High pressure

High pressures at very low temperatures

Recently, the interplay of magnetism and superconductivity has attracted great interest with the discovery of several compounds in which a superconducting phase appears at the border of a magnetic order. These materials provide an important route to the understanding of superconductivity mediated by spin fluctuations associated with a magnetic quantum critical point (QCP). In most cases, these novel superconductors are based on either cerium or uranium. Of particular relevance is the influence of antiferromagnetism and superconductivity on each other in the cerium compounds that under pressure lose their antiferromagnetic ordering at a critical pressure around which emerges the superconducting state.

By implementing magnetic penetration depth measurements at pressures as high as 3 GPa in the low-temperature region down to 30 mK we will be able to study the order parameter symmetry near the QCP of the noncentrosymmetric Ce-compounds like CeIrSi3, CeRhSi3, and CeCoGe3. Apart from these compounds, we will pay special attention to CePtSi3, a noncentrosymmetric superconductor that has no QCP but which antiferromagnetic phase fades away under pressure.