166 research outputs found
Josephson junction arrays with d-wave-induced [phi]-phase-shifts
Using thin-¯lm ramp-type Josephson contacts between a high-Tc and a low-Tc super- conductor, experiments to study the dx2¡y2-wave-induced ¼-phase-shift e®ects in planar Josephson arrays have been enabled. The presented studies include the ¯rst experimental realization of various complex Josephson arrays with built-in ¼-phase shifts, investigations on the order parameter symmetry in various high-Tc cuprate superconductors, the ¯rst direct imaging of dx2¡y2-wave induced Josephson current counter\ud
°ow, and half-integer magnetic-°ux quantum e®ects in one- and two-dimensional array
Strong electronic correlation and strain effects at the interfaces between polar and nonpolar complex oxides
The interface between the polar LaAlO and nonpolar SrTiO layers has
been shown to exhibit various electronic and magnetic phases such as two
dimensional electron gas, superconductivity, magnetism and electronic phase
separation. These rich phases are expected due to the strong interplay between
charge, spin and orbital degree of freedom at the interface between these
complex oxides, leading to the electronic reconstruction in this system.
However, until now all of these new properties have been studied extensively
based on the interfaces which involve a polar LaAlO layer. To investigate
the role of the A and B cationic sites of the ABO polar layer, here we
study various combinations of polar/nonpolar oxide (NdAlO/SrTiO,
PrAlO/SrTiO and NdGaO/SrTiO) interfaces which are similar in
nature to LaAlO/SrTiO interface. Our results show that all of these new
interfaces can also produce 2DEG at their interfaces, supporting the idea that
the electronic reconstruction is the driving mechanism for the creation of the
2DEG at these oxide interfaces. Furthermore, the electrical properties of these
interfaces are shown to be strongly governed by the interface strain and strong
correlation effects provided by the polar layers. Our observations may provide
a novel approach to further tune the properties of the 2DEG at the selected
polar/nonpolar oxide interfaces.Comment: 5 pages, 4 figure
Macroscopic quantum tunneling and quasiparticle-tunneling blockade effect in s-wave/d-wave hybrid junctions
We have theoretically investigated macroscopic quantum tunneling (MQT) and
the influence of nodal quasiparticles and zero energy bound states (ZES) on MQT
in s-wave/ d-wave hybrid Josephson junctions. In contrast to d-wave/d-wave
junctions, the low-energy quasiparticle dissipation resulting from nodal
quasiparticles and ZES is suppressed due to a quasiparticle-tunneling blockade
effect in an isotropic s-wave superconductor. Therefore, the inherent
dissipation in these junctions is found to be very weak. We have also
investigated MQT in a realistic s-wave/d-wave (Nb/Au/YBCO) junction in which
Ohmic dissipation in a shunt resistance is stronger than the inherent
dissipation and find that MQT is observable within the current experimental
technology. This result suggests high potential of s-wave/d-wave hybrid
junctions for applications in quantum information devices.Comment: 4 pages, 3 figure
Atomically flat interface between a single-terminated LaAlO3 substrate and SrTiO3 thin film is insulating
The surface termination of (100)-oriented LaAlO3 (LAO) single crystals was
examined by atomic force microscopy and optimized to produce a
single-terminated atomically flat surface by annealing. Then the atomically
flat STO film was achieved on a single-terminated LAO substrate, which is
expected to be similar to the n-type interface of two-dimensional electron gas
(2DEG), i.e., (LaO)-(TiO2). Particularly, that can serve as a mirror structure
for the typical 2DEG heterostructure to further clarify the origin of 2DEG.
This newly developed interface was determined to be highly insulating.
Additionally, this study demonstrates an approach to achieve atomically flat
film growth based on LAO substrates.Comment: 4 pages, 3 figure
RSFQ Circuitry Using Intrinsic π-Phase Shifts
The latching of temporary data is essential in the rapid single flux quantum (RSFQ) electronics family. Its pulse-driven nature requires two or more stable states in almost all cells. Storage loops must be designed to have exactly two stable states for binary data representation. In conventional RSFQ such loops are constructed to have two stable states, e.g. by using asymmetric bias currents. This bistability naturally occurs when phase-shifting elements are included in the circuitry, such as pi-Josephson junctions or a pi-phase shift associated with an unconventional (d-wave) order parameter symmetry. Both approaches can be treated completely analogously, giving the same results. We have demonstrated for the first time the correct operation of a logic circuit, a toggle-flip-flop, using rings with an intrinsic pi-phase shift (pi-rings) based on hybrid high-Tc to low-Tc Josephson junctions. Because of their natural bistability these pi-rings improve the device symmetry, enhance operation margins and alleviate the need for bias current lines.\ud
\u
Admixtures to d-wave gap symmetry in untwinned YBa2Cu3O7 superconducting films measured by angle-resolved electron tunneling
We report on an \textit{ab}-anisotropy of and in
ramp-edge junctions between untwinned YBaCuO and % -wave
Nb. For these junctions, the angle with the YBaCuO
crystal b-axis is varied as a single parameter. The
A()-dependence presents 2-fold symmetry. The minima in
at suggest a real s-wave subdominant
component and negligible -wave or imaginary s-wave admixtures. The
()-dependence is well-fitted by 83% -, 15%
isotropic - and 2% anisotropic s-wave order parameter symmetry, consistent
with .Comment: 4 pages, 3 figures, to be published in Physical Review Letter
Magnetic-field induced resistivity minimum with in-plane linear magnetoresistance of the Fermi liquid in SrTiO3-x single crystals
We report novel magnetotransport properties of the low temperature Fermi
liquid in SrTiO3-x single crystals. The classical limit dominates the
magnetotransport properties for a magnetic field perpendicular to the sample
surface and consequently a magnetic-field induced resistivity minimum emerges.
While for the field applied in plane and normal to the current, the linear
magnetoresistance (MR) starting from small fields (< 0.5 T) appears. The large
anisotropy in the transverse MRs reveals the strong surface interlayer
scattering due to the large gradient of oxygen vacancy concentration from the
surface to the interior of SrTiO3-x single crystals. Moreover, the linear MR in
our case was likely due to the inhomogeneity of oxygen vacancies and oxygen
vacancy clusters, which could provide experimental evidences for the unusual
quantum linear MR proposed by Abrikosov [A. A. Abrikosov, Phys. Rev. B 58, 2788
(1998)].Comment: 5 pages, 4 figure
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