Regensburg 2004 – scientific programme

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TT: Tiefe Temperaturen

TT 15: Korrelierte Elektronen: Theorie I

TT 15.3: Talk

Tuesday, March 9, 2004, 15:00–15:15, H19

Spectral Densities of Single Impurity Models by Density-Matrix Renormalization — •Götz S. Uhrig¹, Carsten Raas¹, and Frithjof B. Anders² — ¹Institut für Theoretische Physik, Universität zu Köln, Zülpicher Str. 77, 50937 Köln, Germany — ²Institut für Theoretische Physik, Universität Bremen, 28334 Bremen, Germany

The quantitative control of the dynamic correlations of single impurity models is essential in many active fields. We analyze the local propagator with a constant energy resolution by dynamical density-matrix renormalization (D-DMRG). This approach is particularly useful for higher-lying excitations. In contrast to other approaches, sharp dominant resonances at high energies are found. We analyze their line shapes and discuss their origin and importance. An analysis of the Kondo energy scale is also presented.

The D-DMRG provides the density of states convolved with a Lorentzian of width η. Choosing η is a trade-off between run-time and energy resolution. Thus, accurate deconvolution strategies are essential. We analyze several deconvolution methods to calculate continuous spectral densities and propose a novel non-linear algorithm, the least-bias algorithm.

Our findings provide a well-controlled numerical approach to impurity problems which can serve as the impurity solver in dynamical mean field theory (DMFT) calculations as well as in calculations of more complex impurities like quantum dots, molecules, or the effective problems of extended DMFT schemes.