Two-gap s± -wave superconductivity at an oxide interface
After half a century of debate, superconductivity in doped SrTiO3 has come to the fore again with the discovery of interfacial superconductivity in the LaAlO3 /SrTiO3 heterostructures. While these interfaces share the interesting properties of bulk SrTiO3, quantum confinement generates a complex band structure involving bands with different orbital symmetries whose occupancy is tunable by electrostating doping. Multigap superconductivity has been predicted to emerge in LaAlO3 /SrTiO3 at large doping, with a Bose-Einstein condensation character at the Lifshtiz transition. In this article, we report on the measurement of the upper critical magnetic field Hc2 of superconducting (110)-oriented LaAlO3 /SrTiO3 heterostructures and evidence a two-gap superconducting regime at high doping. Our results are quantitatively explained by a theoretical model based on the formation of an unconventional s±-wave superconducting state with a repulsive coupling between the two condensates. ; This work was supported by the ANR PRC (QUANTOP), by the QuantERA ERA-NET Cofund in Quantum Technologies (Grant Agreement No. 731473) implemented within the European Union's Horizon 2020 Program (QUANTOX) and the Île de France SESAME program, by the PID2020-118479RB-I00, PID2020-112548RB-100 and Severo Ochoa FUNFUTURE (CEX2019-000917-S) projects of the Spanish Ministry of Science and Innovation (MCIN/AEI/10.13039/501100011033), by the Generalitat de Catalunya (2017 SGR 1377), by Sapienza Università di Roma, through the projects, Ateneo 2018 (Grant No. RM11816431DBA5AF), Ateneo 2019 (Grant No. RM11916B56802AFE), Ateneo 2020 (Grant No. RM120172A8CC7CC7), and by the Italian Ministero dell'Istruzione, dell'Università e della Ricerca, through the Project No. PRIN 2017Z8TS5B. G.S. acknowledges financial support from the Beatriu de Pinós Programme and the Ministry of Research and Universities of the Government of Catalonia, with research Grant No. 2019 BP 00207. ; With funding from the Spanish government through the 'Severo Ochoa Centre of ...