4 research outputs found
Local Measurement of Microwave Response with Local Tunneling Spectra Using Near Field Microwave Microscopy
We have designed and built a near-field scanning microwave microscope, which
has been used to measure the local microwave response and the local
density-of-states (LDOS) in the area including the boundary between the gold
deposited and the non-deposited region on highly-orientated pyrolytic graphite
at a frequency of about 7.3 GHz. We have succeeded in measuring the spatial
variation of both the LDOS and the surface resistance. It can be observed that
the surface resistance in gold deposited region with the metallic tunneling
spectra is smaller than that in the non-deposited region with the U-shaped
tunneling spectra.Comment: 3 pages, 3 figures
Vortex fluctuations in underdoped Bi2Sr2CaCu2O8+d crystals
Vortex thermal fluctuations in heavily underdoped Bi2Sr2CaCu2O8+d (Tc=69.4 K)
are studied using Josephson plasma resonance (JPR). From the data in zero
magnetic field, we obtain the penetration depth along the c-axis,
lambda_{L,c}(0) = 229 micrometers and the anisotropy ratio gamma(0) = 600. The
low plasma frequency allows us to study phase correlations over the whole
vortex solid (Bragg-glass) state. The JPR results yield a wandering length
r_{w} of vortex pancakes. The temperature dependence of r_{w} as well as its
increase with applied dc magnetic field can only be explained by the
renormalization of the tilt modulus by thermal fluctuations, and suggest the
latter is responsible for the dissociation of the vortices at the first order
transition.Comment: 4 pages, 5 figures. Submitted to Phys. Rev. Let