Seminarium Fizyki Materii Skondensowanej

In contrast to collective spin excitations, the collective orbitalexcitations (orbitons) are hard to detect. However, recent advancements inresonant inelastic x-ray scattering have allowed for a rather unambiguousdetection of orbitons in the quasi-1D copper oxides [1, 2]. A closerinvestigation of the observed 1D orbiton dispersion suggested that thisdispersion could not be understood using a simple linear orbital wavepicture. Instead, it occurred that the orbiton in these materialsinteracts with the spin degrees of freedom [3, 4]. Nevertheless, due tothe quasi-1D character of these copper oxides, there is an effectivedecoupling of the orbiton from the spin excitation -- the so-calledspin-orbital separation [1-4].During the seminar I will explain in detail the idea of spin-orbitalseparation. I will show how the orbital excitation in the quasi-1Dcuprates, which actually can be understood as carrying both spin andorbital quantum numbers, can 'separate' into an independent orbiton andspinon excitation.References:[1] J. Schlappa et al.; Nature 485, 82 (2012).[2] V. Bisogni et al.; Phys. Rev. Lett in press (2015) and arxiv:1310.8346.[3] K. Wohlfeld et al.; Phys. Rev. Lett. 107, 147201 (2011).[4] K. Wohlfeld et al.; Phys. Rev. B 88, 195138 (2013).