VietNam 2013 

IXth Rencontres du Vietnam
Quy-Nhon, August 4-10, 2013


 Nanophysics: from fundamentals to applications

(the return)


Monday 5
Dots and wires
Y. Gefen
› 15:30 - 16:00 (30min)
Spatial correlation in Kondo systems: Kondo cloud and quantum entanglement
Heung-Sun Sim  1@  
1 : Korea Advanced Institute of Science and Technology
Daejeon 305-701 -  South Korea

In this talk, we discuss two issues on spatial correlation in a Kondo system.

First, we propose a method to directly measure, by electrical means, the Kondo cloud formed by an Anderson impurity coupled to quantum wires, on which an electrostatic gate voltage is applied at distance L from the impurity. We show that the Kondo cloud, and hence the Kondo temperature and the electron conductance through the impurity, are affected by the gate voltage, as L decreases below the Kondo cloud length. Based on this behavior, the cloud length can be experimentally identified by changing L with a keyboard type of gate voltages or tuning the coupling strength between the impurity and the wires.

Second, we compute the entanglement of formation (EOF), an entanglement measure for mixed states which generalizes entanglement entropy used for pure states, for a Kondo impurity at finite temperature. It is well known that the computation of EOF of a many-body mixed state is a hard problem, requiring numerical optimization such as pure-state decomposition. We overcome the problem, by developing a new approach based on optimal witness operators. We predict the scaling behavior of EOF, which characterizes the temperature-dependence of the Kondo effect as well as the spatial structure of Kondo cloud.

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