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TT: Fachverband Tiefe Temperaturen

TT 35: Frustrated Magnets - Strong Spin-Orbit Coupling 1 (joint session TT/MA)

TT 35.10: Vortrag

Mittwoch, 18. März 2020, 12:15–12:30, HSZ 304

Magnetization density distribution of Sr₂IrO₄: Deviation from a local j_eff=1/2 picture — Jaehong Jeong¹, •Benjamin Lenz^2,3, Arsen Gukasov¹, Xavier Fabreges¹, Andrew Sazonov⁴, Vladimir Hutanu⁴, Alex Louat⁵, Cyril Martins⁶, Silke Biermann^3,7, Veronique Brouet⁵, Yvan Sidis¹, and Philippe Bourges¹ — ¹Laboratoire Léon Brillouin, CEA Saclay, Gif-sur-Yvette, France — ²IMPMC, Sorbonne Université, Paris, France — ³CPHT, Ecole Polytechnique, Palaiseau, France — ⁴Institute of Crystallography, RWTH Aachen, Germany — ⁵LPS, Université Paris-Saclay, Orsay, France — ⁶LCPQ, Université Paul Sabatier, Toulouse, France — ⁷Collège de France, Paris, France

5d iridium oxides are of huge interest due to the potential for new quantum states driven by strong spin-orbit coupling. The j_eff=1/2 state of Sr₂IrO₄ is such a state and consists of a quantum superposition of the three t_2g orbitals with nearly equal population, which stabilizes an unconventional Mott insulating state.
Here, we report an anisotropic and aspherical magnetization density distribution measured by polarized neutron diffraction in a magnetic field up to 5T at 4K, which strongly deviates from a local j_eff=1/2 picture. Theoretical considerations based on a momentum-dependent composition of the j_eff=1/2 orbital and an estimation of the different contributions to the magnetization density casts the applicability of an effective one-orbital j_eff=1/2 Hubbard model into doubt.
The analogy to the superconducting copper oxide systems might thus be weaker than commonly thought.