title: Quantum Critical Origin of the Superconducting Dome in SrTiO_{3}.
abstract: We expand the well-known notion that quantum criticality can induce superconductivity by proposing a concrete mechanism for superconductivity due to quantum ferroelectric fluctuations. To this end, we investigate the origin of superconductivity in doped SrTiO_{3} using a combination of density functional and strong coupling theories within the framework of quantum criticality. Our density functional calculations of the ferroelectric soft mode frequency as a function of doping reveal a crossover related to quantum paraelectricity at a doping level coincident with the experimentally observed top of the superconducting dome. Thus, we suggest a model in which the soft mode fluctuations provide the pairing interaction for superconductivity carriers. Within our model, the low doping limit of the superconducting dome is explained by the emergence of the Fermi surface, and the high doping limit by departure from the quantum critical regime. We predict that the highest critical temperature will increase and shift to lower carrier doping with increasing ^{18}O isotope substitution, a scenario that is experimentally verifiable. Our model is applicable to other quantum paraelectrics, such as KTaO_{3}.
authors.affiliation: Nordita, Center for Quantum Materials, KTH Royal Institute of Technology and Stockholm University, Roslagstullsbacken 23, 10691 Stockholm, Sweden.
authors.forename: Jonathan M
authors.initials: JM
authors.lastname: Edge
authors.affiliation: Nordita, Center for Quantum Materials, KTH Royal Institute of Technology and Stockholm University, Roslagstullsbacken 23, 10691 Stockholm, Sweden.
authors.forename: Yaron
authors.initials: Y
authors.lastname: Kedem
authors.affiliation: Materials Theory, ETH Zurich, Wolfgang-Pauli-Strasse 27, CH-8093 Zürich, Switzerland.
authors.forename: Ulrich
authors.initials: U
authors.lastname: Aschauer
authors.affiliation: Materials Theory, ETH Zurich, Wolfgang-Pauli-Strasse 27, CH-8093 Zürich, Switzerland.
authors.forename: Nicola A
authors.initials: NA
authors.lastname: Spaldin
authors.affiliation: Nordita, Center for Quantum Materials, KTH Royal Institute of Technology and Stockholm University, Roslagstullsbacken 23, 10691 Stockholm, Sweden.|Institute for Materials Science, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA.
authors.forename: Alexander V
authors.initials: AV
authors.lastname: Balatsky