We experimentally investigated optical, electrical, and microstructural properties of heterointerfaces between two thin-film perovskite insulating materials, ${\mathrm{SrTiO}}_{3}$ (STO) ${\mathrm{LaAlO}}_{3}$ (LAO), deposited at different oxygen pressure conditions. Cathode photoluminescence experiments show that vacancies are formed in the bulk STO substrate during growth LAO films, resulting high electrical conductivity mobility values. In both low interfaces, Hall mobilities follow a...

We present intrinsic tunneling spectroscopy measurements on small Bi2Sr2CaCu2O8+x mesas. The tunnel conductance curves show both sharp peaks at the superconducting gap voltage and broad humps representing c-axis pseudogap. vanishes Tc, while pseudogap exists above below Tc. Our observation implies that pseudogaps represent different coexisting phenomena.

We have studied weak links and dc–SQUIDs made from pulsed laser deposited YBa2Cu3O7−δ thin films on Y–ZrO2 bicrystal substrates. The transport properties of the were as a function misorientation angle (θ) between two halves an exponential dependence link critical current density was observed for angles up to 40° at 77 K. Josephson effects with clear microwave magnetic field responses observed. An optimum dc–SQUID performance K obtained θ=32°. At this temperature, we achieved periodic...

We have obtained convincing experimental evidence of the time correlation single-electron tunneling (SET) events, i.e., SET oscillations with average frequency ${f}_{s}$ fundamentally related as ${f}_{s}$=I/e to dc current I. The experiments been carried out one-dimensional N-junction arrays Al/oxide/Al tunnel junctions area S\ensuremath{\approxeq}0.006 \ensuremath{\mu}${\mathrm{m}}^{2}$ at T\ensuremath{\approxeq}60 mK. showed up resonance peaks dynamic resistance dV/dI a function I, arising...

The conductance of a normal $\left(N\right)$ mesoscopic silver or antimony conductor, to which superconducting $\left(S\right)$ aluminum wire is attached at two points, oscillates when control current in the superconductor varied. amplitude oscillations ranges from $2\ifmmode\times\else\texttimes\fi{}{10}^{2}({e}^{2}/h)$ for Ag/Al $5.3\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}2}({e}^{2}/h)$ Sb/Al structures...

The escape rate from the zero voltage state in a superconducting Josephson junction (JJ) is determined by temperature, but it saturates at low temperature due to macroscopic quantum tunneling (MQT). Complications d-wave symmetry high superconductor, like energy quasiparticles and an unconventional current-phase relation, may influence rate. We report, for first time our knowledge, observation of MQT YBa(2)Cu(3)O(7-delta) grain boundary biepitaxial JJ. This proves that dissipation can be...

Single-electron tunneling in Al/${\mathrm{AlO}}_{\mathrm{x}}$/Al junctions with areas below 0.01 \ensuremath{\mu}${\mathrm{m}}^{2}$ was studied at temperatures close to 1 K. The junctions, placed different high-frequency environments but similar all other aspects, exhibited dc I-V curves, accordance the theory of correlated single-electron tunneling. Our results imply that a electron can effectively probe its electrodynamic environment distances much larger than...

Stacked series arrays of intrinsic Josephson tunnel junctions have been fabricated on the surfaces ${\mathrm{Bi}}_{2}{\mathrm{Sr}}_{2}\mathrm{Ca}{\mathrm{Cu}}_{2}{\mathrm{O}}_{8+\ensuremath{\delta}}$ single crystals using photolithography and Ar-ion milling together with in situ monitoring resulting current-voltage ($I\ensuremath{-}V$) characteristics. The number stack (along $c$ axis) is varied from 1-5 to \ensuremath{\sim}200 a controlled way. Both coupling multiple branches well developed...

