Speaker
Dr
Mark Dean
(Brookhaven National Laboratory)
Description
High resolution resonant inelastic x-ray scattering (RIXS) has recently emerged as a highly sensitive probe of magnetic excitations – it can even be used to measure magnetic excitations in isolated one-unit-cell-thick La2CuO4 layers [1]. This talk will describe how RIXS has provided new insights into the magnetic excitations in the high-temperature superconducting cuprates.
Photoemission and scanning tunneling spectroscopy have given us exquisitely detailed picture of the electronic structure of Bi2Sr2CaCu2O8+delta, but little is known about its high-energy (>100 meV) magnetic response. Using RIXS we measure the magnetic response [2] and show that a phenomenological theory based on electron pockets can consistently describe the electronic and magnetic response of this cuprate [2, 3].
In the heavily overdoped cuprates such as La2-xSrxCuO4 (x>0.3) superconductivity disappears despite the high electronic density of states. We used RIXS to measure the magnetic excitations across the whole La2-xSrxCuO4 phase diagram. The magnons induced by local moment physics in La2CuO4 evolve smoothly into broadened paramagnons in the overdoped state where itinerant quasi-particles dominate most properties of the cuprates. The fact that paramagnons persist relatively unchanged as superconductivity disappears is very difficult to reconcile with theories that suggest these high-energy paramagnons seen by RIXS, rather than the lower energy magnetic excitation in other regions of the Brillouin zone, are causing superconducting pairing [4].
[1] M. P. M. Dean et al. Nature Materials 11, 850–854 (2012)
[2] M. P. M. Dean et al. Phys. Rev. Lett. 110, 147001 (2013)
[3] A. J. A. James, T. M. Rice and R. M. Konik, Phys. Rev. B 86, 100508(R) (2012)
[4] M. P. M. Dean et al. arXiv:1303.5359 (2013) (in press at Nature Materials.)
Primary author
Dr
Mark Dean
(Brookhaven National Laboratory)
Co-authors
Dr
Andrew James
(Brookhaven National Laboratory)
Dr
Claude Monney
(Paul Scherrer Insitut)
Ms
Genda Gu
(Brookhaven National Laboratory)
Prof.
Giacomo Ghiringhelli
(Politecnico Di Milano)
Ms
Greta Dellea
(Politecnico di Milano)
Dr
Ivan Bozovic
(Brookhaven National Laboraory)
Prof.
Jeroen van den Brink
(IFW Dresden)
Dr
John Hill
(Brookhaven National Laboraory)
Dr
Kejin Zhou
(Paul Scherrer Institut)
Prof.
Lucio Braicovich
(Politecnico di Milano)
Dr
Nick Brookes
(European Syncrotron Radiation Facility)
Dr
Robert Konik
(Brookhaven National Laboratory)
Dr
Springell Ross
(University of Bristol)
Dr
Thorsten Schmitt
(Paul Scherrer Institut)
Dr
Xuerong Liu
(Brookhaven National Laboratory)
