Two-Dimensional Massless Dirac Fermions in Antiferromagnetic AFe2As2 (A=Ba,Sr)

Abstract

We report infrared studies of AFe2As2 (A=Ba, Sr), two representative parent compounds of iron-arsenide superconductors, at magnetic fields (B) up to 17.5 T. Optical transitions between Landau levels (LLs) were observed in the antiferromagnetic states of these two parent compounds. Our observation of a √B dependence of the LL transition energies, the zero-energy intercepts at B=0  T under the linear extrapolations of the transition energies and the energy ratio (∼2.4) between the observed LL transitions, combined with the linear band dispersions in two-dimensional (2D) momentum space obtained by theoretical calculations, demonstrates the existence of massless Dirac fermions in the antiferromagnet BaFe2As2. More importantly, the observed dominance of the zeroth-LL-related absorption features and the calculated bands with extremely weak dispersions along the momentum direction kz indicate that massless Dirac fermions in BaFe2As2 are 2D. Furthermore, we find that the total substitution of the barium atoms in BaFe2As2 by strontium atoms not only maintains 2D massless Dirac fermions in this system, but also enhances their Fermi velocity, which supports that the Dirac points in iron-arsenide parent compounds are topologically protected.

Description
Advisor
Degree
Type
Journal article
Keywords
Citation

Chen, Zhi-Guo, Wang, Luyang, Song, Yu, et al.. "Two-Dimensional Massless Dirac Fermions in Antiferromagnetic AFe2As2 (A=Ba,Sr)." Physical Review Letters, 119, no. 9 (2017) American Physical Society: https://doi.org/10.1103/PhysRevLett.119.096401.

Has part(s)
Forms part of
Rights
Article is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use.
Link to license
Citable link to this page