DOE OSTI ยท 3021958
Upper critical magnetic field and multiband superconductivity in artificial high-๐ ๐ superlattices of nano quantum wells
Abstract
Artificial high-T c superlattices (AHTS) composed of quantum building blocks with tunable superconducting critical temperature have been synthesized by engineering their nanoscale geometry using the Bianconi-Perali Valletta (BPV) two-gap superconductivity theory. These quantum heterostructures consist of quantum wells made of superconducting, modulation-doped Mott insulators (S), confined by a metallic (N) potential barrier. The lattice geometry has been carefully engineered to induce the predicted Fano-Feshbach shape resonance between the gaps, near a topological Lifshitz transition. Here, we validate the BPV theory by providing compelling experimental evidence that AHTS samples, at the peak of the superconducting dome, exhibit resonant two-band, two-gap superconductivity. This is demonstrated by measuring the temperature dependence of the upper critical magnetic field, ฮผ 0 H c2 , in samples with superlattice periods 3.3 < d < 5.28 nm and L/d ratios close to the magic value 2/3 (where L is the thickness of the superconducting La 2 CuO 4 layer and d is the superlattice period). Here, the data reveal the predicted upward concavity in H c2 (T) and a characteristic kink in the coherence length as a function of temperature, confirming the predicted two-band superconductivity with Fermi velocity ratio โ 0.25 and significant pair-exchange term among the two condensates.
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Campi, Gaetano [Institute of Crystallography, Rome (Italy); Rome International Center for Materials Science Superstripes RICMASS (Italy)] (ORCID:0000000198459394), Alimenti, Andrea [Roma Tre University (Italy); Istituto Nazionale di Fisica Nucleare INFN, Sezione Roma Tre (Italy)] (ORCID:0000000244596147), Logvenov, Gennady [Max Planck Institute for Solid State Research, Stuttgart (Germany)] (ORCID:0000000319860249), Smith, G. Alexander [Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)], Balakirev, F. [Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)], Lee, Sang-Eon [Florida State University (FSU), Tallahassee, FL (United States)] (ORCID:0000000278276117), Balicas, Luis [Florida State University (FSU), Tallahassee, FL (United States)] (ORCID:0000000252090293), Silva, Enrico [Roma Tre University (Italy); Istituto Nazionale di Fisica Nucleare INFN, Sezione Roma Tre (Italy)] (ORCID:0000000186334295), Ummarino, Giovanni Alberto [Politecnico di Torino (Italy)] (ORCID:0000000262268518), Midei, Giovanni [University of Camerino (Italy); Istituto Nazionale di Fisica Nucleare, Sezione di Perugia (Italy)] (ORCID:000900088970291X), Perali, Andrea [University of Camerino (Italy); Rome International Center for Materials Science Superstripes RICMASS (Italy)] (ORCID:0000000249144975), Valletta, Antonio [Institute for Microelectronics and Microsystems, Rome (Italy)] (ORCID:0000000239019230), Bianconi, Antonio [Institute of Crystallography, Rome (Italy); Rome International Center for Materials Science Superstripes RICMASS (Italy)] (ORCID:0000000197953913). 2025-07-22. Upper critical magnetic field and multiband superconductivity in artificial high-๐ ๐ superlattices of nano quantum wells. https://doi.org/10.1103/k2yd-vpbn
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