The interplay between superconductivity, magnetism and charge order have been extensively studied by using magnetic field or pressure as an external parameter to tune the systems to its critical regions. Here I will present a set of three works where extreme conditions have been used to study the stabilization domains of different superconducting phases.
The two first studies focus on the interplay between magnetism and unconventional superconductivity in the heavy-fermion compound UTe2. For this compound, multiple superconducting phases were found to be induced in the vicinity of a metamagnetic transition under magnetic field either at ambient pressure or combined with pressure. In the first study, electrical resistivity with a rotating magnetic field has been used in order to explore the enhancement of magnetic fluctuations in the vicinity of a field induced superconducting phase stabilized above 40 T. The second study focused on determining the magnetic structure under pressure using neutron diffraction.
For the last part, I will present a thermal expansion data set under pressure obtained on the kagome metal CsV3Sb5 which exhibits charge density wave phases (CDW) and superconductivity. Under pressure, two superconducting domes have been found to be stabilized at p ≈ 0.6 GPa and ≈ 2 GPa. Transitions found within the CDW phase suggest additional structure instabilities that may be related to the superconducting domes. In addition, sign changes of the Grüneisen parameter are observed in the vicinity of the two superconducting domes suggesting enhanced entropy that may be related to the superconducting pairing mechanism of these domes.
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