We present x-ray-absorption fine-structure (XAFS) measurements for a series of Co- and Fe-substituted samples $\mathrm{Y}{\mathrm{Ba}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{7\ensuremath{-}\ensuremath{\delta}}$ (Y-Ba-Cu-O). Our analysis the first- second-neighbor environments indicates that Co atoms primarily replace Cu in chain sites, Cu(1) atoms, Y-Ba-Cu-O, but many these Co(1) sites their neighboring oxygen are highly distorted. The first-neighbor Co-O peak consists \ensuremath{\sim}3.5 at 1.8...

Medium-energy ion spectroscopy (MEIS) has been used to study the depth profile and deduce distribution of possible cationic substitutions in LaAlO3/SrTiO3 (LAO/STO) heterointerfaces. Analysis La Sr peaks aligned random MEIS spectra indicates that surface layers LAO on an STO substrate are not homogeneous stoichiometric if film thickness is less than 4 unit cell layers. This possibly caused by a redistribution at interface. Kelvin probe force microscopy reveals inhomogeneous potential film,...

Coulomb blockade of single-electron tunneling and high sensitivity to an external electric field has been observed for 1D series arrays ultra-small-area (<0.1\ifmmode\times\else\texttimes\fi{}0.1 \ensuremath{\mu}${\mathrm{m}}^{2}$) tunnel junctions, made Al/${\mathrm{Al}}_{\mathrm{x}}$${\mathrm{O}}_{\mathrm{y}}$/Al, at helium temperatures. In particular, the dc voltage V across array responds strongly a ${U}_{g}$ applied control electrode. For thirteen gain...

Here we present the direct observation of macroscopic quantum properties in an all high-critical-temperature superconductor d-wave Josephson junction. Although dissipation caused by low-energy excitations is expected to strongly suppress effects, demonstrate energy level quantization our The result indicates that role mechanisms high-temperature superconductors has be revised, and it may also have consequences for class solid-state "quiet" bits with superior coherence time.

The interface between two wide band-gap insulators, LaAlO3 and SrTiO3 (LAO/STO), hosts a quasi-two-dimensional electron gas (q2DEG), two-dimensional superconductivity, ferromagnetism, giant Rashba spin-orbit coupling. co-existence of superconductivity with gate-tunable coupling multiband occupation is particular interest for the realization unconventional superconducting pairing. To investigate symmetry order parameter, phase sensitive measurements Josephson effect are required. We describe...

Electromagnetic resonances along a ${\mathrm{YBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7\mathrm{\ensuremath{-}}\mathrm{\ensuremath{\delta}}}$ bicrystal grain boundary junction made it possible to determine the ratio between barrier/boundary thickness and relative dielectric constant ${\mathit{t}}_{\mathit{d}}$/${\mathrm{\ensuremath{\varepsilon}}}_{\mathit{r}}$, London penetration depth ${\ensuremath{\lambda}}_{\mathit{L}}$, estimate surface resistance ${\mathit{R}}_{\mathit{s}}$ at...

An integrated receiver consisting of two Josephson flux-flow oscillators and a superconductor-insulator-superconductor (SIS) mixer has been used to measure the linewidth oscillators. The are coupled SIS using centerfed interdigital capacitors, one which with fairly weak (−20 dB) coupling. By biasing (a few microvolt apart) on their velocity matching steps, resulting oscillations (280–330 GHz) were mixed in mixer. difference frequency was amplified detected spectrum analyzer. combined 2.1 MHz...

We have fabricated and investigated submicron-size (0.01 0.04 \ensuremath{\mu}${\mathrm{m}}^{2}$) Pb-alloy single Josephson junctions attached to high-resistance thin-film NiCr or Cr leads which provide the necessary conditions for a strong charging effect. When coupling energy is less than energy, we find novel shape of current-voltage curves, with Coulomb gap at small voltages, current peak larger voltages. A theory based on concept incoherent Cooper-pair tunneling has explained data well.

