Isotope effect in superconducting n-doped SrTiO3

Stucky, A.; Scheerer, Gernot; Ren, Zhi; Jaccard, D.; Poumirol, Jean-Marie; Barreteau, Céline; Giannini, E.; Marel, D. van der

doi:10.1038/srep37582

Cited by 100 publications

(116 citation statements)

References 46 publications

(113 reference statements)

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“…Finally, the density of states ν in Eqs. (35) and (37) should be modified according to ν = ε F k F /2π 2 v 2 F . The decomposition of the Coulomb repulsion is more subtle.…”

Section: Possibility Of P-wave Pairingmentioning

confidence: 99%

Superconductivity near a Ferroelectric Quantum Critical Point in Ultralow-Density Dirac Materials

Kozii

Ruhman

2019

Phys. Rev. X

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The experimental observation of superconductivity in doped semimetals and semiconductors, where the Fermi energy is comparable to or smaller than the characteristic phonon frequencies, is not captured by the conventional theory. In this paper, we propose a mechanism for superconductivity in ultralow-density three-dimensional Dirac materials based on the proximity to a ferroelectric quantum critical point. We derive a low-energy theory that takes into account both the strong Coulomb interaction and the direct coupling between the electrons and the soft phonon modes. We show that the Coulomb repulsion is strongly screened by the lattice polarization near the critical point even in the case of vanishing carrier density. Using a renormalization group analysis, we demonstrate that the effective electron-electron interaction is dominantly mediated by the transverse phonon mode. We find that the system generically flows towards strong electron-phonon coupling. Hence, we propose a new mechanism to simultaneously produce an attractive interaction and suppress strong Coulomb repulsion, which does not require retardation. For comparison, we perform same analysis for covalent crystals, where lattice polarization is negligible. We obtain qualitatively similar results, though the screening of the Coulomb repulsion is much weaker. We then apply our results to study superconductivity in the low-density limit. We find strong enhancement of the transition temperature upon approaching the quantum critical point. Finally, we also discuss scenarios to realize a topological p-wave superconducting state in covalent crystals close to the critical point. :1901.11064v2 [cond-mat.supr-con] CONTENTS arXiv

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“…Finally, the density of states ν in Eqs. (35) and (37) should be modified according to ν = ε F k F /2π 2 v 2 F . The decomposition of the Coulomb repulsion is more subtle.…”

Section: Possibility Of P-wave Pairingmentioning

confidence: 99%

Superconductivity near a Ferroelectric Quantum Critical Point in Ultralow-Density Dirac Materials

Kozii

Ruhman

2019

Phys. Rev. X

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“…For example, Raman scattering found that the hardening of the FE soft mode in the dilute metal is indistinguishably similar to what is seen in the insulator [21]. The anomaly in resistivity was found to terminate at a threshold carrier density (n * ), near which the superconducting transition temperature was enhanced [21] providing evidence for a link between superconducting pairing and ferroelectricity, a subject of present attention [22][23][24][25][26][27][28][29][30][31][32].…”

Section: Introductionmentioning

confidence: 96%

Charge transport in a polar metal

et al. 2019

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The fate of electric dipoles inside a Fermi sea is an old issue, yet poorly-explored. Sr1−xCaxTiO3 hosts a robust but dilute ferroelectricity in a narrow (0.002 < x < 0.02) window of substitution. This insulator becomes metallic by removal of a tiny fraction of its oxygen atoms. Here, we present a detailed study of low-temperature charge transport in Sr1−xCaxTiO 3−δ , documenting the evolution of resistivity with increasing carrier concentration (n). Below a threshold carrier concentration, n * (x), the polar structural phase transition has a clear signature in resistivity and Ca substitution significantly reduces the 2 K mobility at a given carrier density. For three different Ca concentrations, we find that the phase transition fades away when one mobile electron is introduced for about 7.9±0.6 dipoles. This threshold corresponds to the expected peak in anti-ferroelectric coupling mediated by a diplolar counterpart of Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction. Our results imply that the transition is driven by dipole-dipole interaction, even in presence of a dilute Fermi sea. At higher carrier concentrations, our data resolves slight upturns in low-temperature resistivity in both Ca-free and Ca-substituted samples, reminiscent of Kondo effect and most probably due to oxygen vacancies.arXiv:1909.04278v1 [cond-mat.supr-con]

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“…If a ferroic phase transition can be suppressed to zerotemperature using a variable such as pressure or applied field, then the ordering is determined by quantum rather than thermal effects, resulting in exotic behavior even at finite temperatures. Such quantum criticality is well established for magnetic ordering, where it is believed to be responsible for example for heavy-fermion superconductivity, and has also recently been identified in ferroelectrics [90], where it is believed to be associated with the unconventional superconductivity in SrTiO 3 [91,92]. The concept of multiferroic quantum criticality ( Fig.…”

Section: Discussionmentioning

confidence: 97%

Multiferroics beyond electric-field control of magnetism

Spaldin

2020

Proc. R. Soc. A.

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Multiferroic materials, with their combined and coupled magnetism and ferroelectricity, provide a playground for studying new physics and chemistry as well as a platform for the development of novel devices and technologies. Based on my July 2017 Royal Society Inaugural Lecture, I review recent progress and propose future directions in the fundamentals and applications of multiferroics, with a focus on initially unanticipated developments outside of the core activity of electric-field control of magnetism.

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Isotope effect in superconducting n-doped SrTiO3

Cited by 100 publications

References 46 publications

Superconductivity near a Ferroelectric Quantum Critical Point in Ultralow-Density Dirac Materials

Superconductivity near a Ferroelectric Quantum Critical Point in Ultralow-Density Dirac Materials

Charge transport in a polar metal

Multiferroics beyond electric-field control of magnetism

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