Today and tomorrow I’m visiting National Cheng Kung University (成功大學) in Tainan. I was graciously invited to give a seminar by Prof. Ching-Hao Chang (thanks!). If anyone reading this wants to chat, I’ll be visiting until Tuesday afternoon. I’m staying in the fourth-floor visitor’s office.
Title: Accessing quantum criticality with magnetic field effects: metamagnetism and deconfined quantum criticality Abstract: Simple models of interacting quantum spins (like the Heisenberg model) are remarkable tools for understanding strong quantum fluctuations, but relatively few studies have considered the effects of external magnetic fields on these systems. I investigate the influence of magnetic fields in the J-Q model, an antiferromagnetic Heisenberg model with an added 4-spin interaction (Q). This model is known to harbor a direct, continuous phase transition between the Nel state and a valence-bond solid. This transition is believed to be an example of deconfined quantum criticality, where the excitations are exotic fractionalized particles known as spinons (S=1/2 bosons). We study the thermodynamics of the excitations and find direct evidence that they are indeed fractional. Separately, we also find that the four-spin term changes the nature of the saturation transition from “zero-scale-factor” universality to metamagnetism (magnetization jumps).
I was walking by the SpringerNature booth at the March Meeting and the agent I worked with (Sam Harrison) pointed out that a print copy of my dissertation was there, on display and for sale! Truly a surreal experience!
Me and my dissertation on display at the March Meeting. Thanks to Sam Harrison for taking this picture for me.
I’m about to set off to Boston for the APS March Meeting 2019 (March 4-8). I’ll be presenting my newest work on using infinite boundary conditions are current reservoirs for measuring steady-state currents in quantum wires using tensor network methods. My talk is at Wednesday 6 March at 8:48am in room 156C. If you want to chat with me at the March Meeting drop me a line.
After the March Meeting I’ll be visiting the Sandvik group at Boston University 11-20 March. I’m really looking forward to seeing all my old friends and colleagues at BU.
Established just three years ago, FECS is is dedicated to helping APS meet the unique needs of early career scientists (i.e. postdocs). Early career scientists face a number of unique challenges. They often move great distances, isolating themselves from their support networks. They have neither the protection of tenure nor the comradeship of classmates, and they often occupy temporary positions with low pay, meager benefits, and few labor protections. They must balance the pressure to publish with the constant search for their next position. All of these factors put them at an elevated risk for exploitation and harassment, the worst of which often falls upon women and minorities.
I am looking forward to working to make life better for early career scientists like myself. I want to focus especially on the problems faced by underrepresented minorities as well as mental health. In addition to my own ideas, I want to hear from you, my friends and colleagues, about issues that are facing early career scientists and ideas for how FECS might be able to address them. Please contact me or comment below with your thoughts and suggestions.
If you’re an APS member who is interested in joining FECS, you can do so for free by logging into your account on aps.org. You can also join the FECS Facebook group, even if you’re not an APS member.
This conference was very local: only about 10% of the participants were from abroad (I’m uncertain if that figure includes people like me). They were nonetheless able to get some pretty good invited speakers including my PhD supervisor, Anders Sandvik, and Nobel Laureate and former US Secretary of Energy Steven Chu. I was honored to shake Secretary Chu’s hand at the banquet (unfortunately, there is no selfie).
I gave a talk based on thermodynamics of deconfined spinons in a magnetic field, the same topic as my poster from the ICAM-NCTS.
I had great conversations with Taiwanese physicists, including some new potential collaborators. I was also able to catch up with my PhD supervisor, Anders Sandvik to discuss some aspects of the modifications I am making to my QMC code in order to measure off-diagonal imaginary-time correlations.
As a bonus, while walking from my hotel to the conference I stumbled upon the NTHU Research Reactor. I’ve always wanted to see the inside of a nuclear reactor, but I never managed to get a tour of the MIT research reactor (despite living only blocks away from it in Cambridge, MA). Hopefully I can get a tour of this one.
Last week I attended the NCTS-ICAM Annual Meeting and Workshop at National Tsing-Hua University (清華大學) in Hsinchu (新竹), Taiwan. It was a delightful week of presentations and discussions with condensed matter physicists from all over the world and an excellent opportunity to build my professional network here in Taiwan.
I presented my poster “Direct numerical observation of Bose-Einstein condensation of deconfined spinons” in which I use a magnetic field to induce a finite density of magnetic excitations at a deconfined quantum critical point and use thermodynamics to show that they must be deconfined spinons (an extension of Ch. 4 of my dissertation). I received some excellent feedback on my poster that will help improve my manuscript.
There were fascinating talks including David Campbell, Duncan Haldane, Nic Shannon and Suchitra Sebastian. ICAM also made the wise decision to include a panel discussion on women in physics as part of the main schedule (rather than in a parallel session or as an extra event). It was a great opportunity to hear from women physicists about the challenges they face and to get some updated data from Laura Greene (former president of APS).
Part of the conference was an excursion to 南圓 (Nanyuan), a beautiful resort in the foggy mountains near Hsinchu. We had a tour of the beautiful Chinese garden and partook in a tea ceremony.