D. Matthey

Field-effect experiments in NdBa2Cu3O7−δ ultrathin films using a SrTiO3 single-crystal gate insulator

We report on the electrostatic modulation of superconductivity in very thin films of cuprate superconductors using a field-effect device based on a SrTiO3 single-crystal gate insulator. A Tc modulation of 3.5 K and a 37% change of the normal state resistance have been observed in an epitaxial bilayer composed of an insulating PrBa2Cu3O7−δ layer deposited on top of a superconducting NdBa2Cu3O7−δ film, two unit cells thick. To achieve large electric fields, the thickness of the commercial dielectric single-crystal SrTiO3 substrate (also used as the gate insulator) was reduced to 110 μm. The dielectric properties of the gate insulator were characterized as a function of temperature and electric field and the magnitude of the field effect was quantified. A Tc enhancement of 2.8 K was obtained for an applied field of −1.8×106 V/m, corresponding to a polarization of −4 μC/cm2.

Electric-field-effect modulation of the transition temperature, mobile carrier density, and in-plane penetration depth of NdBa2Cu3O7-delta thin films.

We explore the relationship between the critical temperature T(c), the mobile areal carrier density n(2D), and the zero-temperature magnetic in-plane penetration depth lambda(ab)(0) in very thin underdoped NdBa(2)Cu(3)O(7-delta) films near the superconductor to insulator transition using the electric-field-effect technique. Having established consistency with a Kosterlitz-Thouless transition, we observe that T(KT) depends linearly on n(2D), the signature of a quantum superconductor to insulator transition in two dimensions with znu(over)=1, where z is the dynamic and nu is the critical exponent of the in-plane correlation length.

Electrostatic modulation of the electronic properties of Nb-doped SrTiO3 superconducting films

We have performed ferroelectric field effect experiments using an epitaxial heterostructure composed of ferroelectric Pb(Zr0.2Ti0.8)O3 and superconducting Nb-doped SrTiO3. The films were prepared on (001) SrTiO3 substrates by off-axis radio-frequency magnetron sputtering and pulsed-laser deposition. By switching the polarization field of the 500-A-thick Pb(Zr0.2Ti0.8)O3 layer, a large change of about 30% in resistivity and a 20% shift of Tc (ΔTc∼0.05 K) were induced in the 400-A-thick epitaxial Nb-doped SrTiO3 layer. The relationship between Tc and the electrostatically modulated average carrier concentration can be mapped onto the phase diagram of chemically doped SrTiO3.

Electrostatic modulation of the superconducting transition in thin NdBa2Cu3O7−δ films: the role of classical fluctuations

Abstract We have grown epitaxial Pb(Zr 0.2 Ti 0.8 )O 3 /NdBa 2 Cu 3 O 7− δ (PZT/NBCO) heterostructures and used the reversible ferroelectric polarization of Pb(Zr 0.2 Ti 0.8 )O 3 to electrostatically modulate the superconducting transition of thin NdBa 2 Cu 3 O 7− δ films. For ∼80 A thick NdBa 2 Cu 3 O 7− δ layers, reversing the ferroelectric polarization induces a 1 K change in the superconducting transition temperature. A Kosterlitz–Thouless (KT) analysis of the transitions has been used to extract the KT temperature T KT for the two polarization states. From the values obtained, one can extract the change in the zero temperature superfluid density ( n s (0)). We find that the data imply a 6% change in n s (0), a value consistent with the change in carrier density produced by the ferroelectric field effect.

Hall effect in underdoped GdBa 2 Cu 3 O 7 − δ thin films: Evidence for a crossover line in the pseudogap regime

We report on measurements of the resistivity and Hall coefficient in underdoped

Transport properties and fluctuations in underdoped GdBa{sub 2}Cu{sub 3}O{sub x} thin films

{\mathrm{GdBa}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{7\ensuremath{-}\ensuremath{\delta}}

Field effect and ferroelectric field effect in correlated oxide films

epitaxial thin films grown by off-axis magnetron sputtering. The films have been lithographically patterned allowing precise measurements of the temperature dependencies of the inverse Hall constant

Electrostatic tuning of the hole density in NdBa2Cu3O(7-delta) films and its effect on the Hall response.

{R}_{H}^{\ensuremath{-}1}

Transport properties of reduced SrTiO3 single crystal “thin films”

and of the Hall angle

Epitaxial ferroelectric oxide heterostructures

{\ensuremath{\theta}}_{H}.