1201.5610 (Chung-Hou Chung et al.)

Quantum criticality in Kondo quantum dot coupled to 2D topological
insulator    [PDF]

Chung-Hou Chung, Salman Silotri

We investigate theoretically the quantum phase transition between the
one-channel Kondo (1CK) and two-channel Kondo (2CK) fixed points in a quantum
dot coupled to edge states of interacting 2D topological insulators (2DTI) with
Luttinger parameter $0mapped onto an anisotropic two-channel Kondo model via bosonization. For $K<1$,
the strong coupling 2CK fixed point was argued to be stable for infinitesimally
weak tunnelings between dot and the 2DTI based on the simple scaling
dimensional analysis in Ref. 16. We re-examine the model beyond the scaling
dimension analysis via a 1-loop renormalization group (RG) approach on the
effective Kondo model via re-fermionization near the 2CK fixed point. We find
for $K<1$ the 2CK fixed point can be unstable towards the 1CK fixed point and
the system may undergo a quantum phase transition (QPT) between 1CK and 2CK
fixed points. The QPT in our model comes as a result of the combined Kondo and
the helical Luttinger physics in 2DTI, and it serves as the first example of
the 1CK-2CK QPT that is accessible by the perturbative RG approach. We extract
quantum critical and crossover behaviors from various thermodynamical
quantities near the quantum critical point.

View original: http://arxiv.org/abs/1201.5610