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Durham University

Research & business

Research lectures, seminars and events

The events listed in this area are research seminars, workshops and lectures hosted by Durham University departments and research institutes. If you are not a member of the University, but  wish to enquire about attending one of the events please contact the organiser or host department.


 

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Events for 22 July 2020

Dr. Matjaž Gomilšek: Quantum effects in muon spin spectroscopy

1:00pm, CMP seminar via Zoom

Muon spin relaxation and rotation (muSR) is a powerful technique for probing local magnetic fields in a variety of materials via the precession of an implanted muon’s spin. Among its many advantages is exquisite sensitivity to small internal fields and a unique, broad frequency window. However, the interpretation of experimental muSR results is often complicated by an a priori unknown muon position, possible distortions of the local crystal structure, as well as quantum muon effects such as muon zero-point motion and quantum tunnelling. While there has recently been a lot of work addressing these issues in the classical, point-particle approximation via large-scale ab initio density functional theory (DFT) calculations, the effects of quantum muon motion have received substantially less attention, even though they are often expected to be substantial.
In this talk I will present our recent progress towards incorporating the effects of fully-quantum muon motion into ab initio DFT calculations via path-integral molecular dynamics (PIMD). I will demonstrate that common quantum-muon approximation schemes such as the harmonic approximation, various adiabatic schemes, and even muon–nuclear separability ansätze (i.e. the assumption of no quantum entanglement between muon and nuclear positions) all fail to describe real quantum muon motion due to the low muon mass, which can strongly amplify quantum motion effects. I will also present some recent measurements of quadrupolar level-crossing resonance (QLCR) muon spectra on solid nitrogen and our ab initio modelling of them via DFT+PIMD, and demonstrate that the shifts of the observed resonances from classical predictions can be explained by incorporating the effects of fully-quantum muon motion.https://durhamuniversity.zoom.us/j/2867509085

Contact halim.kusumaatmaja@durham.ac.uk, nikitas.gidopoulos@durham.ac.uk for more information about this event.


DEI Online Seminar Series: Helium, it's gas, gas, gas

1:00pm to 2:00pm, Online via Zoom, Prof Jon Gluyas

Contact lynn.gibson@durham.ac.uk for more information about this event.