Physics – Condensed Matter – Mesoscale and Nanoscale Physics
Scientific paper
2009-04-15
Phys. Rev. B 81, 041305 (2010)
Physics
Condensed Matter
Mesoscale and Nanoscale Physics
4+\epsilon pages
Scientific paper
In this work, a quantum dot couples to two helical edge states of a 2D topological insulator through weak tunnelings is studied. We show that if the electron interactions on the edge states are repulsive, with Luttinger liquid parameter $ K < 1 $, the system flows to a stable two-channel fixed point at low temperatures. This is in contrast to the case of a quantum dot couples to two Luttinger liquid leads. In the latter case, a strong electron-electron repulsion is needed, with $ K<1/2 $, to reach the two-channel fixed point. This two-channel fixed point is described by a boundary Sine-Gordon Hamiltonian with a $K$ dependent boundary term. The impurity entropy at zero temperature is shown to be $ \ln\sqrt{2K} $. The impurity specific heat is $C \propto T^{\frac{2}{K}-2}$ when $ 2/3 < K < 1 $, and $ C \propto T$ when $ K<2/3$. We also show that the linear conductance across the two helical edges has non-trivial temperature dependence as a result of the renormalization group flow.
Law K. T.
Lee Patrick A.
Ng Tai Kai
Seng Chien Yeah
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