Metal-Insulator Transition in Disordered Two-Dimensional Electron Systems

We present a theory of the metal-insulator transition in a disordered two-dimensional electron gas. A quantum critical point, separating the metallic phase which is stabilized by electronic interactions, from the insulating phase where disorder prevails over the electronic interactions, has been identified. The existence of the quantum critical point leads to a divergence in the density of states of the underlying collective modes at the transition, causing the thermodynamic properties to behave critically as the transition is approached. We show that the interplay of electron-electron interactions and disorder can explain the observed transport properties and the anomalous enhancement of the spin susceptibility near the metal-insulator transition

Broken Symmetry and Coherence of Molecular Vibrations in Tunnel Transitions

We examine the Breit-Wigner resonances that ensue from field effects in molecular single electron transistors (SETs). The adiabatic dynamics of a quantum dot elastically attached to electrodes are treated in the Born-Oppenheimer approach. The relation between thermal and shot noise induced by the source-drain voltage $V_{bias}$ is found when the SET operates in a regime tending to thermodynamic equilibrium far from resonance. The equilibration of electron-phonon subsystems produces broadening and doublet splitting of transparency resonances helping to explain a negative differential resistance (NDR)of current versus voltage (I-V) curves. Mismatch between the electron and phonon temperatures brings out the bouncing-ball mode in the crossover regime close to the internal vibrations mode. The shuttle mechanism occurs at a threshold $V_{bias}$ of the order of the Coulomb energy $U_c$. An accumulation of charge is followed by the Coulomb blockade and broken symmetry of a single or double well potential. The Landau bifurcation cures the shuttling instability and the resonance levels of the quantum dot become split because of molecular tunneling. We calculate the tunnel gaps of conductivity and propose a tunneling optical trap (TOT) for quantum dot isolation permitting coherent molecular tunneling by virtue of Josephson oscillations in a charged Bose gas. We discuss experimental conditions when the above theory can be tested.Comment: 45 pages, 18 figures; The talk presented at Workshop "Decoherence, Entanglement and Information Protection in Complex Quantum Systems", Les Houches, April 25 -30, 2004. Corrected typos and minor grammatical and stylistic changes; Editors: V. M. Akulin, A. Sarfati, G. Kurizki and S. Pellegrin Publisher: Kluwer Academic Publisher, Boston / Dordrecht / London: to appear in 2005 (February / March

The lobster and the maid: scenario-dependence and reader manipulation in Agatha Christie

Readers of detective fiction deliberately seek to be deceived by the stories they read; in this manner, the genre forms a series of texts that aim to manipulate and persuade. This paper describes Agatha Christie’s manipulation of plot-significant information in her short story 'The Tuesday Night Club' by discussing a reader’s psychological depth of processing of significant entities and characters. In particular, I describe this technique within cognitive stylistics using the theory of scenario-dependence, in which a reader’s partitions of memory dictate the focus of a scenario and the role­ mapping of entities within a narrative. In this manner, the paper describes how Christie’s puzzle-like plot invites a reader’s engagement while she simultaneously uses psychological means to divert reader scrutiny and persuade them to follow the wrong ‘path’ to the story’s conclusion. This paper is part of a wider project to describe the cognitive and stylistic basis of reader manipulation in detective fiction (see also Alexander 2006)

Photon echoes of molecular photoassociation

Revivals of optical coherence of molecular photoassociation driven by two ultrashort laser pulses are addressed in the Condon approach. Based on textbook examples and numerical simulation of KrF excimer molecules, a prediction is made about an existence of photon echo on free-bound transitions. Delayed rise and fall of nonlinear polarization in the half-collisions are to be resulted from the resonant quantum states interference whether it be in gas, liquid or solid phases.Comment: 15 pages and 5 figures presented at ICONO '98'(Moscow, 1998): Fundamental Aspects of Laser-Matter Interaction, New Nonlinear Optical Materials and Physics of Low-Dimensional Structure