Regular and singular Fermi-liquid fixed points in quantum impurity models

Pankaj Mehta, Natan Andrei, P. Coleman, L. Borda, and Gergely Zarand
Phys. Rev. B 72, 014430 – Published 14 July 2005

Abstract

We show that the traditional classification of quantum inpurity models based on thermodynamics is insufficient to probe the nature of their low-energy dynamics. We propose an analysis based on scattering theory, dividing Fermi liquids into regular Fermi liquids and singular Fermi liquids. In both cases electrons at the Fermi energy scatter elastically off the impurity, but in the case of regular Fermi liquids the scattering has analytical properties in the vicinity of the Fermi energy, while for singular Fermi liquids it does not, resulting in a breakdown of Nozières’ Fermi-liquid picture and singular thermodynamic behavior. Using the Bethe ansatz and numerical renormalization group, we show that the ordinary Kondo model is a regular Fermi liquid whereas the underscreened Kondo model is a a singular Fermi liquid. Conventional regular Fermi liquid behavior is reestablished in an external magnetic field H, but with a density of states which diverges as 1H. Our results may be relevant for the recently observed field-tuned quantum criticality in heavy electron materials.

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  • Received 14 April 2004

DOI:https://doi.org/10.1103/PhysRevB.72.014430

©2005 American Physical Society

Authors & Affiliations

Pankaj Mehta, Natan Andrei, and P. Coleman

  • Center for Materials Theory, Rutgers University, Piscataway, New Jersey 08855, USA

L. Borda

  • Sektion Physik and Center for Nanoscience, LMU München, Theresienstrasse 37, 80333 München, Germany and Hungarian Academy of Sciences, Institute of Physics, TU Budapest, H-1521, Hungary

Gergely Zarand

  • Theoretical Physics Department, Budapest University of Technology and Economics, Budafoki ut 8. H-1521 Hungary

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Vol. 72, Iss. 1 — 1 July 2005

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