2,032 research outputs found
Franck-Condon Factors as Spectral Probes of Polaron Structure
We apply the Merrifield variational method to the Holstein molecular crystal
model in D dimensions to compute non-adiabatic polaron band energies and
Franck-Condon factors at general crystal momenta. We analyze these observable
properties to extract characteristic features related to polaron self-trapping
and potential experimental signatures. These results are combined with others
obtained by the Global-Local variational method in 1D to construct a polaron
phase diagram encompassing all degrees of adiabaticity and all electron-phonon
coupling strengths. The polaron phase diagram so constructed includes disjoint
regimes occupied by "small" polarons, "large" polarons, and a newly-defined
class of "compact" polarons, all mutually separated by an intermediate regime
occupied by transitional structures
Rearrangement collisions between gold clusters
Collision processes between two gold clusters are investigated using
classical molecular dynamics in combination with embedded atom (EA) potentials,
after checking the reliability of EA results by contrasting them with first
principles calculations. The Au projectiles considered are both single atoms
(N=1) and clusters of N=2, 12, 13 and 14 atoms. The targets contain N= 12, 13
and 14 gold atoms. The initial projectile energy E is in the range 0 < E < 1.5
eV/atom. The results of the collision processes are described and analyzed in
detail.Comment: LATeX file, 8 figures, uses svjour.cl
On the Generalized Kramers Problem with Oscillatory Memory Friction
The time-dependent transmission coefficient for the Kramers problem exhibits
different behaviors in different parameter regimes. In the high friction regime
it decays monotonically ("non-adiabatic"), and in the low friction regime it
decays in an oscillatory fashion ("energy-diffusion-limited"). The generalized
Kramers problem with an exponential memory friction exhibits an additional
oscillatory behavior in the high friction regime ("caging"). In this paper we
consider an oscillatory memory kernel, which can be associated with a model in
which the reaction coordinate is linearly coupled to a nonreactive coordinate,
which is in turn coupled to a heat bath. We recover the non-adiabatic and
energy-diffusion-limited behaviors of the transmission coefficient in
appropriate parameter regimes, and find that caging is not observed with an
oscillatory memory kernel. Most interestingly, we identify a new regime in
which the time-dependent transmission coefficient decays via a series of rather
sharp steps followed by plateaus ("stair-like"). We explain this regime and its
dependence on the various parameters of the system
Proximity-induced topological transition and strain-induced charge transfer in graphene/MoS2 bilayer heterostructures
Graphene/MoS2 heterostructures are formed by combining the nanosheets of
graphene and monolayer MoS2. The electronic features of both constituent
monolayers are rather well-preserved in the resultant heterostructure due to
the weak van der Waals interaction between the layers. However, the proximity
of MoS2 induces strong spin orbit coupling effect of strength ~1 meV in
graphene, which is nearly three orders of magnitude larger than the intrinsic
spin orbit coupling of pristine graphene. This opens a bandgap in graphene and
further causes anticrossings of the spin-nondegenerate bands near the Dirac
point. Lattice incommensurate graphene/MoS2 heterostructure exhibits
interesting moire' patterns which have been observed in experiments. The
electronic bandstructure of heterostructure is very sensitive to biaxial strain
and interlayer twist. Although the Dirac cone of graphene remains intact and no
charge-transfer between graphene and MoS2 layers occurs at ambient conditions,
a strain-induced charge-transfer can be realized in graphene/MoS2
heterostructure. Application of a gate voltage reveals the occurrence of a
topological phase transition in graphene/MoS2 heterostructure. In this chapter,
we discuss the crystal structure, interlayer effects, electronic structure,
spin states, and effects due to strain and substrate proximity on the
electronic properties of graphene/MoS2 heterostructure. We further present an
overview of the distinct topological quantum phases of graphene/MoS2
heterostructure and review the recent advancements in this field.Comment: 31 pages, 12 figure
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