Center for Artificial Low Dimensional Electronic Systems

Orbital order and nematicity in Fe-based superconductors

Seung-Ho Baek

July 27(Wed) - July 27(Wed), 2016

Orbital order and nematicity in Fe-based superconductors

Seung-Ho Baek

IFW Dresden

The origin of the nematic symmetry breaking in Fe-based superconductors has been heavily debated [1,2,3], because lattice, orbital, and spin degrees of freedom are all directly linked one another from a symmetry point of view, and thus it is challenging to establish which ordering is primary. In this talk, I will present nuclear magnetic resonance (NMR) studies of the high-quality FeSe [2,4,5] and LaFeAsO [6] single crystals. Although static antiferromagnetic order occurs just below the nematic transition in LaFeAsO, contrasting with FeSe in which the static magnetism is absent, our NMR studies reveal that in the two materials orbital order takes place simultaneously with the nematic transition, while triggers the enhancement of spin fluctuations. This observation suggests that orbital degree of freedom drives nematic order in Fe-based superconductors, regardless of the occurrence of static magnetic order near the nematic instability.

[1] R. Fernandes et al., Nature Physics 10, 97 (2014)

[2] S.-H. Baek et al., Nature Materials 14, 210 (2015)

[3] Q. Wang et al., Nature Materials 15, 150 (2016)

[4] J. M. Ok, S.-H. Baek et al, (unpublished, in preparation)

[5] S.-H. Baek et al., Phys. Rev. B 93, 180502(R) (2016)

[6]J. M. Ok, S.-H. Baek et al, (unpublished, in preparation)