Coherent spectroscopy of collective excitations in superfluid helium far from equilibrium

Fuente: arXiv
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Autores principales: Voith, Gabriel, Milner, Alexander A., Milner, Valery
Formato: Preprint
Publicado: 2026
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author Voith, Gabriel
Milner, Alexander A.
Milner, Valery
author_facet Voith, Gabriel
Milner, Alexander A.
Milner, Valery
contents Ultrafast dynamics of collective excitations in superfluids remains largely unexplored beyond the roton regime, despite its importance for understanding nonequilibrium processes in these systems. Here, we employ ultrafast coherent control with sequences of femtosecond pulses to perform spectroscopy of multiple branches of the Landau excitation spectrum in superfluid helium far from equilibrium. By measuring the time-resolved optical birefringence, we track the nonequilibrium dynamics of maxon pairs and Pitaevskii plateau excitations alongside the previously studied roton pairs, revealing surprisingly strong binding energy of maxon pairs, their extremely short lifetime, and the influence of the quasiparticle effective mass on the phase of the coherent response. These results demonstrate the ability to extract previously inaccessible information about collective excitations in a strongly interacting quantum fluid by probing its nonequilibrium dynamics on femtosecond and picosecond timescales.
format Preprint
id arxiv_https___arxiv_org_abs_2605_17835
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Coherent spectroscopy of collective excitations in superfluid helium far from equilibrium
Voith, Gabriel
Milner, Alexander A.
Milner, Valery
Other Condensed Matter
Quantum Gases
Quantum Physics
Ultrafast dynamics of collective excitations in superfluids remains largely unexplored beyond the roton regime, despite its importance for understanding nonequilibrium processes in these systems. Here, we employ ultrafast coherent control with sequences of femtosecond pulses to perform spectroscopy of multiple branches of the Landau excitation spectrum in superfluid helium far from equilibrium. By measuring the time-resolved optical birefringence, we track the nonequilibrium dynamics of maxon pairs and Pitaevskii plateau excitations alongside the previously studied roton pairs, revealing surprisingly strong binding energy of maxon pairs, their extremely short lifetime, and the influence of the quasiparticle effective mass on the phase of the coherent response. These results demonstrate the ability to extract previously inaccessible information about collective excitations in a strongly interacting quantum fluid by probing its nonequilibrium dynamics on femtosecond and picosecond timescales.
title Coherent spectroscopy of collective excitations in superfluid helium far from equilibrium
topic Other Condensed Matter
Quantum Gases
Quantum Physics
url https://arxiv.org/abs/2605.17835