397 research outputs found
Observation of two species of vortices in the anisotropic spin-triplet superconductor
Magnetic flux structures in single crystals of the layered spin triplet
superconductor SrRuO are studied by scanning micro SQUID Force
microscopy. Vortex chains appear as the applied field is tilted along the
in-plane direction of the superconductor. The vortex chains align along the
direction of the in-plane component of the applied magnetic field. The
decoration of in-plane vortices by crossing Abrikosov vortices is observed: two
vortex orientations are apparent simultaneously, one along the layers and the
other perpendicular to the layers. The crossing vortices appear preferentially
on the in-plane vortices
Magnetism of Superconducting UPt3
The phase diagram of superconducting in pressure-temperature
plane, together with the neutron scattering data is studied within a two
component superconducting order parameter scenario. In order to give a
qualitative explanation to the experimental data a set of two linearly
independent antiferromagnetic moments which emerge appropriately at the
temperature \mbox{} and \mbox{} and
couple to superconductivity is proposed. Several constraints on the fourth
order coefficients in the Ginzburg-Landau free energy are obtained.Comment: 17 pages, figures available on request to
[email protected]
Visualization by scanning SQUID microscopy of the intermediate state in the superconducting Dirac semimetal PdTe
The Dirac semimetal PdTe becomes superconducting at a temperature
~K. Thermodynamic and muon spin rotation experiments support type-I
superconductivity, which is unusual for a binary compound. A key property of a
type-I superconductor is the intermediate state which presents a coexistence of
superconducting and normal domains (flux structures) at magnetic fields lower
than the thermodynamic critical field . By means of scanning SQUID
microscopy (SSM) we observe flux structures in the superconducting state of
PdTe. The flux structures are strongly history dependent with a
transition from round shapes to laminar shapes as the magnetic field is more
and more increased. The field amplitudes measured at the surface are indicative
for the presence of Landau branching. The domain wall width in the intermediate
state has been determined.Comment: 8 pages 5 figure
Silicon Superconducting Quantum Interference Device
We have studied a Superconducting Quantum Interference SQUID device made from
a single layer thin film of superconducting silicon. The superconducting layer
is obtained by heavily doping a silicon wafer with boron atoms using the Gas
Immersion Laser Doping (GILD) technique. The SQUID device is composed of two
nano-bridges (Dayem bridges) in a loop and shows magnetic flux modulation at
low temperature and low magnetic field. The overall behavior shows very good
agreement with numerical simulations based on the Ginzburg-Landau equations.Comment: Published in Applied Physics Letters (August 2015
Observation of vortex coalescence in the anisotropic spin-triplet superconductor SrRuO
We present direct imaging of magnetic flux structures in the anisotropic,
spin-triplet superconductor SrRuO using a scanning SQUID
microscope. Individual quantized vortices were seen at low magnetic fields.
Coalescing vortices forming flux domains were revealed at intermediate fields.
Based on our observations we suggest that a mechanism intrinsic to the material
stabilizes the flux domains against the repulsive vortex-vortex interaction.
Topological defects like domain walls can provide this, implying proof for
unconventional chiral superconductivity.Comment: submitted to PR
Theory of Neutron Diffraction from the Vortex Lattice in UPt3
Neutron scattering experiments have recently been performed in the
superconducting state of UPt3 to determine the structure of the vortex lattice.
The data show anomalous field dependence of the aspect ratio of the unit cell
in the B phase. There is apparently also a change in the effective coherence
length on the transition from the B to the C phases. Such observations are not
consistent with conventional superconductvity. A theory of these results is
constructed based on a picture of two-component superconductivity for UPt3. In
this way, these unusual observations can be understood. There is a possible
discrepancy between theory and experiment in the detailed field dependence of
the aspect ratio.Comment: 11 pages; uses REVTEX, APS and PRABIB styles; 2 Postscript figure
files include
Nonlocality, Bell's Ansatz and Probability
Quantum Mechanics lacks an intuitive interpretation, which is the cause of a
generally formalistic approach to its use. This in turn has led to a certain
insensitivity to the actual meaning of many words used in its description and
interpretation. Herein, we analyze carefully the possible mathematical meanings
of those terms used in analysis of EPR's contention, that Quantum Mechanics is
incomplete, as well as Bell's work descendant therefrom. As a result, many
inconsistencies and errors in contemporary discussions of nonlocality, as well
as in Bell's Ansatz with respect to the laws of probability, are identified.
Evading these errors precludes serious conflicts between Quantum Mechanics and
both Special Relativity and Philosophy.Comment: 8&1/2 pages revtex; v2: many corrections, clairifications &
extentions, all small; v3: editorial scru
Channel Interference in a Quasi Ballistic Aharonov-Bohm Experiment
New experiments are presented on the transmission of electron waves through a
2DEG (2 dimensional electron gas) ring with a gate on top of one of the
branches. Magnetoconductance oscillations are observed, and the phase of the
Aharanov-Bohm signal alternates between 0 and pi as the gate voltage is
scanned. A Fourier transform of the data reveals a dominant period in the
voltage which corresponds to the energy spacing between successive transverse
modes.A theoretical model including random phase shifts between successive
modes reproduces the essential features of the experiment.Comment: 4 pages, 6 Postscript figures, TEX, submitted to Physical Review
Letter
Surface superconductivity and order parameter suppression in UPt
We show that a recent measurement of surface superconductivity in UPt
(Keller {\it et. al.}, Phys. Rev. Lett. {\bf 73}, 2364 (1994)) can be
understood if the superconducting pair wavefunction is suppressed
anisotropically at a vacuum to superconductor interface. Further measurements
of surface superconductivity can distinguish between the various
phenomenological models of superconducting UPt.Comment: 4 pages, latex, 2 Figures available upon request
([email protected]
Superconductivity in heavy-fermion U(Pt,Pd)3 and its interplay with magnetism
The effect of Pd doping on the superconducting phase diagram of the
unconventional superconductor UPt3 has been measured by (magneto)resistance,
specific heat, thermal expansion and magnetostriction. Experiments on single-
and polycrystalline U(Pt1-xPdx)3 for x<= 0.006 show that the superconducting
transition temperatures of the A phase, Tc+, and of the B phase, Tc-, both
decrease, while the splitting DTc increases at a rate of 0.30(2)K/at.%Pd. We
find that DTc(x) correlates with an increase of the weak magnetic moment m(x)
upon Pd doping. This provides further evidence for Ginzburg-Landau scenarios
with magnetism as the symmetry breaking field, i.e. the 2D E representation and
the 1D odd parity model. Only for small splittings DTc is proportional to
m^2(Tc+) (DTc<= 0.05 K) as predicted. The results at larger splittings call for
Ginzburg-Landau expansions beyond 4th order. The tetracritical point in the B-T
plane persists till at least x= 0.002 for B perpendicular to c, while it is
rapidly suppressed for B||c. Upon alloying the A and B phases gain stability at
the expense of the C phase.Comment: 25 pages text (PS), 8 pages with 14 figures (PS), submitted to
Phys.Rev.
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