1,721,017 research outputs found
In-plane and out of plane resistivities in BiSrCaCuO(2212) single crystals at different doping level.
No full textUsing an eight terminal geometry in standard current/voltage contact configurations we have determined both the out-of-plane and the in-plane d.c. resistivity in BSCCO(2212) samples at different doping level. Comparison of the temperature behaviors for these transport quantities highlights that use of these configurations results in incorrect determinations for the in-plane components. Exploiting the possibility of crossed comparisons when using a multi-terminal technique we are able to ascribe this effect at presence on the sample of surface layer with oxygen contents different from the bulk
Resistivity tensor in the normal state of BSCCO single crystals as a function of doping
No full textWe present measurements of the resistivity tensor of Bi2Sr2CaCu2O8+δ single crystals with different oxygen concentrations. Sample doping varies from underdoped to slightly overdoped. Measurements are performed through multiterminal technique, which allows for a simultaneous determination of both in-plane and out-of-plane components of the resistivity tensor. Data are analyzed in terms of a model that assumes two different mechanisms for the out-of-plane conduction, markedly thermal activation and incoherent tunneling. Within this model we are able to describe data of normal state resistivity for all samples with different doping levels. We also analyze data from the literature. In all cases, the proposed model describes very well the data in the normal state
Fluctuation-induced resistivity in YBCO across Tc from angular measurements in magnetic field
No full textExcess conductivity of overdoped Bi2Sr2CaCu2O8+x crystals well above Tc.
No full textWe have used a multiterminal technique in order to measure the (a,b) plane excess conductivity Δσ in several Bi2Sr2CaCu2O8+x single crystals. We find that the experimental Δσ does not follow a simple power law Δσ∼ε-α, with ε=ln(T/Tc), and that it drops faster than the two-dimensional Aslamazov-Larkin law, α=1, with increasing temperature. In addition, data for samples with different doping do not scale on a universal curve. We discuss our data in terms of microscopic and Ginzburg-Landau theories, where high-momentum fluctuations are either not excited, or phenomenologically cut off. The experimental Δσ drops even faster than the prediction of the extended microscopic theory. However, we can accurately describe all our data up to T≈1.3 Tc with the GL theory, assuming a sample-dependent cutoff value. We relate the cutoff parameter to the doping level of our samples
Experimental determination of the fluctuational dissipation in YBCO up to high magnetic fields
No full textDetermination of the resistivity components rhoab and rho c from multi-terminal measurements in BiSrCaCuO crystals
No full text
Magnetic field orientation dependence of the microwave response in YBa2Cu3O7-d.
No full textWe present microwave resistivity measurements at 21 GHz in YBa2Cu3O7-δ thin film as a function of the temperature and the magnetic field. Measurements are taken in various relative orientations of the microwave current, dc magnetic field and c axis. Attention is focussed on measurements taken with the dc field parallel to the (a, b) planes. In moderate magnetic field, we show that the microwave magnetic response is made up of a vortex motion contribution, which can be described by conventional models, and a noticeable magnetic field induced increase of the quasiparticle density, which exhibits features typical of the existence of lines of nodes in the superconducting gap. We estimate the effective vortex viscosity for vortex motion across the (a, b) planes
c-axis transport and phenomenology of the pseudogap state in Bi2Sr2CaCu2O(8+delta)
No full textWe measure and analyze the resistivity of Bi2Sr 2CaCu2O8+? crystals for different doping ?. We obtain the fraction of carriers ?(T, ?)=n g/ntot that do not participate in the c-axis conductivity. All the curves ?(T, ?) collapse onto a universal curve when plotted against a reduced temperature x=[T-?(?)]/?*(?). We find that at the superconducting transition ng is doping independent. We also show that a magnetic field up to 14 T does not affect the degree of localization in the (a, b) planes but widens the temperature range of the x scaling by suppressing the superconducting phase coherence
- …
