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MRSEC: Layered magnetic topological semimetals and their unusual interlayer quantum transport

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Zhiqiang Mao, Tulane University
11 September 2017 from 12:00 PM to 1:00 PM
S-5 Osmond Laboratory
Contact Name
Nitin Samarth
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Recent discoveries of three dimensional topological semimetals have generated immense interests since they represent new topological states of quantum matters. In this talk, I will first introduce my group’s general research interests and then present our recent studies on topological semimetals [1-4], which are focused on Dirac/Weyl fermions generated by square lattices in layered compounds. I will report on our discoveries of new magnetic Dirac semimetals (Sr/Ba)1-yMn1-zSb2 [1,2]. In Sr1-yMn1-zSb2, Dirac fermions are found to coexist with ferromagnetism, offering a rare opportunity to investigate the interplay between relativistic fermions and spontaneous time reversal symmetry breaking and explore a possible magnetic Weyl state [1]. Then I will discuss the unusual interlayer quantum transport behavior resulting from the zeroth Landau level (LL) mode observed in type-II Weyl semimetal YbMnBi2 [3].  The interlayer magnetoresistivity and Hall conductivity of this material were found to exhibit surprising angular dependences under high fields, which can be well fitted by a model which considers the interlayer quantum tunneling transport of the zeroth LL’s Weyl fermions. Our results shed light on the unusual role of zeroth LL mode in transport. Finally I will show our experimental evidences for the topological nodal line semimetal states found in ZrSiSe and ZrSiTe [4]. Since atomically thin crystals of these two materials are accessible via mechanical exfoliation, they raise the possibility of realizing the theoretically predicted 2D topological insulators.



[1] Liu et al., Nature Materials, published online 2017, doi:10.1038/nmat4953.

[2] Liu et al., Sci. Rep. 6, 30525 (2016).

[3] Liu et al., arXiv 1608.05956, to appear in Nature Communications.

[4] Hu et al., Phys. Rev. Lett. 117, 016602 (2016) (Editor’s suggestion).