Log · Research

Conference Log: CMP In The City 2017

Another week, another conference log! This is probably my last one for the foreseeable future – I’m a bit conferenced out at this point…

Last week I was at Condensed Matter Physics in the City (CMP) in London. I received an ICAM funding award to attend, so before I go much further I should tip my hat to ICAM and the powers that be that chose to fund me – much obliged! It was fantastic to be back in London again – I always enjoy my time there. (In fact, I’d love to live there one day – hint hint, anyone who might want to offer me a job in the very near future…)

CMP is a bit different to most conferences in that it’s very informal and interactive, with significant discussion time built into the schedule. For example, my talk was 30 minutes plus 15 minutes discussion. In practice, the discussion usually takes place during the talk – this is not a conference to attend if you want to deliver a word-perfect talk without interruptions!

I was there to talk about my recent work on many-body localisation and the technique we’ve developed to look at the dynamics of many-body localised phases. It was essentially a smoother, better-rehearsed version of my talk that I gave at King’s College last month, except the punchline was different. Having spent another month gathering more data, improving my analysis and shoring up my conclusions, the tentative conclusion I advanced at WOLQS no longer looks valid: things are getting interesting!

Screen Shot 2017-07-17 at 00.46.05
I’m lacking pictures for this post, so here’s a screenshot of one of my slides to make up for it. You’re welcome.

I think my talk went pretty well, if I say so myself – the last time I spoke at this conference in 2014, unprepared for its interactive nature, I was flayed alive by one of the audience members. This time around, with 3 more years of experience under my belt, batting back the questions was a lot easier. I received some very interesting and useful feedback in response to my talk that we’ll take into account when we finalise the paper we’re currently writing – my thanks to all the audience members for their questions and discussions over the course of the week.

There isn’t the space here to give even short summaries of every talk as I’ve done previously, so I’m just going to go through a handful of the ones I found most interesting (with links to research papers where I could find them). This isn’t remotely comprehensive and is extremely biased towards my own interests – my apologies to the other speakers!

(The full speaker list may be found here, for those interested. Despite all the good things about CMP that I have and will continue to mention in this post, there’s a really important negative point that needs acknowledging up front: look at all the names in that list and see if you can spot what almost all have in common. Gender equality is slowly improving in physics, but we still have a long way to go – this conference in particular was disproportionately lacking in female speakers compared to others I’ve been to recently. From conversations I had with some of the organisers, they’re clearly aware of the need to address such inequality in physics – I do hope that next year’s CMP will be more representative of the entire research community.)

We had two very interesting talks from Timon Hilker of LMU Munich about quantum gas microscopes and ultracold atomic gases – I have a documented fondness for these experimental setups, so I enjoyed these talks, as well as a chat I had with Timon over lunch one day where I advanced some new ideas I had for experiments and he patiently explained to me just how difficult they’d be. (But not impossible, mind…)

quantum-gas-microscope-sketch
An illustration of a quantum gas microscope setup – the atoms (red dots) are in a 2D plane with the lens above them.

Hubert Saleur of IPhT, who I’d somehow never met before despite working in the same building for 9 months, spoke about quantum entanglement from less of a condensed matter point of view and more from the viewpoint of field theory. I was intrigued by some of the methods he was using to calculate entanglement entropy – I may look into this a little more in the future.

Aditi Mitra from NYU gave two fantastic talks about out-of-equilibrium quantum physics. The first was on the behaviour of quantum systems after quenches, which I’d seen parts of before. The second was on how the application of periodic drive to a quantum system (i.e. shaking it) could stabilise superconducting behaviour that wasn’t stable in the regular un-shaken system, which is incredibly interesting – could driving a system be a practical way to engineer its quantum behaviour?

Gunnar Möller from the University of Kent gave a cool talk about ‘genons’, which are topological defects in materials – essentially a change to the crystal structure that disconnects atoms from their neighbours and reconnects them to others, which leads to unusual electronic properties. These could perhaps be generated in cold atoms experiments with holographic trapping potentials – my favourite experimental setup again!

480px-penrose_tiling_28rhombi29-svg
An example of a quasi-crystalline structure, in this case a Penrose tiling. Despite being clearly ordered, there is no long-range periodicity. [Image: Wikimedia Commons]
Anuradha Jagannathan from Universite Paris-Sud (very nearby to IPhT) gave two really interesting talks about quasicrystals – these are materials which are ordered in the sense that they appear to be constructed in a very deliberate way with a strict set of rules, however if you zoom out and look at the crystal as a whole you find that it doesn’t have a regular repeating structure. It breaks ‘translational invariance’, in physics-speak. I know very little about quasicrystals, but they’re a fascinating type of structure perched right on the edge between order and randomness. I really enjoyed Anu’s talks and I learned a lot from them.

Frank Pollmann of TU Munich gave two talks, one on many-body localised systems and one on quantum spin liquids. I enjoyed these talks, particularly the MBL one since that’s my own research area. The concept of quantum mutual information was a new one to me, but it looks like a really neat way to get information about MBL systems. This talk included a longer, more in-depth introduction to MBL than I had time to give in mine – it’s unfortunate that my talk came earlier in the schedule, but given that the audience for CMP fluctuates wildly from day-to-day, there was no harm in a little repetition!

Seamus Davis from Cornell told us about his group’s recent STM work on a newly-discovered orbital pairing mechanism that might drive superconductivity in a material called FeSe, and what it might mean for unlocking the secrets of superconductivity. In the past, I’ve often found it hard to understand their (admittedly colourful!) datasets, but this time around I certainly followed the main points of the argument – interesting stuff.

For the first time since I graduated, I got to see what my PhD advisor is up to these days – Frank Krüger of UCL/LCN spoke about the theory work he’s been doing on a recent experiment run by his theorist (!) colleague Paul McClarty at the ISIS Neutron & Muon Source. Using neutron scattering, they mapped out the band structure of a certain type of magnet with a crystal structure known as a Shastry-Sutherland magnet – surprisingly, they found evidence for so-called topological triplon modes, meaning that the material behaves in an unexpectedly exotic way. The existence of topological features in the excitations of a dimerised quantum magnet is a really interesting concept!

My apologies to the other speakers whose work I have not featured here – Adam Nahum, Zohar Ringel, Gonzalo Camacho, Tibor Rakovsky, Fernando Iemini, Amalia Coldea, Luke Rhodes, Vijay Narayan, Gareth Conduit, Gary Goldstein and Bogdan Galilo – and my thanks to the organisers Mathias Eschrig, Giovanni Sordi, Piers Coleman, Sam Carr, Gunnar Möller, Andrew Green, Frank Krüger and any others who I didn’t get a chance to meet during the week.

Many of the participants from CMP are off to SCES in Prague this week, but not me. I’m off home to Scotland for a few weeks holiday – or at least more relaxed working conditions than usual, while we try to get this latest paper finished and submitted! For more on that soon, watch this space…

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