I’ve just spent a really fun few days at King’s College London, at the PhD-student-run Workshop on Localisation in Quantum Systems, and since I blogged last week about the general research area I work in, I thought I’d do a little write-up of the workshop for anyone interested who couldn’t attend. Apologies that this is a little more technical than some of my posts; it’s kind of unavoidable when discussing cutting-edge, work-in-progress research.
There were three invited speakers, Prof Vladimir Kravtsov of ICTP Trieste, Dr Zlatko Papić of the University of Leeds and Dr Vladimir Dobrosavljević of Florida State University, and each gave two talks – a general introduction to their topic, followed by a more in-depth presentation of their own research.
Kravtsov talked about multifractality in quantum systems, focusing on peculiar geometric structures such as Bethe lattices and Random Regular Graphs. The idea here is that the statistics of particles moving in these sorts of crystal lattices might be related to the statistics of real electrons in real materials, and that understanding these exotic geometries might tell us something about the wavefunctions of the real electrons, and in particular might shed some light on the transition between the localised (insulating) state and the regular metallic state of strongly disordered metals.
Papić then told us all about many-body localisation and focused on the strange quantum entanglement properties and what they can tell us – his talks were my favourite of the workshop, though that’s possibly at least in part because his work overlapped quite strongly with mine. He showed us how we can use the quantum entanglement properties of materials to gain some insight into the underlying physics, and even did a live demonstration of some of the types of calculations we could perform using relatively simple computer simulations.
Dobrosavljević spoke about the transitions between metallic and insulating states, and how his research using Dynamical Mean-Field Theory (DMFT) can shed some light on this problem. His talks linked surprisingly well to some of my previous PhD research, though the techniques he was using were new to me. Less abstract than Kravtsov’s talk and covering a more mature research field than Papić’s, Dobrosavljević’s talk took in decades of research using DMFT techniques.
Then, there were five contributed talks, selected from the attendees by the organisers. First up was Dr Francesca Pietracaprina of Sapienza Università di Roma, who spoke about her new research into what quantum entanglement can tell us about many-body localisation, and also presented a poster with some of her earlier studies of how energy dissipates in disordered materials. Taken together, these studies shed some light on the possible ‘bad metal’ phase lurking between the regular metal and curious MBL phase – a mystery wrapped in an enigma if ever there was one.
Next up was me, speaking for the first time about my own new work where I’ve been developing a technique to study the dynamics of strongly interacting, strongly disordered materials out of equilibrium, capable of investigating system sizes much larger than all competing methods I’m aware of. I outlined the technique and showed some as-yet unpublished data that’s consistent with the suggested behaviour of these systems, but I’m still gathering enough data to be able to confirm or refute some controversial points. I got a lot of questions afterwards and people seemed quite interested, so I think (hope?) my work was well received. (With thanks to my IPhT colleague Dr Valentina Ros for her invaluable expert advice during the preparation of my talk.)
Then came Adam Smith, PhD student at the University of Cambridge, talking about whether it was possible to cause localisation without disorder, something that common wisdom would say is impossible. Using a really neat model, his work suggests this might indeed be possible after all. We had one experimental physicist speaking next, Dr Erik Piatti of the Politecnico di Torino and the Cambridge Graphene Centre, presenting some of his experimental data on graphene and showing how his detailed experiments allows him to investigate some very subtle properties of the materials. The final contributed talk was Dr Paolo Barucca who focused on the statistical properties of random matrices and localisation as applied to financial market analysis – the more immediate real-world nature of this was a nice change of pace from the more abstract work most of the real of us talked about.
There was also a poster session where a number of other people presented their work. Most relevant to my interests were the posters by organiser Davide Facoetti and Dr Pietracaprina. Davide presented a really neat bit of work involving the statistics of random matrices and did an excellent job of explaining to me some of the details from Kravtsov’s talk that went far over my head. (In my defence, I’m very much a cond-mat kinda guy – statistical physics is not my comfort zone!)
I also got to briefly chat with the external examiner for my PhD thesis, Dr Joe Bhaseen. It was great to speak with him again in a less stressful situation than my PhD defence! I’m pretty sure it’s too late for him to change his mind and take my PhD away, but all the same I was relieved at his positive response to my post-PhD research.
All in all, it was a fantastic workshop, extremely well organised by a group of students with no prior experience at arranging a conference. Excellent work all round, organisers – and bonus points for taking us to a great little Italian restaurant too!