Han's academic page

Research

I am working on several different projects in theoretical physics.

Many of these projects are centered around understanding quantum many-body systems from a high-energy theory point of view, due to my hep-th training background. More specifically, I did a lot of work looking for emergent gauge theory and gravity from many-body systems.

I have also developed a keen interest in the experimental side of physics. I like to think about what is the non-trivial physics hidden behind certain experimental signatures, as well as the experimentally realistic routes to realize some exotic states of matter.

Theme 1: Fracton matter and holography

It is well-established that gauge theories can emerge as collective phenomena in many-body systems. However, much less is known about how gravity could emerge as collective phenomena.

One very interesting aspect of fracton phases of matter is how they resemble gravity in various ways. For example, the gapless rank-2 U(1) gauge theory has effective graviton-like excitations.

What I have done is to examine the entanglement structure of fracton phases of matter and search for their connections with gravity. I realized that fracton models can be viewed as toy models of gravitational holography: when embeded in AdS space, they reproduce some of the main holographic entanglement entropy properties of gravity. Furthermore, it turns out that the rank02 U(1) gauge theory, as a linear order approximation of general relativity, has "bit-threads" as its dynamical variables, and provides a universal class for different toy models of holography.

Geodesic string condensation from symmetric tensor gauge theory: a unifying framework of holographic toy models

Han Yan
Phys. Rev. B 102, 161119 (2020)

Hyperbolic fracton model, subsystem symmetry, and holography. II. The dual eight-vertex model

Han Yan
Phys. Rev. B 100, 245138 (2019)

Hyperbolic fracton model, subsystem symmetry, and holography

Han Yan
Phys. Rev. B 99, 155126 (2019)
Featured in Editor's Suggestion and Kaleidoscope. Media coverage by OIST.

Theme 2: Emergent gauge theories in frustrated magnetism

Frustrated magnetism is a very effective mechnism to realize spin liquids. A canoncical example is the spin ice, in which frustrated Ising AFM interactions on a pyrochlore lattice spin model lead to emergent U(1) gauge structure and long-range entangled quantum states.

We have done a series of works to answer a much more generalized question: given the most general nearest-neighbour Hamiltonian, allowed by symmetry, on the pyrochlore lattice, how to determine the emergent gauge structure/Gauss' laws of the low energy states?

We have developed a field-theoretical tool-set to answer the questions above. Along the way, we have also discovered many interesting spin liquids with exotic gauge structures.

Low energy structure of spiral spin liquids

Han Yan, Johannes Reuther
Phys. Rev. Research 4 (2), 023175

Phonon induced rank-2 U (1) nematic liquid states

Han Yan, Andriy Nevidomskyy
arXiv:2108.11484

Fracton excitations in classical frustrated kagome spin models

Max Hering, Han Yan, Johannes Reuther
Phys. Rev. B 104, 064406

Rank-2 U(1) spin liquid on the breathing pyrochlore lattice

Han Yan, Owen Benton, Ludovic DC Jaubert, Nic Shannon
Phys. Rev. Lett. 124, 127203

Identification of emergent constraints and hidden order in frustrated magnets using tensorial kernel methods of machine learning

Jonas Greitemann, Ke Liu, Ludovic D. C. Jaubert, Han Yan, Nic Shannon, and Lode Pollet
Phys. Rev. B 100, 174408 (2019)
Featured on OIST news.

Competing spin liquids and hidden spin-nematic order in spin ice with frustrated transverse exchange

Owen Benton, L. D. C. Jaubert, Han Yan and Nic Shannon
Phys. Rev. X 7, 041057 (2017)

Theory of multiple-phase competition in pyrochlore magnets with anisotropic exchange with application to Yb₂Ti₂O₇, Er₂Ti₂O₇, and Er₂Sn₂O₇

Han Yan, Owen Benton, L.D.C. Jaubert and Nic Shannon
Phys. Rev. B 95, 094422 (2017)
Identified by Web of Science as being in the top 1% of Physics publications on the basis of citations in the field and publication year; top 10 most-cited papers in Phys. Rev. B in 2017.

From pinch points to pinch lines: a new spin liquid on the pyrochlore lattice

Owen Benton, L. D. C. Jaubert, Han Yan and Nic Shannon
Nature Communications 7, 11572 (2016)
Featured on OIST news.

Theme 3: Experimental connections

These projects are to study materials we found interesting, and understand the meaning of certain experimental signatures.

Sleuthing out exotic quantum spin liquidity in the pyrochlore magnet Ce₂Zr₂O₇

Anish Bhardwaj, Shu Zhang, Han Yan, Roderich Moessner, Andriy H Nevidomskyy, Hitesh J Changlani

npj Quantum Materials 7, 51 (2022)
Featured on Rice News.

Theory of Ca₁₀Cr₇O₂₈ as a bilayer breathing-kagome magnet: Classical thermodynamics and semi-classical dynamics

Rico Pohle, Han Yan, Nic Shannon
Phys. Rev. B 104, 024426

An earlier version of thie paper is on arXiv as a preprint: arXiv:1711.03778

Half moons are pinch points with dispersion

Han Yan, Rico Pohle, Nic Shannon
Phys. Rev. B 98, 140402(R). Featured in Editor's Suggestion and Kaleidoscope.
Featured on OIST news.

Experimental signatures of emergent quantum electrodynamics in Pr₂Hf₂O₇

Romain Sibille, Nicolas Gauthier, Han Yan, Monica Ciomaga Hatnean, Jacques Ollivier, Barry Winn, Geetha Balakrishnan, Michel Kenzelmann, Nic Shannon, Tom Fennell
Nature Physics 14, 711-715 (2018)
Featured on OIST news.

Other research

These high-energy phenomenology publications were my research during undergrad.

W_H/Z_H production associated with a T-odd (anti)quark at the LHC in next-to-leading order QCD

Zhang Ren-You, Yan Han, Ma Wen-Gan, Wang Shao-Ming, Guo Lei, and Han Liang
Phys. Rev. D 85, 015017

QCD next-to-leading order predictions to W-pair production in association with a massive (anti)bottom jet at the LHC

Han Yan, Shao-Ming Wang, Wen-Gan Ma, Ren-You Zhang, and Lei Guo
Phys. Rev. D 84, 014009

Google Sites

Report abuse