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TT: Tiefe Temperaturen

TT 6: Postersitzung I: Josephsonkontakte und SQUIDs, Supraleitung: Theorie, Korrelierte Elektronen, Niederdimensionale Systeme, Magnetotransport, Quantenhalleffekt, Kohlenstoff-Nanoröhrchen, Quantenflüssigkeiten

TT 6.16: Poster

Monday, March 26, 2001, 14:30–17:00, Rang S\ 3

Generalized Numerical Renormalization Group for dynamical quantities — •Walter Hofstetter — Theoretische Physik III, Universität Augsburg, 86135 Augsburg

We introduce a new approach (the DM–NRG) for calculating dynamical properties within the Numerical Renormalization Group. It is demonstrated that the method previously used fails for the Anderson impurity in a magnetic field due to the absence of energy scale separation. The problem is solved by evaluating the Green’s function with respect to the reduced density matrix of the full system, which leads to accurate spectra in agreement with the sum rule for the static magnetization. In particular, the strong effect of an external perturbation on the symmetry of the ground state is correctly assessed by the DM–NRG. The new procedure provides a unifying framework for calculating dynamics at any temperature and represents the correct extension of Wilson’s original thermodynamic calculation. It will be relevant for future studies of more complex impurities.

[1] W. Hofstetter, Phys. Rev. Lett. 85, 1508 (2000).