University of Minnesota
School of Physics & Astronomy

Physics and Astronomy Calendar

Wednesday, January 20th 2016
1:25 pm:
Speaker: Cui-Zu Chang, Massachusetts Institute of Technology
Subject: From Topological Insulators to Quantum Anomalous Hall Effect

The quantum anomalous Hall (QAH) effect can be considered as the quantum Hall (QH) effect without external magnetic field, which can be realized by time reversal symmetry breaking in a topologically non-trivial system. A QAH system carries spin-polarized dissipationless chiral edge transport channels without external energy input, hence may have huge impact on future electronic and spintronic device applications with ultralow-power consumption. The many decades’ quest for the experimental realization of QAH effect received a boost in 2006 with the discovery of topological insulators (TIs). In 2013, the QAH effect was observed in thin films of Cr-doped TI for the first time [1]. In 2015, a near ideal system in V-doped TI, contrary to the expectation of first principle calculations, was demonstrated to show extremely high-precision QAH quantization with more robust magnetization and higher Curie temperature [2]. In this talk, I will introduce the route to the experimental observation of the QAH effect in above-mentioned two systems [1,2], and discuss the zero magnetic field dissipationless edge mode and the origin of the dissipative channels in the high-precision QAH state [3]. Finally I will outline the prospects and the barriers of a viable QAH-based device.
[1] Cui-Zu Chang et al, Science 340, 167(2013).
[2] Cui-Zu Chang et al, Nature Materials 14, 473(2015).
[3] Cui-Zu Chang et al, Physics Review Letters 115, 057206 (2015).

Faculty Host: Martin Greven

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