6,419 research outputs found
Kondo effect in transport through molecules adsorbed on metal surfaces: from Fano dips to Kondo peaks
The Kondo effect observed in recent STM experiments on transport through CoPc
and TBrPP-Co molecules adsorbed on Au(111) and Cu(111) surfaces, respectively,
is discussed within the framework of a simple model (Phys. Rev. Lett. {\bf 97},
076806 (2006)). It is shown that, in the Kondo regime and by varying the
adequate model parameters, it is possible to produce a crossover from a
conductance Kondo peak (CoPc) to a conductance Fano dip (TBrPP-Co). In the case
of TBrPP-Co/Cu(111) we show that the model reproduces the changes in the shape
of the Fano dip, the raising of the Kondo temperature and shifting to higher
energies of the dip minimum when the number of nearest neighbors molecules is
lowered. These features are in line with experimental observations indicating
that our simple model contains the essential physics underlying the transport
properties of such complex molecules.Comment: 4 pages, 3 figures, submitted to PR
Quantum Analogy of Poisson Geometry, Related Dendriform Algebras and Rota-Baxter Operators
We will introduce an associative (or quantum) version of Poisson structure
tensors. This object is defined as an operator satisfying a "generalized"
Rota-Baxter identity of weight zero. Such operators are called generalized
Rota-Baxter operators. We will show that generalized Rota-Baxter operators are
characterized by a cocycle condition so that Poisson structures are so. By
analogy with twisted Poisson structures, we propose a new operator "twisted
Rota-Baxter operators" which is a natural generalization of generalized
Rota-Baxter operators. It is known that classical Rota-Baxter operators are
closely related with dendriform algebras. We will show that twisted Rota-Baxter
operators induce NS-algebras which is a twisted version of dendriform algebra.
The twisted Poisson condition is considered as a Maurer-Cartan equation up to
homotopy. We will show the twisted Rota-Baxter condition also is so. And we
will study a Poisson-geometric reason, how the twisted Rota-Baxter condition
arises.Comment: 18 pages. Final versio
Energy transfer dynamics and thermalization of two oscillators interacting via chaos
We consider the classical dynamics of two particles moving in harmonic
potential wells and interacting with the same external environment (HE),
consisting of N non-interacting chaotic systems. The parameters are set so that
when either particle is separately placed in contact with the environment, a
dissipative behavior is observed. When both particles are simultaneously in
contact with HE an indirect coupling between them is observed only if the
particles are in near resonance. We study the equilibrium properties of the
system considering ensemble averages for the case N=1 and single trajectory
dynamics for N large. In both cases, the particles and the environment reach an
equilibrium configuration at long times, but only for large N a temperature can
be assigned to the system.Comment: 8 pages, 6 figure
Critical behavior at Mott-Anderson transition: a TMT-DMFT perspective
We present a detailed analysis of the critical behavior close to the
Mott-Anderson transition. Our findings are based on a combination of numerical
and analytical results obtained within the framework of Typical-Medium Theory
(TMT-DMFT) - the simplest extension of dynamical mean field theory (DMFT)
capable of incorporating Anderson localization effects. By making use of
previous scaling studies of Anderson impurity models close to the
metal-insulator transition, we solve this problem analytically and reveal the
dependence of the critical behavior on the particle-hole symmetry. Our main
result is that, for sufficiently strong disorder, the Mott-Anderson transition
is characterized by a precisely defined two-fluid behavior, in which only a
fraction of the electrons undergo a "site selective" Mott localization; the
rest become Anderson-localized quasiparticles.Comment: 4+ pages, 4 figures, v2: minor changes, accepted for publication in
Phys. Rev. Let
Comment on the Adiabatic Condition
The experimental observation of effects due to Berry's phase in quantum
systems is certainly one of the most impressive demonstrations of the
correctness of the superposition principle in quantum mechanics. Since Berry's
original paper in 1984, the spin 1/2 coupled with rotating external magnetic
field has been one of the most studied models where those phases appear. We
also consider a special case of this soluble model. A detailed analysis of the
coupled differential equations and comparison with exact results teach us why
the usual procedure (of neglecting nondiagonal terms) is mathematically sound.Comment: 9 page
Non universality of entanglement convertibility
Recently, it has been suggested that operational properties connected to
quantum computation can be alternative indicators of quantum phase transitions.
In this work we systematically study these operational properties in 1D systems
that present phase transitions of different orders. For this purpose, we
evaluate the local convertibility between bipartite ground states. Our results
suggest that the operational properties, related to non-analyticities of the
entanglement spectrum, are good detectors of explicit symmetries of the model,
but not necessarily of phase transitions. We also show that thermodynamically
equivalent phases, such as Luttinger liquids, may display different
convertibility properties depending on the underlying microscopic model.Comment: 5 pages + references, 4 figures - improved versio
Using the Sound Card as a Timer
Experiments in mechanics can often be timed by the sounds they produce. In
such cases, digital audio recordings provide a simple way of measuring time
intervals with an accuracy comparable to that of photogate timers. We
illustrate this with an experiment in the physics of sports: to measure the
speed of a hard-kicked soccer ball.Comment: 3 pages, 4 figures, Late
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