are famed for their high superconducting transition temperatures which can be tuned by doping and enhanced to above 150K with the application of pressure. Understanding the origin of superconductivity in these materials is complicated by the presence of multiple other exotic electronic phases which may interact with superconductivity in complex ways. For example, it has been shown that there is a marked suppression of superconductivity in samples doped such that they have feature a charge density wave.

In this work, we studied the electronic properties of YBa2Cu3O7−δ (a member of the cuprate family of superconductors) under both pressure and in high-magnetic fields in order to shed light on the interplay between superconductivity and the charge density wave state. By measuring the temperature dependence of the change of sign of the Hall coefficient, an indicator of the onset of charge order, and the superconducting transition we were able to track the strengths of these phases as we increased hydrostatic pressure up to 2.6GPa. We discovered that despite substantially enhancing superconductivity, very little effect was felt by the charge density wave. The implication is that these two phases are not in mutually exclusive competition as previous studies have suggested.