CUPRES

This project aims to advance our understanding of the electronic structure of high Tc cuprate superconductors. In particular, we will use the unique combination of high pressure and high magnetic fields to study the evolution of two phases which exist alongside the superconducting state, namely the so-called pseudogap state and a charge ordered state. Both of these states have end points which approximately coincide with the point on the doping-temperature phase diagram where the superconducting transition temperature is maximal and it has been suggested that fluctuations in the order parameter of one or both of these phases could be responsible for the electron pairing that leads to high temperature superconductivity. Most studies to date of these phase, and indeed the cuprates in general, have used chemical doping to tune the materials across their phase diagram. Instead we plan to use pressure, which is a complementary tuning parameter which we expect to split the accidental phase degeneracies which complicate the interpretation of the doping dependent studies. Our experimental programme includes studies of Hall co-efficient, quantum oscillations and magnetic penetration depth to elucidate the changes in electronic structure. We will also perform x-ray studies under uniaxial stress to correlate changes in electronic structure to structural changes caused by the charge order.