University of Minnesota
School of Physics & Astronomy

Condensed Matter Seminar

Wednesday, September 12th 2018
1:25 pm:
Speaker: Elbio Dagotto, University of Tennessee, Knoxville and Oak Ridge National Laboratory
Subject: Iron-Based High-Tc Superconductors: Brief Review and New Results in Superconducting Ladders BaFe2S3 and BaFe2Se3

The field of iron-based high critical temperature superconductors continues attracting the attention of the Condensed Matter Physics community. I will briefly review the main ideas in this field and argue that electronic correlation effects cannot be neglected [1]. For this reason, in the main portion of the presentation I will focus on recent exciting results for the two-leg ladder compounds BaFe2S3 and BaFe2Se3.These are the only members of the iron-based family that were reported to become superconducting (at high pressure) without having iron layers in its crystal structure [2]. Theory becomes more accurate in 1D and numerically exact computational results for a two-orbital Hubbard model applied to ladders, as well as chains, will be discussed [3]. They reproduce the dominant magnetic order of BaFe2S3 and BaFe2Se3, and display intriguing indications of pairing tendencies upon doping at intermediate Hubbard couplings. I will speculate that this may be explained by the existence of unexpected preformed spin-singlets in the system [4]. Recent results for the dynamical spin structure factor of ladders S(q,) will also be briefly discussed, time allowing, and compared with neutron scattering data [5]. Novel optical modes are predicted.

[1] P. Dai et al., Nat. Phys. 8, 709 (2012), and references therein.
[2] H. Takahashi et al., Nat. Mater. 14, 1008 (2015); T. Yamauchi et al., PRL 115, 246402 (2015); J.-J. Ying et al., PRB 95, 241109 (R) (2017).
[3] N. D. Patel et al., PRB 94, 075119 (2016); PRB 96, 024520 (2017).
[4] N. D. Patel et al., in preparation.
[4] J. Herbrych et al., accepted in Nat. Communications 2018.

Faculty Host: Rafael Fernandes

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