We report an unprecedented observation of a transition between single-condensate to two-condensate superconductivity. The experiments were done using resonant microwave transport carried out in the Laboratoire de Physique et d'Etude des Matériaux, ESPCI Paris, enabling continuous and reversible transitions between the two condensate regimes via electrostatic gating of LaAlO3/SrTiO3 quantum wells.
Gap suppression at a Lifshitz transition in a multi-condensate superconductor
Gyanendra Singh, Alexis Jouan, Gervasi Herranz, Mateusz Scigaj, Florencio Sánchez, Lara Benfatto, Sergio Caprara, Marco Grilli, Guilhem Saiz, François Couëdo, Cheryl Feuillet-Palma, Jérôme Lesueur, Nicolas Bergeal
Nature Materials 18, 948–954, 2019
Figure: Superconducting phase diagram. We plot the gap energies of the two condensates Δ1(0) and Δ2(0) (left axis) and γ coefficient (right axis), which accounts for the weight of each condensate in the LaAlO3/SrTiO3 quantum well. These magnitudes are plotted as a function of the voltage gate (VG) and are superimposed on the sheet resistance color map.