Boundary quantum criticality in models of magnetic impurities coupled to bosonic baths
- Institut Neel, CNRS and Universite Joseph Fourier, Boite Postale 166, 38042 Grenoble (France)
- Institut fuer Theoretische Physik, Universitaet zu Koeln, Zuelpicher Strasse 77, 50937 Cologne (Germany)
We investigate quantum impurity problems, where a local magnetic moment is coupled to the spin density of a bosonic environment, leading to bosonic versions of the standard Kondo and Anderson impurity models. In a physical situation, these bosonic environments can correspond either to deconfined spinons in certain classes of Z{sub 2} frustrated antiferromagnets, or to particles in a multicomponent Bose gase (in which case the spin degree of freedom is attributed to hyperfine levels). Using renormalization group techniques, we establish that our impurity models, which feature an exchange interaction analogous to Kondo impurities in Fermi liquids, allow flow toward a stable strong-coupling state. Since the low-energy bosons exist around a single point in momentum space, and there is no Fermi surface, an impurity quantum phase transition occurs at intermediate coupling, separating screened and unscreened phases. This behavior is qualitatively different from previously studied spin-isotropic variants of the spin-boson model, which display stable intermediate-coupling fixed points and no screening.
- OSTI ID:
- 20951534
- Journal Information:
- Physical Review. B, Condensed Matter and Materials Physics, Vol. 75, Issue 22; Other Information: DOI: 10.1103/PhysRevB.75.224420; (c) 2007 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 1098-0121
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
SUPERCONDUCTIVITY AND SUPERFLUIDITY
36 MATERIALS SCIENCE
ANTIFERROMAGNETISM
BOSONS
CRITICALITY
DEGREES OF FREEDOM
DENSITY
EXCHANGE INTERACTIONS
FERMI GAS
FERMI LEVEL
GALLIUM SELENIDES
IMPURITIES
INTERMEDIATE COUPLING
MAGNETIC MOMENTS
PHASE TRANSFORMATIONS
RENORMALIZATION
SPIN
STRONG-COUPLING MODEL