1,647 research outputs found
Hysteretic current-voltage characteristics and resistance switching at an epitaxial oxide Schottky junction SrRuO/SrTiNbO
Transport properties have been studied for a perovskite heterojunction
consisting of SrRuO (SRO) film epitaxially grown on
SrTiNbO (Nb:STO) substrate. The SRO/Nb:STO interface
exhibits rectifying current-voltage (-) characteristics agreeing with
those of a Schottky junction composed of a deep work-function metal (SRO) and
an -type semiconductor (Nb:STO). A hysteresis appears in the -
characteristics, where high resistance and low resistance states are induced by
reverse and forward bias stresses, respectively. The resistance switching is
also triggered by applying short voltage pulses of 1 s - 10 ms duration.Comment: 3 pages, 3 figures, Appl. Phys. Lett., in pres
Theory of Josephson effect in chiral p-wave superconductor / diffusive normal metal / chiral p-wave superconductor junctions
We study the Josephson effect between chiral p-wave superconductor /
diffusive normal metal (DN) / chiral p-wave superconductor (CP/DN/CP) junctions
using quasiclassical Green's function formalism with proper boundary
conditions. The px+ipy-wave symmetry of superconducting order parameter is
chosen which is believed to be a pairing state in Sr2RuO4. It is shown that the
Cooper pairs induced in DN have an odd-frequency spin-triplet s-wave symmetry,
where pair amplitude is an odd function of Matsubara frequency. Despite the
peculiar symmetry properties of the Cooper pairs, the behavior of the Josephson
current is rather conventional. We have found that the current phase relation
is almost sinusoidal and the Josephson current is proportional to exp(-L/xi),
where xi is the coherence length of the Cooper pair in DN and L is the length
of DN. The Josephson current between CP / diffusive ferromagnet metal (DF) / CP
junctions is also calculated. It is shown that the 0-pi transition can be
realized by varying temperature or junction length L similar to the case of
conventional s-wave junctions. These results may serve as a guide to study
superconducting state of Sr2RuO4.Comment: 9 pages, 9 figure
Novel Orbital Ordering induced by Anisotropic Stress in a Manganite Thin Film
We performed resonant and nonresonant x-ray diffraction studies of a
Nd0.5Sr0.5MnO3 thin film that exhibits a clear first-order transition. Lattice
parameters vary drastically at the metal-insulator transition at 170K (=T_MI),
and superlattice reflections appear below 140K (=T_CO). The electronic
structure between T_MI and T_CO is identified as A-type antiferromagnetic with
the d_{x2-y2} ferroorbital ordering. Below T_CO, a new type of antiferroorbital
ordering emerges. The accommodation of the large lattice distortion at the
first-order phase transition and the appearance of the novel orbital ordering
are brought about by the anisotropy in the substrate, a new parameter for the
phase control.Comment: 4pages, 4figure
Multivalued memory effects in electronic phase-change manganites controlled by Joule heating
Non-volatile multivalued memory effects caused by magnetic fields, currents,
and voltage pulses are studied in Nd_{0.65}Ca_{0.35}MnO_3 and
(Nd_{1-y}Sm_{y})_{0.5}Sr_{0.5}MnO_3 (y=0.75) single crystals in the hysteretic
region between ferromagnetic metallic and charge-ordered insulating states. The
current/voltage effects observed in this study are explained by the
self-heating effect, which enable us to control the colossal electroresistance
effects. This thermal-cycle induced switching between electronic solid and
liquid states can be regarded as electronic version of atomic crystal/amorphous
transitions in phase-change chalcogenides.Comment: 5 pages, 4 figures. to appear in Phys. Rev.
Angular dependence of Josephson currents in unconventional superconducting junctions
Josephson effect in junctions between unconventional superconductors is
studied theoretically within the model describing the effects of interface
roughness. The particularly important issue of applicability of the frequently
used Sigrist-Rice formula for Josephson current in d-wave superconductor /
insulator / d-wave superconductor junctions is addressed. We show that although
the SR formula is not applicable in the ballistic case, it works well for rough
interfaces when the diffusive normal metal regions exist between the d-wave
superconductor and the insulator. It is shown that the SR approach only takes
into account the component of the d-wave pair potential symmetric with respect
to an inversion around the plane perpendicular to the interface. Similar
formula can be derived for general unconventional superconductors with
arbitrary angular momentum l.Comment: 4 pages, 4 figure
Theory of Josephson effect in Sr2RuO4/diffusive normal metal/Sr2RuO4 junctions
We derive a generalized Nazarov’s boundary condition for diffusive normal metal (DN)/chiral p-wave superconductor (CP) interface including the macroscopic phase of the superconductor. The Josephson effect is studied in CP/DN/CP junctions solving the Usadel equations under the above boundary condition. We find that, enhancement of a critical current at low temperature is small compared with that in px-wave /DN/px-wave junctions. As a result, temperature dependence of the critical current in these junctions is similar to that in conventional junctions. The result is consistent with the experiment in Sr2RuO4–Sr3RuO7 eutectic junctions. Similar feature is also found in current–phase relation
Crystallographic and superconducting properties of the fully-gapped noncentrosymmetric 5d-electron superconductors CaMSi3 (M=Ir, Pt)
We report crystallographic, specific heat, transport, and magnetic properties
of the recently discovered noncentrosymmetric 5d-electron superconductors
CaIrSi3 (Tc = 3.6 K) and CaPtSi3 (Tc = 2.3 K). The specific heat suggests that
these superconductors are fully gapped. The upper critical fields are less than
1 T, consistent with limitation by conventional orbital depairing. High,
non-Pauli-limited {\mu}0 Hc2 values, often taken as a key signature of novel
noncentrosymmetric physics, are not observed in these materials because the
high carrier masses required to suppress orbital depairing and reveal the
violated Pauli limit are not present.Comment: 8 pages, 8 figure
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