Earlier this year David Campbell nominated my dissertation for a Springer Thesis Award. I’m proud to say that my dissertation won and it is now available from Springer. My dissertation covers almost all of the research I did during my PhD, focusing on magnetic field effects on quantum antiferromagnets, specifically metamagnetism and deconfined quantum criticality. I’m especially proud of my introduction (Ch. 1), which I tried to make accessible to a relatively broad audience, and my methods chapter (Ch. 5), a detailed pedagogical guide to the numerical methods I used in my work.
In Chapter 1 I describe the historical and scientific context for both the study I have undertaken and the methods I have used to do it. In doing so, I tell the story of Dr. Arianna Wright Rosenbluth, the woman physicist who wrote the first-ever modern Monte Carlo algorithm in 1953. To my knowledge this is the most complete account of her life ever published.
Chapter 2 is a lightly edited version of my 2017 Phys. Rev. B paper on metamagnetism and zero-scale-factor universality in the 1D J-Q model. In Chapter 3 I discuss these same features in the 2D J-Q model. Most of Chapter 3 has been published in my 2018 Phys. Rev. B paper, but the Springer version includes an additional analysis where we look at an alternative form of the logarithmic corrections to the zero-scale-factor universality based on the 4D Ising universality.
In Chapter 4 I study the deconfined quantum critical point separating the Néel and VBS phases in the 2D J-Q model. Using a field, I force a nonzero density of magnetic excitations and show that their thermodynamic behavior is consistent with deconfined spinons (the fractional excitations predicted by deconfined quantum criticality). I also discuss a field-induced BKT transition and non-monotonic temperature dependence of magnetization, a little-known feature of this type of transition.
Finally, in Chapter 5 I provide a detailed pedagogical description of my methods focusing on stochastic series expansion quantum Monte Carlo and extensions thereof. Little in this chapter is my invention, but many of the details of these techniques have not been described in detail anywhere else in the literature (another resource is Sandvik’s excellent review article).
If you’re interested in using my dissertation, please let me know and I can send you a PDF!
Tomorrow I’m getting on a plane to Bengaluru, India for the 2nd Asia Pacific Workshop on Quantum Magnetism at ICTS Bangalore. I’m looking forward to nine straight days of tutorials and research talks. I’ll also present my poster on my work with Harley Scammell and Oleg Sushkov on direct detection of deconfined spinons, the feedback should be very helpful in finalizing our manuscript on this topic. India (Mumbai) was the location of my first major research trip, I’m eager to complete that loop and see Bengaluru!
Last Friday, the 26th General Conference on Weights and Measures voted to replace “Le Grand K”, the 129 year old physical prototype of the kilogram, with a new measure based on physical constants. The new definition, which comes in to force next spring, is now fixed by defining the Plank constant as exactly 6.626 070 15 x 10-34 Joule seconds.
The kilogram was the last SI unit based on a physical prototype (which means that until next year, Le Grand K is, by definition, exactly one kilogram). Other prototypes, such as the physical meter, have been long since retired. This redefinition is a triumph of high-precision experimental physics. The problem with physical prototypes for units is that they can change. Le Grand K, for example, has been losing mass, to the tune of about 50 micrograms (5 parts in 100 million), possibly because the identical cylinders it is compared to have gotten dirty from being handled more often.
Farewell Le Grand K! Thank you for your service!
This month’s Physics Today has a great article by Roberto Zenit and Javier Rodríguez-Rodríguez about the physics that governs bubbly drinks. It is relatively nontechnical (aside from a few equations which can be safely ignored).
The fluid mechanics of bubbly drinks
Roberto Zenit and Javier Rodríguez-Rodríguez
Physics Today 71 11 44 (2018)
If you have three minutes every month to devote to keeping up with science policy, I highly recommend subscribing to APS’s Signal Boost. Signal Boost is a monthly video update about key developments in science policy. Among other things, they provide critical information on the budgeting process for science funding in the House and Senate along with how to contact your elected officials about each issue. Scientists are a small group, so we need to speak up to be heard.
This month: appropriations and a bill to fight harassment in STEM:
Last week I was invited to give a seminar “Quantum criticality under the influence of magnetic fields” as a part of the Center for Quantum Science and Engineering (CQSE) series at NTU. Thanks to Prof. Guin-Dar Lin for the invitation and for Zih-Ying Huang for taking this photo of me presenting.
My research group at NTU (headed by Prof. Ying-Jer Kao) has a new website. Take a look here: