Regensburg 2016 – scientific programme

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MA: Fachverband Magnetismus

MA 14: Focus: Magnetism as seen by neutrons

MA 14.1: Invited Talk

Tuesday, March 8, 2016, 09:30–10:00, H32

Breakthrough neutron spectroscopy for quantum magnetism — •Andrey Zheludev — Laboratory for Solid State Physics, ETH Zurich, Switzerland

Quantum magnetism is an area of research where neutron scattering has always played a leading role. Neutrons directly probe the very spin correlation functions that theorists are aiming to calculate. For quantum magnets, this comparison between theory and experiment can be very detailed and quantitative. Neutrons are also a great tool for studying quantum critical phenomena in magnets, just as they were irreplaceable in the study of thermodynamic magnetic phase transitions. Recently, the topic of quantum magnetism seemed to have lost its former luster. Many systems appeared to have been “perfectly well” understood, while for the remaining unexplored models there seemed to be few material prototypes. Fortunately, these concerns are being voided by previously unimaginable breakthroughs in neutron spectroscopy instrumentation, particularly at pulsed neutron facilities. Energy resolutions of 10 µeV are now routinely used to study spin excitations in very small samples and in very difficult sample environments with unprecedented statistics and signal to noise ratios. The enormous gains in data rates now permit us to study excitation spectra in their entirety, rather than focusing on just a few sharp and intense features. Totally new physics is being uncovered in many quantum magnets that were studied and declared “understood” 15 years ago. Theorists are again barely able to keep up with neutron experiments. In my talk I shall illustrate these points with a few recent example.