Research direction 01

Phonons

Topology · dynamics · spectroscopy

I build a concept-to-experiment program for topological lattice excitations, connecting crystal symmetry and first-principles dynamics with automated discovery and momentum-resolved spectroscopy.

Symmetry design
HT-TPHONON
High throughput
EELS

Featured work

Topology made visible.

Each project connects a distinct scientific question with the calculation, platform, or measurement that made it answerable.

Experimental and calculated phonon dispersions and gap maps showing nodal rings in graphene — Experiment and calculation resolve two nodal rings in graphene. Figure 3 from Li et al., Physical Review Letters 131, 116602 (2023), © American Physical Society.

01 Physical Review Letters · 2023

Direct observation of topological phonons in graphene.

Full-zone high-resolution electron energy-loss spectroscopy mapped phonons throughout the two-dimensional Brillouin zone, revealing two nodal rings and the band-crossing signatures of all four predicted Dirac-phonon classes.

The experiment directly confirmed the LA–ZO nodal ring and Dirac phonons predicted in the 2020 PRB study below; it also resolved a second TA–ZO nodal ring.

Graphene
EELS
Nodal rings

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Taxonomy connecting Weyl phonons, a nodal ring, a Hopf link, and a nodal net — Symmetry connects Weyl points with nodal rings, Hopf links, and nodal nets. Figure 6 from Li et al., Nature Communications 12, 1204 (2021), CC BY 4.0.

02 Nature Communications · 2021

A materials-scale atlas of topological phonons.

An automated workflow converted first-principles force constants into band-crossing searches, topological diagnostics, and boundary spectra. Screening more than 10,000 materials produced a catalog of 5,014 topological-phonon candidates.

The database also identified 322 clean systems with isolated topological features, turning individual predictions into a reusable experimental discovery platform.

HT-TPHONON
10,000+ materials
Open database

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Graphene · Brillouin zone

Γclosed phonon crossing

Original concept illustration: a nodal ring encircling Γ in graphene's phonon spectrum.

03 Physical Review B · 2020

Graphene as a theory target for phonon topology.

First-principles calculations identified four classes of Dirac phonons, a Γ-centered LA–ZO nodal ring, and nontrivial edge states in a material whose lattice dynamics can be measured with exceptional momentum resolution.

Those predictions were subsequently tested by full-zone HREELS in the 2023 PRL experiment above, which mapped the ring and associated Dirac crossings and additionally resolved a second TA–ZO nodal ring.

First principles
Dirac phonons
Edge spectra

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Multi-component Weyl phonons−1

+2bulk nodes → surface arcs

Original concept illustration: coexisting Weyl phonons with distinct degeneracies and topological charges.

04 Physical Review B · 2018

New phonon quasiparticles in real crystals.

Calculations for TiS, ZrSe, and HfTe predicted coexisting three-component and two-component Weyl phonons, together with surface arcs that encode their bulk topological charges.

The study established a symmetry-based design language for unconventional lattice excitations and showed that multiple kinds of Weyl phonons can coexist in one materials family.

Weyl phonons
Crystal symmetry
Surface arcs

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Continue across the research program.

Phonons connect naturally to correlated electrons, superconductivity, and learned multiscale models.

Research direction 02Electrons Research direction 03Machine learning

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