I just presented a talk“Quenching to field-stabilized magnetization plateaus in the unfrustrated Ising antiferromagnet” based on my preprint that I posted on arXiv last week at the Annual Meeting of the Physical Society of Taiwan at National Pingtung University in Pingtung, Taiwan. I haven’t gotten around to making a post about this paper yet (that is coming soon), but in the meantime I will post my slides from this talk here. My slides included some movies of the process of freezing in to magnetization plateaus. Since PDFs can’t include movies I will post the movies below.

Rubem Mondaini was kind enough to invite to visit his group and give a seminar at the Computational Science Research Center–Beijing. My talk, “Accessing Quantum Criticality with Magnetic Field Effects: Metamagnetism and Deconfinement” covered all of my work on the J-Q model, the saturation transitions in 1D and 2D (metamagnetism and zero-scale-factor universality) up to the latest updates on my work with Harley Scammell and Oleg Sushkov studying thermodynamics of field-induced spinons at the deconfined quantum critical point in the 2D J-Q model. I got some great feedback that will help me put the finishing touches on my manuscript.

After the seminar I had chance to meet with Rubem’s students and postdocs, Chen Cheng, Sabyasachi Tarat and Can Shao and learn about the fascinating things they are working on. After that, a delicious dinner!

I didn’t remember to get a picture of me at my talk, but I did get a photo of all of us out to dinner. I hope to be back to CSRC soon!

Title: Accessing Quantum Criticality with Magnetic Field Effects: Metamagnetism and Deconfinement

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 Néel 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).

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).