Tunneling into the normal state of Pr(2-x)CexCuO4

The temperature dependence of the tunneling conductance was measured for various doping levels of Pr(2-x)CexCuO4 using planar junctions. A normal state gap is seen at all doping levels studied, x=0.11 to x=0.19. We find it to vanish above a certain temperature T*. T* is greater than Tc for the underdoped region and it follows Tc on the overdoped side. This behavior suggests finite pairing amplitude above Tc on the underdoped side

Remarkable change of tunneling conductance in YBCO films in fields up to 32.4T

We studied the tunneling density of states in YBCO films under strong currents flowing along node directions. The currents were induced by fields of up to 32.4T parallel to the film surface and perpendicular to the $CuO_{2}$ planes. We observed a remarkable change in the tunneling conductance at high fields where the gap-like feature shifts discontinuously from 15meV to a lower bias of 11meV, becoming more pronounced as the field increases. The effect takes place in increasing fields around 9T and the transition back to the initial state occurs around 5T in decreasing fields. We argue that this transition is driven by surface currents induced by the applied magnetic field.Comment: 4 pages, 7 figure

Factor Graphs for Heterogeneous Bayesian Decentralized Data Fusion

This paper explores the use of factor graphs as an inference and analysis tool for Bayesian peer-to-peer decentralized data fusion. We propose a framework by which agents can each use local factor graphs to represent relevant partitions of a complex global joint probability distribution, thus allowing them to avoid reasoning over the entirety of a more complex model and saving communication as well as computation cost. This allows heterogeneous multi-robot systems to cooperate on a variety of real world, task oriented missions, where scalability and modularity are key. To develop the initial theory and analyze the limits of this approach, we focus our attention on static linear Gaussian systems in tree-structured networks and use Channel Filters (also represented by factor graphs) to explicitly track common information. We discuss how this representation can be used to describe various multi-robot applications and to design and analyze new heterogeneous data fusion algorithms. We validate our method in simulations of a multi-agent multi-target tracking and cooperative multi-agent mapping problems, and discuss the computation and communication gains of this approach.Comment: 8 pages, 6 figures, 1 table, submitted to the 24th International Conference on Information Fusio

Role of oxygen in the electron-doped superconducting cuprates

We report on resistivity and Hall measurements in thin films of the electron-doped superconducting cuprate Pr$_{2-x}$Ce$_{x}$CuO$_{4\pm\delta}$. Comparisons between x = 0.17 samples subjected to either ion-irradiation or oxygenation demonstrate that changing the oxygen content has two separable effects: 1) a doping effect similar to that of cerium, and 2) a disorder effect. These results are consistent with prior speculations that apical oxygen removal is necessary to achieve superconductivity in this compound.Comment: 5 pages, 5 figure

Infrared Signature of the Superconducting State in Pr(2-x)Ce(x)CuO(4)

We measured the far infrared reflectivity of two superconducting Pr(2-x)Ce(x)CuO(4) films above and below Tc. The reflectivity in the superconducting state increases and the optical conductivity drops at low energies, in agreement with the opening of a (possibly) anisotropic superconducting gap. The maximum energy of the gap scales roughly with Tc as 2 Delta_{max} / kB Tc ~ 4.7. We determined absolute values of the penetration depth at 5 K as lambda_{ab} = (3300 +/- 700) A for x = 0.15 and lambda_{ab} = (2000 +/- 300) A for x = 0.17. A spectral weight analysis shows that the Ferrell-Glover-Tinkham sum rule is satisfied at conventional low energy scales \~ 4 Delta_{max}.Comment: 4 pages, 4 figure