Origins of the hourglass dispersion in layered cobaltates

  • Peter Babkevich Laboratory for Quantum Magnetism, École Polytechnique Fédérale de Lausanne


The interplay between uni-directional charge and spin stripe correlations in copper oxide-based high-temperature superconductors is a matter of long-standing debate . While static magnetic stripe order has been shown to compete with superconductivity, fluctuating stripes have been argued to play an important role in the pairing mechanism of unconventional superconductors. By probing the magnetic correlations of hole-doped layered copper oxide superconductors using inelastic neutron scattering, a universal spectrum has been resolved whose shape in momentum-energy resembles an hourglass. Its origin or even if the system should be considered in the local-moment or itinerant framework has been the subject of debate for some time.

I shall present our research into the insulating, layered cobalt oxide La2-xSrxCoO4—an isostructural analogue of the copper oxide superconductors. Our measurements have revealed that it also has a characteristic hourglass dispersion that we could explain using a parameter-free model based on a stripe-ordered magnetic ground state. However, direct evidence for stripe-order was missing and led to some studies to propose a stripe-free scenario to explain the dispersion. I shall present our polarised neutron diffraction results to examine the magnetic order in La2-xSrxCoO4 and discuss its implications on the role of stripes forming an hourglass spectrum.

About the Speaker

Peter Babkevich received his PhD degree in Condensed Matter Physics from the University of Oxford. During this time, he was a visiting student at the Paul Scherrer Institute in Switzerland. Since 2012, he has been working as a postdoctoral researcher in the Laboratory for Quantum Magnetism at the Swiss Federal Institute of Technology (EPFL) in Lausanne. His expertise includes using a wide range of neutron scattering and magnetic resonance methods to study magnetic phenomena in Mott insulators, unconventional superconductivity in iron-based systems, spin-1/2 square-lattice Heisenberg antiferromagnets, multiferroics, and rare-earth magnetism. Not content with just performing the experiments, his experience extends to applying varied theoretical approaches to analyze and interpret these measurements further.

How to Cite
P. Babkevich. Origins of the hourglass dispersion in layered cobaltates, Proceedings of the Samahang Pisika ng Pilipinas 36, SPP-2018-INV-3C-06 (2018). URL: