5,812 research outputs found
Vibrating Superconducting Island in a Josephson Junction
We consider a combined nanomechanical-supercondcuting device that allows the
Cooper pair tunneling to interfere with the mechanical motion of the middle
superconducting island. Coupling of mechanical oscillations of a
superconducting island between two superconducting leads to the electronic
tunneling generate a supercurrent which is modulated by the oscillatory motion
of the island. This coupling produces alternating finite and vanishing
supercurrent as function of the superconducting phases. Current peaks are
sensitive to the superconducting phase shifts relative to each other. The
proposed device may be used to study the nanoelectromechanical coupling in case
of superconducting electronics.Comment: 4 pages, 3 figures, to appear in Phys. Rev. Let
Vibrational coherence in electron spin resonance in nanoscale oscillators
We study a scheme for electrical detection, using electron spin resonance, of
coherent vibrations in a molecular single electron level trapped near a
conduction channel. Both equilibrium spin-currents and non-equilibrium spin-
and charge currents are investigated. Inelastic side-band anti-resonances
corresponding to the vibrational modes appear in the electron spin resonance
spectrum.Comment: 4 pages, 3 figures: Published versio
Continuous quantum phase transition in a Kondo lattice model
We study the magnetic quantum phase transition in an anisotropic Kondo
lattice model. The dynamical competition between the RKKY and Kondo
interactions is treated using an extended dynamic mean field theory (EDMFT)
appropriate for both the antiferromagnetic and paramagnetic phases. A quantum
Monte Carlo approach is used, which is able to reach very low temperatures, of
the order of 1% of the bare Kondo scale. We find that the finite-temperature
magnetic transition, which occurs for sufficiently large RKKY interactions, is
first order. The extrapolated zero-temperature magnetic transition, on the
other hand, is continuous and locally critical.Comment: 4 pages, 4 figures; updated, to appear in PR
Phase diagram of doped BaFeAs superconductor under broken symmetry
We develop a minimal multiorbital tight-binding model with realistic hopping
parameters. The model breaks the symmetry of the tetragonal point group by
lowering it from to , which accurately describes the Fermi
surface evolution of the electron-doped BaFeCoAs and hole-doped
BaKFeAs compounds. An investigation of the phase diagram
with a mean-field -- Bogoliubov-de Gennes Hamiltonian results in
agreement with the experimentally observed electron- and hole-doped phase
diagram with only one set of , and parameters. Additionally, the
self-consistently calculated superconducting order parameter exhibits
-wave pairing symmetry with a small d-wave pairing admixture in the
entire doping range, % The superconducting -wave order parameter
which is the subtle result of the weakly broken symmetry and competing
interactions in the multiorbital mean-field Hamiltonian
Imaging the formation of high-energy dispersion anomalies in the actinide UCoGa
We use angle-resolved photoemission spectroscopy (ARPES) to image the
emergence of substaintial dispersion anomalies in the electronic
renormalization of the actinide compound UCoGa which was presumed to belong
to a conventional Fermi liquid family. Kinks or abrupt breaks in the slope of
the quasiparticle dispersion are detected both at low (130 meV) and high
(1 eV) binding energies below the Fermi energy, ruling out any
significant contribution of phonons. We perform numerical calculations to
demonstrate that the anomalies are adequately described by coupling between
itinerant fermions and spin fluctuations arising from the particle-hole
continuum of the spin-orbit split states of uranium. These anomalies are
resemble the `waterfall' phenomenon of the high-temperature copper-oxide
superconductors, suggesting that spin fluctuations are a generic route toward
multiform electronic phases in correlated materials as different as
high-temperature superconductors and actinides.Comment: 10 pages including supplementary material, Accepted for publication
in PR
Theory of ultrafast quasiparticle dynamics in high-temperature superconductors: Pump fluence dependence
We present a theory for the time-resolved optical spectroscopy of
high-temperature superconductors at high excitation densities with strongly
anisotropic electron-phonon coupling. A signature of the strong coupling
between the out-of-plane, out-of-phase O buckling mode () and
electronic states near the antinode is observed as a higher-energy peak in the
time-resolved optical conductivity and Raman spectra, while no evidence of the
strong coupling between the in-plane Cu-O breathing mode and nodal electronic
states is observed. More interestingly, it is observed that under appropriate
conditions of pump fluence, this signature exhibits a re-entrant behavior with
time delay, following the fate of the superconducting condensate.Comment: 5 pages, 3 embedded eps figures, to appear in PR
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