We present results of a microwave surface impedance study of the heavy fermion superconductor UBe(13). We clearly observe an absorption peak whose frequency and temperature dependence scales with the BCS gap function Delta(T). Resonant absorption into a collective mode, with energy approximately proportional to the superconducting gap, is proposed as a possible explanation. Fits to the data pro...

Received DOI: 2 Superconductivity arises when solids have conducting bands (singly occupied wave functions) that do not have electron-nuclear scattering (Fermi contact) and the temperature is low enough to eliminate partial wave scattering of electrons. This means that the conducting bands do not include s basis functions (atomic quantum numbers l ,m = 0), and the temperature is low enough so t...

Superconducting point contacts have been used for measuring magnetic polarizations, identifying magnetic impurities, electronic structures, and even the vibrational modes of small molecules. Due to intrinsically small energy scale in the subgap structures of the supercurrent determined by the size of the superconducting energy gap, superconductors provide ultrahigh sensitivities for high resolu...

The paper compares the K-dependence of the superconducting gap in different doping ranges. The fine behavior of the leading edge gap indicates that the pairing susceptibility is peaked at special regions on the Fermi surface. These hot regions are found to be centered away from nominal " hot spots ". This behavior is attributed to a feedback effect on the pairing boson. Identification is made t...

We experimentally demonstrate the in situ tunability of the minimum energy splitting (gap) of a superconducting flux qubit by means of an additional flux loop. Pulses applied via a local control line allow us to tune the gap over a range of several GHz on a nanosecond time scale. The strong flux sensitivity of the gap (up to approximately 0.7 GHz/mPhi0) opens up the possibility to create differ...

Although neutrons do not couple directly to the superconducting order parameter, they have nevertheless played an important role in advancing our understanding of the pairing mechanism and the symmetry of the superconducting energy gap in the iron arsenide compounds. Measurements of the spin and lattice dynamics have been performed on non-superconducting ‘parent’ compounds based on the LaFeAsO ...

We study tunneling spectroscopy between a normal metal and an underdoped cuprate superconductor modeled by a phenomenological theory in which the pseudogap is a precursor to the undoped Mott insulator. In the low barrier tunneling limit, the spectra are enhanced by Andreev reflection only within a voltage region of the small superconducting energy gap. In the high barrier tunneling limit, the s...

We have observed back-bending structures at high bias current in the current-voltage curves of intrinsic Josephson junctions. These structures may be caused by nonequilibrium quasiparticle injection and/or Joule heating. The energy gap suppression varies considerably with temperature. Different levels of the suppression are observed when the same level of current passes through top electrodes o...

We present studies of the photoexcited quasiparticle dynamics in Tl2Ba2Ca2Cu3Oy (Tl-2223) using femtosecond optical techniques. Deep into the superconducting state (below 40 K), a dramatic change occurs in the temporal dynamics associated with photoexcited quasiparticles rejoining the condensate. This is suggestive of entry into a coexistence phase which, as our analysis reveals, opens a gap in...

The single rung t-J ladder is analyzed in a mean field theory using Gutzwiller renormalization of the matrix elements to account for strong correlation. The spin liquid (RVB) state at half-filling evolves into a superconducting state upon doping. The order parameter has a modified d-wave character. A lattice of weakly coupled ladders should show a superconducting phase transition. PACS: 71.27.+...