Dresden 2009 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 35: Postersession Transport: Nanoelectronics, Quantum Coherence and Quantum Information, Fluctuations and Noise

TT 35.13: Poster

Mittwoch, 25. März 2009, 14:00–18:00, P1A

Fermi-edge singularities: Bulk vs. mesoscopic systems — •Martina Hentschel and Georg Röder — MPI für Physik komplexer Systeme, Dresden

Fermi-edge singularities are among the simplest many-body effects and have been a key interest in condensed matter physics for many years. They have been extensively studied, and are understood, for bulk systems such as metals. In contrast, our focus here is on small (mesoscopic) systems like quantum dots and graphene. We mainly address the Fermi-edge singularities in the photoabsorption cross section that are known as the x-ray edge problem. They comprise the phenomena of Anderson orthogonality catastrophe and Mahan's exciton (Mahan-Nozieres-DeDominicis response) and result from the system's many-body response to the sudden, localized perturbation given by the core hole that is left behind when the x-ray excites an electron. We show that the mesoscopic regime holds surprises in form of many-body responses that strongly deviate from the macroscopic (bulk, or metallic) case. The differences originate in the finite system size, the intrinsic mesoscopic fluctuations, and most importantly, the modifications of the electron dynamics in confined ballistic systems that are typically studied in the field of quantum chaos. A particularly interesting behavior is seen in graphene where the vanishing density of states at the Dirac point significantly modifies the system's many-body response.