19,379 research outputs found
Pairing State with a time-reversal symmetry breaking in FeAs based superconductors
We investigate the competition between the extended -wave and
-wave pairing order parameters in the iron-based superconductors.
Because of the frustrating pairing interactions among the electron and the hole
fermi pockets, a time reversal symmetry breaking pairing state could be
favored. We analyze this pairing state within the Ginzburg-Landau theory, and
explore the experimental consequences. In such a state, spatial inhomogeneity
induces supercurrent near a non-magnetic impurity and the corners of a square
sample. The resonance mode between the and -wave order
parameters can be detected through the -Raman spectroscopy.Comment: 4 pages, 4 figures, new references adde
Orbital Resonance Mode in Superconducting Iron Pnictides
We show that the fluctuations associated with ferro orbital order in the
and orbitals can develop a sharp resonance mode in the
superconducting state with a nodeless gap on the Fermi surface. This orbital
resonance mode appears below the particle-hole continuum and is analogous to
the magnetic resonance mode found in various unconventional superconductors. If
the pairing symmetry is , a dynamical coupling between the orbital
ordering and the d-wave subdominant pairing channels is present by symmetry.
Therefore the nature of the resonance mode depends on the relative strengths of
the fluctuations in these two channels, which could vary significantly for
different families of the iron based superconductors. The application of our
theory to a recent observation of a new -function-like peak in the
B Raman spectrum of BaKFeAs is discussed.Comment: 6 pages, 3 figure
Replacement Paths via Row Minima of Concise Matrices
Matrix is {\em -concise} if the finite entries of each column of
consist of or less intervals of identical numbers. We give an -time
algorithm to compute the row minima of any -concise matrix.
Our algorithm yields the first -time reductions from the
replacement-paths problem on an -node -edge undirected graph
(respectively, directed acyclic graph) to the single-source shortest-paths
problem on an -node -edge undirected graph (respectively, directed
acyclic graph). That is, we prove that the replacement-paths problem is no
harder than the single-source shortest-paths problem on undirected graphs and
directed acyclic graphs. Moreover, our linear-time reductions lead to the first
-time algorithms for the replacement-paths problem on the following
classes of -node -edge graphs (1) undirected graphs in the word-RAM model
of computation, (2) undirected planar graphs, (3) undirected minor-closed
graphs, and (4) directed acyclic graphs.Comment: 23 pages, 1 table, 9 figures, accepted to SIAM Journal on Discrete
Mathematic
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