Dynamic correlations in the two-channel Kondo model:
a numerical renormalization group study seen against symmetries

Anna Toth  (TU Budapest)


Abstract:
We generalize the spectral sum rule preserving density matrix numerical
renormalization group method (DMNRG) in such a way that it can make use
of an arbitrary number of local compact Lie group symmetries of the
quantum impurity system.  As one of its applications we study the Green's
functions of the highest-weight fields in the electron-hole symmetrical
spin-half two-channel Kondo (2CK) model.  We use a conformal field theory
based scaling approach to predict the analytic properties of the various
Green's functions in the vicinity of the 2CK fixed point and confirm
these predictions by DMNRG calculations.  We compute the universal scaling
curves connecting the 2CK scaling regimes and the channel anisotropy or
magnetic field induced Fermi liquid scaling regimes.  We argue that the
boundaries of the various 2CK scaling regimes depend not only on the type of
the perturbation but also on the operator investigated.  In a small
magnetic field, a universal resonance is observed in the local fermion's
spectral function.  The dominant superconducting instability is found in
the composite superconducting channel.