293 research outputs found
Survival of the d-wave superconducting state near the edge of antiferromagnetism in the cuprate phase diagram
In the cuprate superconductor , hole doping in the
layers is controlled by both oxygen content and the degree of oxygen-ordering.
At the composition , the ordering can occur at room
temperature, thereby tuning the hole doping so that the superconducting
critical temperature gradually rises from zero to 20 K. Here we exploit this to
study the c-axis penetration depth as a function of temperature and doping. The
temperature dependence shows the d-wave superconductor surviving to very low
doping, with no sign of another ordered phase interfering with the nodal
quasiparticles. The only apparent doping dependence is a smooth decline of
superfluid density as Tc decreases.Comment: 4 pages, 3 figure
Bolometric technique for high-resolution broadband microwave spectroscopy of ultra-low-loss samples
A novel low temperature bolometric method has been devised and implemented
for high-precision measurements of the microwave surface resistance of small
single-crystal platelet samples having very low absorption, as a continuous
function of frequency. The key to the success of this non-resonant method is
the in-situ use of a normal metal reference sample that calibrates the absolute
rf field strength. The sample temperature can be controlled independently of
the 1.2 K liquid helium bath, allowing for measurements of the temperature
evolution of the absorption. However, the instrument's sensitivity decreases at
higher temperatures, placing a limit on the useful temperature range. Using
this method, the minimum detectable power at 1.3 K is 1.5 pW, corresponding to
a surface resistance sensitivity of 1 for a typical 1
mm1 mm platelet sample.Comment: 13 pages, 12 figures, submitted to Review of Scientific Instrument
Effective magnetic penetration depth in superconducting cylinders and spheres with highly anisotropic electrodynamics
Effective magnetic penetration depth and microwave surface impedance are
derived for anisotropic layered superconductors in the shape of spheres and
long cylinders, where the external magnetic field is applied in the plane of
the highly conducting layers to induce out-of-plane screening currents. The
results are extended by analytic continuation to highly anisotropic conductors
and to lossy superconductors at high frequency. The electrodynamics for the
general case of a superconductor or metal with arbitrary anisotropy are
presented. The treatment is then specialized to layered materials with
unixaxial anisotropy, in which the penetration depth for currents flowing
perpendicular to the layers, lambda_c, is much greater than that for in-plane
currents, lambda_a. Exact solutions are found in the limit lambda_a goes to
zero, and are expected to provide an accurate representation of many
experiments on cuprates and other layered superconductors, particularly on
grain-aligned powders.Comment: 9 pages, 4 figure
Observation of the Transverse Optical Plasmon in SmLa0.8Sr0.2CuO4-d
We present microwave and infrared measurements on SmLa0.8Sr0.2CuO4-d, which
are direct evidence for the existence of a transverse optical plasma mode,
observed as a peak in the c-axis optical conductivity. This mode appears as a
consequence of the existence of two different intrinsic Josephson couplings
between the CuO2 layers, one with a Sm2O2 block layer, and the other one with a
(La,Sr)O block layer. From the frequencies and the intensities of the
collective modes we determine the value of the compressibility of the two
dimensional electron fluid in the copper oxygen planes.Comment: REVTeX, 4 pages, 5 eps-figures, PRL, in pres
Superconducting Magnetization above the Irreversibility Line in Tl2Ba2CuO6
Piezolever torque magnetometry has been used to measure the magnetization of
superconducting Tl2Ba2CuO6. Three crystals with different levels of oxygen
overdoping were investigated in magnetic fields up to 10 Tesla. In all cases,
the magnetization above the irreversibility line was found to depart from the
behaviour M ~ ln(Hc2/H) of a simple London-like vortex liquid. In particular,
for a strongly overdoped (Tc = 15K) crystal, the remnant superconducting order
above the irreversibility line is characterized by a linear diamagnetic
response (M ~ H) that persists well above Tc and also up to the highest field
employed.Comment: RevTeX, 11 pages, 7 encapsulated PostScript figures, submitted to
Physical Review
Non-Locality and Strong Coupling in the Heavy Fermion Superconductor CeCoIn: A Penetration Depth Study
We report measurements of the magnetic penetration depth in single
crystals of CeCoIn down to 0.14 K using a tunnel-diode based,
self-inductive technique at 28 MHz. While the in-plane penetration depth tends
to follow a power law, , the data are better
described as a crossover between linear ({\it T} ) and
quadratic ({\it T} ) behavior, with the
crossover temperature in the strong-coupling limit. The {\it c}-axis
penetration depth is linear in {\it T}, providing evidence
that CeCoIn is a {\it d}-wave superconductor with line nodes along the
{\it c}-axis. The different temperature dependences of and
rule out impurity effects as the source of .Comment: 4 pages, 3 figure
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