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Dissipative Effects on Quantum Sticking

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 Added by Dennis Clougherty
 Publication date 2010
  fields Physics
and research's language is English




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Using variational mean-field theory, many-body dissipative effects on the threshold law for quantum sticking and reflection of neutral and charged particles are examined. For the case of an ohmic bosonic bath, we study the effects of the infrared divergence on the probability of sticking and obtain a non-perturbative expression for the sticking rate. We find that for weak dissipative coupling $alpha$, the low energy threshold laws for quantum sticking are modified by an infrared singularity in the bath. The sticking probability for a neutral particle with incident energy $Eto 0$ behaves asymptotically as ${it s}sim E^{(1+alpha)/2(1-alpha)}$; for a charged particle, we obtain ${it s}sim E^{alpha/2(1-alpha)}$. Thus, quantum mirrors --surfaces that become perfectly reflective to particles with incident energies asymptotically approaching zero-- can also exist for charged particles.



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The probability that a particle will stick to a surface is fundamental to a variety of processes in surface science, including catalysis, epitaxial growth, and corrosion. At ultralow energies, how particles scatter or stick to a surface affects the performance of atomic clocks, matter-wave interferometers, atom chips and other quantum information processing devices. In this energy regime, the sticking probability is influenced by a distinctly quantum mechanical effect: quantum reflection, a result of matter wave coherence, suppresses the probability of finding the particle near the surface and reduces the sticking probability. We find that another quantum effect can occur, further shaping the sticking probability: the orthogonality catastrophe, a result of the change in the quantum ground state of the surface in the presence of a particle, can dramatically alter the probability for quantum sticking and create a superreflective surface at low energies.
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A continuum model for low-energy physisorption on a membrane under tension is proposed and studied with variational mean-field theory. A discontinuous change in the energy-dependent sticking coefficient is predicted under certain conditions. This singularity is a result of the bosonic orthogonality catastrophe of the vibrational states of the membrane. The energy-dependent sticking coefficient is predicted to have exponential scaling in 1/E above the singularity. The application of this model to the quantum sticking of cold hydrogen to suspended graphene is discussed. The model predicts that a beam of atomic hydrogen can be completely reflected by suspended graphene at ultralow energies.
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