Polar Nanodomains in a Ferroelectric Superconductor

Salmani-Rezaie, Salva; Ahadi, Kaveh; Stemmer, Susanne

doi:10.1021/acs.nanolett.0c02285

Cited by 43 publications

(30 citation statements)

References 46 publications

(84 reference statements)

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“…For example, it has been reported that in-plane compressive strain can enhance the T C of SrTiO 3 by up to a factor of two, resulting from the strain-induced modification of phonon modes [39]. More study further revealed that both strain and disorder could control T C [40,41]. A systematic increase of T C with epitaxial tensile strain in MgB 2 films has also been reported, resulted from the softening of the bondstretching phonon mode [42].…”

Section: Resultsmentioning

confidence: 96%

Ultrathin epitaxial NbN superconducting films with high upper critical field grown at low temperature

Wei

Roy

Yang

et al. 2021

Materials Research Letters

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Ultrathin (5-50 nm) epitaxial superconducting niobium nitride (NbN) films were grown on AlNbuffered c-plane Al 2 O 3 by an industrial scale physical vapor deposition technique at 400°C. Both X-ray diffraction and scanning electron microscopy analysis show high crystallinity of the ( 111)oriented NbN films, with a narrow full-width-at-half-maximum of the rocking curve down to 0.030°. The lattice constant decreases with decreasing NbN layer thickness, suggesting lattice strain for films with thicknesses below 20 nm. The superconducting transition temperature, the transition width, the upper critical field, the irreversibility line, and the coherence length are closely correlated to the film thickness. IMPACT STATEMENTThis work realized high quality ultrathin epitaxial NbN films by an industry-scale PVD technology at low substrate temperature, which opens up new opportunities for quantum devices.

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Section: Resultsmentioning

confidence: 96%

Ultrathin epitaxial NbN superconducting films with high upper critical field grown at low temperature

Wei

Roy

Yang

et al. 2021

Materials Research Letters

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“…This sensitivity, combined with the low temperatures, makes detailed characterization of the structure of the quantum paraelectric state challenging: Neutron and x-ray Rietveld analysis of STO, for example, indicate a centrosymmetric structure down to 1.5 K [15]. In contrast, nuclear magnetic resonance (NMR) shows local dynamic polar off-centering of the Ti ions [16], consistent with the anomalous vibrational amplitudes seen in γ-ray Bragg scattering [17], and scanning transmission electron microscopy reveals local polar nanoregions [18].…”

Section: Introductionmentioning

confidence: 92%

Ferroelectric, quantum paraelectric or paraelectric? Calculating the evolution from BaTiO$_3$ to SrTiO$_3$ to KTaO$_3$ using a single-particle quantum-mechanical description of the ions

Esswein,

Spaldin

2021

Preprint

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We present an inexpensive first-principles approach for describing quantum paraelectricity that combines density functional theory (DFT) treatment of the electronic subsystem with quantum mechanical treatment of the ions through solution of the single-particle Schrödinger equation with the DFT-calculated potential. Using BaTiO3, SrTiO3 and KTaO3 as model systems, we show that the approach can straightforwardly distinguish between ferroelectric, paraelectric and quantum paraelectric materials, based on simple quantities extracted from standard density functional and density functional perturbation theories. We calculate the influence of isotope substitution and strain on the quantum paraelectric behavior, and find that, while complete replacement of oxygen-16 by oxygen-18 has a surprisingly small effect, experimentally accessible strains can induce large changes. Finally, we collect the various choices for the phonon mass that have been introduced in the literature. We identify those that are most physically meaningful by comparing with our results that avoid such a choice through the use of mass-weighted coordinates.

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“…Moreover, SrTiO 3 can also be a polar superconductor that undergoes a ferroelectric transition prior to becoming superconducting. [3][4][5] In superconductors with broken inversion symmetry spin-orbit coupling becomes important, which can lead to unconventional superconductivity. [6][7][8][9] A test of the nature of a superconductor is its response to disorder.…”

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confidence: 99%

“…Surprisingly, however, the superconducting transition temperatures (T c ) and the superconducting dome are identical for magnetic and non-magnetic dopants. 3,23,24 While there are indications that disorder from the dopant atoms is detrimental to superconductivity in SrTiO 3 , 5 the insensitivity to their magnetic moment does not easily fit within a conventional picture of isolated magnetic impurities that would strongly suppress the transition temperature of the superconductor.…”

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confidence: 99%

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Superconductivity in magnetically doped SrTiO3

Salmani-Rezaie

Galletti

Schumann

et al. 2021

Applied Physics Letters

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Doped SrTiO 3 is a superconductor whose pairing mechanism is still not fully understood. The response of a superconductor to impurities has long been used to obtain insights into the nature of the superconducting state. Here, the superconductivity of SrTiO 3 films that are doped or alloyed with different rare earth ions, which carry a magnetic moment, is investigated. It is shown that large concentrations (up to a few percent) of rare earth ions with unpaired f-electrons, such as Sm and Eu, do not reduce the superconducting critical temperature and critical fields. The finding is independent of whether the rare earth ion acts as a dopant or is an isovalent impurity. The interactions between the superconducting condensate and the magnetic dopants that could result in the observed insensitivity to magnetic impurities are discussed.

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Polar Nanodomains in a Ferroelectric Superconductor

Cited by 43 publications

References 46 publications

Ultrathin epitaxial NbN superconducting films with high upper critical field grown at low temperature

Ultrathin epitaxial NbN superconducting films with high upper critical field grown at low temperature

Ferroelectric, quantum paraelectric or paraelectric? Calculating the evolution from BaTiO$_3$ to SrTiO$_3$ to KTaO$_3$ using a single-particle quantum-mechanical description of the ions

Superconductivity in magnetically doped SrTiO3

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