2DCC Webinars
Occurring monthly during the academic year, the 2DCC Webinars present new technical scientific news from within the 2DCC facility and the broader scientific community, as well as, broader topics such as science related to diversity. The webinars are free with an online registration. The slides with voice-over for the 2016 webinars, 2017 webinars, 2018 webinars, 2019 webinars, 2020 webinars , 2021 webinars, 2022 webinars and 2023 webinars are available by following the links in the menu.
Speaker: Dr. Zhiqiang Mao, Penn State University
Title: Layered magnetic topological materials (MnBi2Te4)(Bi2Te3)m
Abstract: The combination of magnetism and non-trivial band topology can generate potentially useful exotic quantum states of technological relevance, e.g., the quantum anomalous Hall insulator (QAHI). In this talk, I will present our recent studies on layered magnetic topological insulators (MnBi2Te4)(Bi2Te3)m (m=0, 1 & 2). This material system has recently attracted a great deal of interest, since it is predicted to provide access to a rich verity of novel topological quantum states, such as QAHI, axion insulators, high-order topological insulators and ideal Weyl semimetals [1-4]. Experimentally, there have been significant advancements in the studies of these materials. Intrinsic antiferromagnetic (AFM) topological insulators have been demonstrated in bulk single crystals of MnBi2Te4 (m=0) [3], MnBi4Te7 (m=1) [5] and MnBi6Te10 [6]. Furthermore, both QAHI [7] and axion insulators have been observed in 2D thin layers of MnBi2Te4 [8]. Our work [9-11] in this area has focused on the study of competing magnetic interactions of (MnBi2Te4)(Bi2Te3)m and the field-driven topological phase transition from the topological insulator to the ideal Weyl semimetal state in Mn(Bi1-xSbx)2Te4. While theory predicts the AFM phases are more stable than the FM phases in (MnBi2Te4)(Bi2Te3)m (m=0, 1 & 2), we have succeeded in synthesizing both AFM and FM phases for these compositions through finely tuning growth conditions and tuned their chemical potential to be close to their charge neutral points via Sb substitution for Bi. These materials provide rich opportunities for observing novel magnetic topological phases. From magnetotransport measurements on Mn(Bi1-xSbx)2Te4, we have observed clear evidence of an ideal type-II FM Weyl state in the polarized FM phase. We find the field-driven AFM-to-FM transition induces an electronic structure reconstruction in lightly hole-doped samples, which results in a large intrinsic anomalous Hall effect and negative c-axis longitudinal magnetoresistance attributable to the chiral anomaly [11]. These results establish a promising platform for exploring the underlying physics of the long-sought, ideal time-reversal-symmetry breaking type II Weyl semimetal.
On University Park campus?
Attend in person in the Millennium Science Complex N-201