Journal
ADVANCED MATERIALS INTERFACES
Volume 9, Issue 29, Pages -Publisher
WILEY
DOI: 10.1002/admi.202201392
Keywords
field-effect device; multiband; oxide interfaces; superconductivity
Funding
- French CNRS
- ANR PRC (QUANTOP)
- French RENATECH network (French national nanofabrication platform)
- DGA
- project Quantox of QuantERA ERA-NET Cofund in Quantum Technologies [731473]
- COST project Nanocohybri-Action [CA16218]
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This study elaborates on a generic scenario for the superconducting phase diagram of SrTiO3-based interfaces. The optimal doping point of maximum critical temperature (Tc) is attributed to the transition between different superconducting states. The dependence of Tc on carrier density exhibits a bifurcation phenomenon, which can be controlled by the details of the doping execution. Different doping methods result in different filling behaviors and superconducting states, providing a generic explanation for the dome-shaped superconducting phase diagram.
A dome-shaped phase diagram of superconducting critical temperature upon doping is often considered as a hallmark of unconventional superconductors. This behavior, observed in SrTiO3-based interfaces, whose electronic density is controlled by field-effect, has not been explained unambiguously yet. Here, a generic scenario for the superconducting phase diagram of these oxide interfaces is elaborated based on transport experiments on a double-gate LaAlO3/SrTiO3 field-effect device and Schrodinger-Poisson numerical simulations of the quantum well. The optimal doping point of maximum T-c is ascribed to the transition between a single-gap and a fragile two-gap s(+/-)-wave superconducting state involving bands of different orbital character. Close to this point, a bifurcation in the dependence of T-c on the carrier density, which can be controlled by the details of the doping execution, is observed experimentally and reproduced by numerical simulations. Where doping with a back-gate triggers the filling of a new dxy${d_{{\rm{xy}}}}$ subband and initiates the overdoped regime, doping with a top-gate delays the filling of the subband and maintains the 2D electron gaz in the single-gap state of higher T-c. Such a bifurcation, whose branches can be followed reversibly, provides a generic explanation for the dome-shaped superconducting phase diagram that could be extended to other multiband superconducting materials.
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