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Complete theoretical understanding of the most complex superconductors requires a detailed knowledge of the symmetry of the superconducting energy-gap $\Delta_\mathbf{k}^\alpha$, for all momenta $\mathbf{k}$ on the Fermi surface of every…

The point contact tunneling technique is used to examine quasiparticle and Josephson currents in overdoped Bi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{8+\delta}$ (Bi-2212) single crystals with bulk T$_{c}$ values near 62 K. High quality…

Superconductivity · Physics 2009-10-31 Lutfi Ozyuzer , John F. Zasadzinski , Chris Kendziora , Kenneth E. Gray

We present a microscopic theory of transport through quantum dot set-ups coupled to superconducting leads. We derive a master equation for the reduced density matrix to lowest order in the tunneling Hamiltonian and focus on quasiparticle…

Mesoscale and Nanoscale Physics · Physics 2013-06-24 Sebastian Pfaller , Andrea Donarini , Milena Grifoni

We present a consistent theory of superconductive tunneling in single-mode junctions within a scattering formulation of Bogoliubov-de Gennes quantum mechanics. Both dc Josephson effect and dc quasiparticle transport in voltage biased…

Superconductivity · Physics 2009-10-28 V. S. Shumeiko , E. N. Bratus' , G. Wendin

We studied the far-infrared reflectance of superconducting MgB2 in and out of equilibrium using pulsed synchrotron radiation. The equilibrium data can be described by a single energy gap at 2 Delta / hc = 43 cm-1. The fit improves slightly…

Superconductivity · Physics 2007-05-23 R. P. S. M. Lobo , J. J. Tu , Eun-Mi Choi , Hyeong-Jin Kim , W. N. Kang , Sung-Ik Lee , G. L. Carr

We develop a theory of tunneling spectroscopy in superconducting topological insulator (STI), i.e. superconducting state of a carrier-doped topological insulator. Based on the quasi-classical approximation, we obtain an analytical…

Superconductivity · Physics 2014-05-16 Shota Takami , Keiji Yada , Ai Yamakage , Masatoshi Sato , Yukio Tanaka

In our tunneling investigation using Andreev superconductor - normal metal - superconductor contacts on LiFeAs single crystals we observed two reproducible independent subharmonic gap structures at dynamic conductance characteristics. From…

Superconductivity · Physics 2012-08-01 S. A. Kuzmichev , T. E. Shanygina , I. V. Morozov , A. I. Boltalin , M. V. Roslova , S. Wurmehl , B. Buchner

Point-contact tunnel junctions using a Au tip on sintered MgB2 pellets reveal a sharp superconducting energy gap that is confirmed by subsequent metallic Sharvin contacts made on the same sample. The peak in the tunneling conductance and…

Superconductivity · Physics 2009-11-07 Herbert Schmidt , J. F. Zasadzinski , K. E. Gray , D. G. Hinks

In this Letter we present new tunneling data on YBa$_2$Cu$_3$O$_7$ thin films by low temperature scanning tunneling spectroscopy. Unusual peak-dip-hump features, previously reported in Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$, are also found in…

Superconductivity · Physics 2009-10-31 T. Cren , D. Roditchev , W. Sacks , J. Klein

The superconducting state is achieved by the condensation of Cooper pairs and is protected by the superconducting gap. The pairing interaction between the two electrons of a Cooper pair determines the superconducting gap function. Thus, it…

The superconducting gap Delta has been measured in Bi2Sr2-xLaxCuO6+d single crystals in a wide range of temperatures 4.2 K < T < Tc by point-contact and tunnelling spectroscopy for current in c-direction. The value of Delta(4.2 K) was found…

We investigate the tunneling conductance of superconductor-insulator-normal metal (SIN) and superconductor-insulator-superconductor (SIS) heterostructures with one superconducting side of the junction that is electrically driven and can…

Superconductivity · Physics 2021-10-18 Maria Teresa Mercaldo , Francesco Giazotto , Mario Cuoco

There is increasing experimental evidence that the superconducting energy gap $\Delta_0$ in the underdoped cuprates is independent of doping concentration $x$ while the superfluid density is linear in $x$. We show that under these…

Superconductivity · Physics 2009-10-30 Patrick A. Lee , Xiao-Gang Wen

Recent experiments indicate that the excitation spectrum of the cuprates is characterised, in the superconducting state, by two energy scales: the ``coherence energy'' \Delta_c and the ``pseudogap'' \Delta_p. Here we consider a simple…

Superconductivity · Physics 2009-11-07 J. Quintanilla , B. L. Gyorffy

Early electron tunneling experiments with the Tl2Ba2CaCu2O8 measured \Delta = 16-28 meV, while bulk optical experiments measured \Delta = 43-45 meV. We report new tunneling measurements of Tl2Ba2CaCu2O8 single crystals and c-axis oriented…

Superconductivity · Physics 2007-05-23 Daniel Mazur , J. F. Zasadzinski , K. E. Gray , Y. C. Ma , N. L. Wang , S. L. Yan

Static and dynamic transport measurements on stacks of intrinsic Josephson junctions on Bi2Sr2CaCu2O8+delta single crystals, near to optimal doping, are presented. The zero bias minimum in dynamic conductance is consistent with a normal…

Superconductivity · Physics 2007-05-23 I. F. G. Parker , M. Endres , P. J. Thomas , G. Yang , A. Yurgens , C. E. Gough

We report on investigations of the superconducting energy gap of the A15 superconductor Nb_3Sn by point-contact spectroscopy of breakjunctions. The voltage-dependent differential conductance dI/dV reveals features of a second energy gap…

Superconductivity · Physics 2015-05-19 M. Marz , W. Goldacker , R. Lortz , G. Goll

We present extensive Scanning Tunneling Spectroscopy (STM/S) measurements at low temperatures in the multiband superconductor MgB$_2$. We find a similar behavior in single crystalline samples and in single grains, which clearly shows the…

Superconductivity · Physics 2009-11-07 P. Martinez-Samper , J. G. Rodrigo , G. Rubio-Bollinger , H. Suderow , S. Vieira , S. Lee , S. Tajima

We report an investigation of the London penetration depth $\Delta\lambda(T)$ on single crystals of the layered superconductor Ta$_4$Pd$_3$Te$_{16}$, where the crystal structure has quasi-one-dimensional characteristics. A linear…

Superconductivity · Physics 2018-01-15 G. M. Pang , M. Smidman , W. H. Jiao , L. Jiao , Z. F. Weng , W. B. Jiang , C. Y. Guo , Y. Chen , G. H. Cao , H. Q. Yuan

The superconducting compound, LiFeAs, is studied by scanning tunneling microscopy and spectroscopy. A gap map of the unreconstructed surface indicates a high degree of homogeneity in this system. Spectra at 2 K show two nodeless…

Superconductivity · Physics 2012-10-17 Shun Chi , S. Grothe , Ruixing Liang , P. Dosanjh , W. N. Hardy , S. A. Burke , D. A. Bonn , Y. Pennec