Orbital-selective Mott physics in iron-based ladder systems*

Superconductivity in Fe-based two-leg ladder materials under high pressure was discovered [1] opening new directions to improve our understanding of iron-based superconductors. Numerical studies of strongly correlated electronic multi-orbital models can be performed with high accuracy in quasi-one dimension using numerical techniques, such as DMRG. We found exotic states in these systems arising from the Hubbard and Hund interactions.

 

An ``Orbital Selective Mott Phase'' (OSMP) characterized by the formation of magnetic block states in which a block of N spins up alternate with a block of N spins down [2,3,4,5] was observed in a wide range of Hubbard and Hund couplings and electronic fillings. Neutron-scattering experiments on iron-based 123 ladder materials, where OSMP is relevant, already confirmed our theoretical prediction of block magnetism (magnetic order of the form ↑↑↓↓) [6].

 

In addition, we found that competing energy scales present in the low-dimensional OSMP induce a new kind of exotic magnetic order, the block–spiral state [4] with magnetic islands forming a spiral propagating through the chain but with the blocks rigidly rotating. The block–spiral state is stabilized without any apparent frustration, the common avenue to generate spiral arrangements in multiferroics. By examining the behavior of the electronic degrees of freedom, parity-breaking quasiparticles were revealed [4]. We also numerically predicted that OSMP could be observed in Ce2O2FeSe2 [7].

References:

 

[1] H. Takahashi et al., Nat. Mater. 14, 1008 (2015); J. Ying et al., PRB 95, 241109(R) (2017).

[2] J. Herbrych et al., Nat. Comm. 9, 3736 (2018)

[3] J. Herbrych et al., PRL 123, 027203 (2019)

[4] J. Herbrych et al., PNAS 117, 16226 (2020)

[5] J. Herbrych et al., Phys. Rev. B 102, 115134 (2020).

[6] M. Mourigal et al., Phys. Rev. Lett. 115, 047401 (2015).

[7] Ling-Fang Lin et al., Phys. Rev. B 105, 075119 (2022).