標題: Quantum criticality in a Kondo quantum dot coupled to helical edge states of interacting 2D topological insulators
作者: Chung, Chung-Hou
Silotri, Salman
電子物理學系
Department of Electrophysics
關鍵字: Kondo effect;quantum criticality;quantum dot;topological insulators
公開日期: 9-一月-2015
摘要: We investigate theoretically the quantum phase transition (QPT) between the one-channel Kondo (ICK) and two-channel Kondo (2CK) fixed points in a quantum dot coupled to helical edge states of interacting 2D topological insulators (2DTI) with Luttinger parameter 0 < K < 1. The model was studied by Law et al (2010 Phys. Rev. B 81 041305(R)), and was mapped 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 the dot and the 2DTI based on a simple scaling dimensional analysis (Law et al 2010 Phys. Rev. B 81 041305(R). We re-examine this model beyond the bare scaling dimension analysis via a one-loop renormalization group (RG) approach combined with bosonization and re-fermionization techniques near weak-coupling and strong-coupling (2CK) fixed points. We find for a fixed value of K < 1 that the 2CK fixed point can be unstable towards the 1CK fixed point and the system is expected to undergo a quantum phase transition between 1CK and 2CK fixed points with changing Kondo couplings. Our RG approach is controlled near K = 1. In general, this QPT can also occur upon tuning the Luttinger parameter K to a critical value K-c smaller than unity (0 < K-c < 1) for fixed Konodo couplings. 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 controlled RG approach. We extract quantum critical and crossover behaviors from various thermodynamical quantities near the transition. Our results are robust against particle-hole asymmetry for 1/2 < K < 1.
URI: http://dx.doi.org/10.1088/1367-2630/17/1/013005
http://hdl.handle.net/11536/124212
ISSN: 1367-2630
DOI: 10.1088/1367-2630/17/1/013005
期刊: NEW JOURNAL OF PHYSICS
Volume: 17
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