We have measured the current-voltage (IV) characteristics of several two-dimensional arrays small Josephson junctions as a function temperature, T and magnetic field B. The relatively large charging energies ${\mathit{E}}_{\mathit{C}}$\ensuremath{\approxeq}1 K, normal-state resistances ${\mathit{R}}_{\mathit{N}}$ in range 4--150 k\ensuremath{\Omega}. From IV we can deduce zero-bias resistance ${\mathit{R}}_{0}$ threshold voltage ${\mathit{V}}_{\mathit{t}}$ which reveal important information...

X-ray-absorption fine-structure (XAFS) spectroscopy was employed to study the near-neighbor environments of Bi and Pb atoms in perovskite-structured material ${\mathrm{BaBi}}_{\mathit{x}}$${\mathrm{Pb}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{O}}_{3}$, for x=1, 0.75, 0.5, 0.25. For semiconducting end member, ${\mathrm{BaBiO}}_{3}$, two Bi-O distances, separated by 0.18 \AA{}, could be distinguished, consistent with diffraction results. After alloying Pb, distances are still observed...

The time correlation of tunneling events has been predicted to occur in ultrasmall tunnel junctions: a periodic with frequency determined by the current f=I/e. To test predictions, we have fabricated one-dimensional arrays Al/${\mathrm{Al}}_{\mathit{x}}$${\mathrm{O}}_{\mathit{y}}$/Al junctions areas down 0.006 \ensuremath{\mu}${\mathrm{m}}^{2}$ corresponding capacitances \ensuremath{\sim}0.2 fF. Each array contained between 15 and 53 junctions. Current-voltage characteristics were measured...

X-ray absorption studies of ${\mathrm{La}}_{1.8}$${\mathrm{Sr}}_{0.2}$${\mathrm{CuO}}_{4}$ and ${\mathrm{La}}_{1.8}$${\mathrm{Ba}}_{0.2}$${\mathrm{CuO}}_{4}$ indicate that no structural transition alters the valence or near-neighbor environment by >0.01 A\r{} occurs between 4 300 K. The doping with Sr Ba primarily changes Cu-O distance width along c axis. larger superconducting region observed in Ba-doped material may result from its static disorder. Estimates vibrational frequencies...

X-ray-absorption measurements of the high-${T}_{c}$ superconductors $\mathrm{Y}{\mathrm{Ba}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{7\ensuremath{-}\ensuremath{\delta}}$ and $\mathrm{Gd}{\mathrm{Ba}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{7\ensuremath{-}\ensuremath{\delta}}$ show that their near-edge extended fine structures (EXAFS) are essentially identical over temperature range 4.2 to 688 K. The results indicate not only very similar each other in local bonding electronic structure, but also remain...

Arrays of 10 or 40 series-connected small densely packed Josephson tunnel junctions were successfully operated as parametric amplifiers at GHz. Between 50 and 90% the in an array observed to work coherently amplification process. Signal gain exceeding 24 dB was achieved with a pump power low −50 −70 dBm. A width (i.e., range for within 3 peak gain) 0.25 bandwidth 15 MHz measured 20-dB gain. The accordance theory but reduced, probably due noise saturation effects. latter effects can be...

The quasi-two dimensional electron gas formed at the interface between LaAlO3 (LAO) and SrTiO3 (STO) shows fascinating properties, such as two-dimensional superconductivity, giant electric field effect, possible co-existence of ferromagnetic superconducting phases. In this work, we demonstrate that conducting LAO/STO can be made insulating after short irradiation by a beam low energy Ar+ ions. process does neither result in physical removal LAO film nor produces oxygen vacancies STO layer....

${\mathrm{PrBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7}$ (PBCO) is unique in the R${\mathrm{Ba}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7}$ (R=rare earth) series because it not superconducting. In fact, for ${\mathrm{Y}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{Pr}}_{\mathit{x}}$${\mathrm{Ba}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7}$, ${\mathit{T}}_{\mathit{c}}$ drops monotonically with Pr concentration, going to zero at \ensuremath{\sim}55% Pr. There have been many studies of this...