主题：重庆大学现代物理中心系列学术报告

现代物理中心系列学术报告 Title: Kondo spin correations and entanglements Speaker: Sam Young Cho (Chongqing University 曹三永) Places: Science Building NO.309 Thursday (May 10th) PM 3:00 In order to quantify quantum entanglement in two-impurity Kondo system, we calculate the concurrence negativity,and von Neumann entropy. The entanglement of the two Kondo impurities is shown to be determined by two competing many-body effects, namely the Kondo effect and the Ruderman-Kittel-Kasuya-Yosida (RKKY)interaction,I. Due to the spin-rotational invariance of the ground state, the concurrence and the negativity are uniquely determined by the spin-spin correlation between the impurities. It is found that there exists a critical minimum value of the antiferromagnetic correlation between the impurity spins which is necessary for entanglement of the two impurity spins. The critical value is discussed in relation with the unstable fixed point in the two-impurity Kondo problem. Specifically, at the fixed point there is no entanglement between the impurity spins. Entanglement will only be created if the RKKY interaction exchange energy, I, is at least several times larger than the Kondo temperature, Tk. Quantitative criteria for QIP are given in terms of the impurity spin-spin correlation.