Are Tkachenko Modes Overdamped? A Microscopic Resolution

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Abstract
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Tkachenko modes are the softest collective excitations of the vortex lattice in a rapidly rotating Bose–Einstein condensate, and their lifetime has long been disputed: microscopic calculations predict strong damping at low energy, while symmetry arguments imply the mode becomes increasingly sharp. I will present a lowest-Landau-level calculation that resolves the discrepancy. A cancellation eliminates the leading decay process, leaving a damping rate strongly suppressed at low energy. The surviving channel turns out to be unexpectedly sensitive to the sixfold lattice anisotropy, which enhances the rate without changing its scaling. The result explains microscopically why Tkachenko modes remain well-defined quasiparticles at low energy.

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About the Speaker
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Dr. Dung Xuan Nguyen is Head of the Quantum Physics Group and Senior Researcher at the International Centre for Interdisciplinary Science and Education (ICISE) in Quy Nhơn, Vietnam. He received his B.S. from Hanoi University of Science in 2007, his M.S. from KAIST in 2010, and his Ph.D. in Physics from the University of Chicago in 2017 under the supervision of Dam Thanh Son. He was subsequently a postdoctoral researcher at the Rudolf Peierls Centre for Theoretical Physics, University of Oxford (2017–2019), and at the Brown Theoretical Physics Center, Brown University (2019–2022), then Junior Team Leader and Senior Researcher at the IBS Center for Theoretical Physics of Complex Systems in South Korea (2022–2025), holding a concurrent appointment as Associate Professor at the University of Science and Technology, Korea (2023–2025). He joined ICISE in 2025. His research is in theoretical condensed matter physics, with a focus on the fractional quantum Hall effect and the topological and geometric properties of strongly correlated systems, including the prediction of the emergent graviton mode and the Raman scattering probe that detects it, as well as fracton-elasticity duality, vortex crystals in rotating superfluids, and topological photonics.