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Valley-resolved electronic coherences in silicon observed by attosecond transient absorption spectroscopy
Electronic coherences are observed in silicon by attosecond transient absorption spectroscopy. Various sub-4 fs oscillations across the conduction band reveal complex couplings between valence-conduction and conduction-conduction bands indicating pathways for coherent preparation of highly excited electrons
Thermal Conduction and Multiphase Gas in Cluster Cores
We examine the role of thermal conduction and magnetic fields in cores of
galaxy clusters through global simulations of the intracluster medium (ICM). In
particular, we study the influence of thermal conduction, both isotropic and
anisotropic, on the condensation of multiphase gas in cluster cores. Previous
hydrodynamic simulations have shown that cold gas condenses out of the hot ICM
in thermal balance only when the ratio of the cooling time () and
the free-fall time () is less than . Since thermal
conduction is significant in the ICM and it suppresses local cooling at small
scales, it is imperative to include thermal conduction in such studies. We find
that anisotropic (along local magnetic field lines) thermal conduction does not
influence the condensation criterion for a general magnetic geometry, even if
thermal conductivity is large. However, with isotropic thermal conduction cold
gas condenses only if conduction is suppressed (by a factor )
with respect to the Spitzer value.Comment: 7 pages, 4 figures; replaced by the MNRAS-accepted versio
Entanglement of an impurity and conduction spins in the Kondo model
Based on Yosida's ground state of the single-impurity Kondo Hamiltonian, we
study three kinds of entanglement between an impurity and conduction electron
spins. First, it is shown that the impurity spin is maximally entangled with
all the conduction electrons. Second, a two-spin density matrix of the impurity
spin and one conduction electron spin is given by a Werner state. We find that
the impurity spin is not entangled with one conduction electron spin even
within the Kondo screening length , although there is the spin-spin
correlation between them. Third, we show the density matrix of two conduction
electron spins is nearly same to that of a free electron gas. The single
impurity does not change the entanglement structure of the conduction electrons
in contrast to the dramatic change in electrical resistance.Comment: 5 pages, 2 figures, accepted for publication in Physical Review
Quantum -core conduction on the Bethe lattice
Classical and quantum conduction on a bond-diluted Bethe lattice is
considered. The bond dilution is subject to the constraint that every occupied
bond must have at least neighboring occupied bonds, i.e. -core
diluted. In the classical case, we find the onset of conduction for is
continuous, while for , the onset of conduction is discontinuous with the
geometric random first-order phase transition driving the conduction
transition. In the quantum case, treating each occupied bond as a random
scatterer, we find for that the random first-order phase transition in
the geometry also drives the onset of quantum conduction giving rise to a new
universality class of Anderson localization transitions.Comment: 12 pgs., 6 fig
Kondo Effect in a Metal with Correlated Conduction Electrons: Diagrammatic Approach
We study the low-temperature behavior of a magnetic impurity which is weakly
coupled to correlated conduction electrons. To account for conduction electron
interactions a diagrammatic approach in the frame of the 1/N expansion is
developed. The method allows us to study various consequences of the conduction
electron correlations for the ground state and the low-energy excitations. We
analyse the characteristic energy scale in the limit of weak conduction
electron interactions. Results are reported for static properties (impurity
valence, charge susceptibility, magnetic susceptibility, and specific heat) in
the low-temperature limit.Comment: 16 pages, 9 figure
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