| 报告题目 | Toward robust quantum anomalous Hall effect |
| 报告人 | Associate Professor Weida Wu |
| 报告人单位 | Department of Physics and Astronomy, Rutgers University |
| 报告时间 | 2018-08-17 |
| 报告地点 | 合肥微尺度物质科学国家研究中心九楼会议室（9004） |
| 主办单位 | 合肥微尺度物质科学国家研究中心 |
| 报告介绍 | Abstract：
Quantum anomalous Hall (QAH) systems are of great fundamental interest and of potential application (e.g. quantum computing) because of dissipationless conduction without external magnetic field.1–3 The QAH effect has been realized in magnetically doped topological insulator (TI) thin films.4–7 However, full quantization requires extremely low temperature (<50 mK) in the initial works, though it was significantly improved with either modulation doping or co-doping of magnetic elements.8,9 Improved ferromagnetism was indicated in the Cr and V coped TI thin films, yet a direct evidence of long-range ferromagnetic order is lacking. In this talk, I will present direct evidence of long-range ferromagnetic order in thin films of Cr and V co-doped (Bi,Sb)2Te3 using low-temperature magnetic force microscopy (MFM) with in-situ transport. The magnetization reversal process reveals a typical ferromagnetic domain behavior, i.e., domain nucleation and domain wall propagation, in contrast to much weaker magnetic signals observed in the end members, possibly due to superparamagnetic behavior observed in Cr doped TI films.10,11 If time allows, preliminary results of spectroscopy imaging of Cr and V defects in Sb2Te3 will also be presented. The observed long-range ferromagnetic order resolves one of the major challenges in QAH systems, and paves the way to high-temperature dissipationless conduction and exotic phenomena such as Axion magnetoelectric effect12.
References:
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3.Yu, R. et al. Science 329, 61–64 (2010).
4.Chang, C.-Z. et al. Science 340, 167–170 (2013).
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6.Kou, X. et al. Nat Commun 6, 8474 (2015).
7.Chang, C. Z. et al. Nat Mater 14, 473–477 (2015).
8.Ou, Y. et al. Adv Mater 30, 1703062 (2017).
9.Mogi, M. et al. Appl. Phys. Lett. 107, 182401 (2015).
10.Lachman, E. O. et al. Sci. Adv. 1, 1500740 (2015).
11.Lachman, E. O. et al. npj Quantum Mater. 2, 70 (2017).
12.Xiao, D. et al. Phys. Rev. Lett. 120, 56801 (2018). |
