Energy<i>vs</i>Momentum Relation for the Excitations in Liquid Helium

Yarnell, J. L.; Arnold, G.; Bendt, P.J.; Kerr, E.C.

doi:10.1103/physrevlett.1.9

Cited by 36 publications

(20 citation statements)

References 7 publications

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“…In chargedensity wave compounds, a persisting Higgs mode has been observed as a well-defined resonance [7][8][9]. In superfluid Helium [10] and Bose-Einstein condensates [11] * donner@phys.ethz.ch Higgs and Goldstone modes for a U(1) symmetry. Effective potential across the phase transition as a function of the order parameter α = α1 +iα2 = |α|e iφ .…”

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Monitoring and manipulating Higgs and Goldstone modes in a supersolid quantum gas

Léonard

Morales

Zupancic

et al. 2017

Science

170

142

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Access to collective excitations lies at the heart of our understanding of quantum many-body systems. We study the Higgs and Goldstone modes in a supersolid quantum gas that is created by coupling a Bose-Einstein condensate symmetrically to two optical cavities. The cavity fields form a U(1)-symmetric order parameter that can be modulated and monitored along both quadratures in real time. This enables us to measure the excitation energies across the superfluid-supersolid phase transition, establish their amplitude and phase nature, as well as characterize their dynamics from an impulse response. Furthermore, we can give a tunable mass to the Goldstone mode at the crossover between continuous and discrete symmetry by changing the coupling of the quantum gas with either cavity.Collective excitations are crucial for describing the dynamics of quantum many-body systems. They provide unified explanations of phenomena studied in different disciplines of physics, such as in condensed matter [1] or particle physics [2], or in cosmology [3]. The symmetry of the underlying effective Hamiltonian determines the character of the excitations, which changes in a fundamental way when a continuous symmetry is broken at a phase transition. Excitations can now appear both at finite and zero energy.In the paradigmatic case of models with U(1)-symmetry breaking, the system can be described by a complex scalar order parameter in an effective potential as illustrated in Fig. 1(A-B) [4]. In the normal phase, the potential is bowl-shaped with a single minimum at vanishing order parameter, and correspondingly two orthogonal amplitude excitations. Within the ordered phase, the potential shape changes to a 'sombrero' with an infinite number of minima on a circle. Here, fluctuations of the order parameter reveal two different excitations: a Higgs (or amplitude) mode, which stems from amplitude fluctuations of the order parameter and shows a finite excitation energy, and a Goldstone (or phase) mode, which stems from phase fluctuations of the order parameter and has zero excitation energy. The former should yield correlated fluctuations in the two squared quadratures of the order parameter, whereas the latter should show anticorrelated behavior.Condensed matter systems typically do not provide access to both quadratures of the order parameter, and Higgs and Goldstone modes have to be excited and detected by incoherent processes. In addition, the idealized situation is often disguised by further interactions that reduce the number of distinct modes [1, 6]. For charged particles, the minimal coupling to a vector potential can even completely suppress the Goldstone mode through the Anderson-Higgs mechanism [2]. In chargedensity wave compounds, a persisting Higgs mode has been observed as a well-defined resonance [7][8][9]. In superfluid Helium [10] and Bose-Einstein condensates [11] * donner@phys.ethz.ch Illustration of the experiment. A Bose-Einstein condensate (blue stripes) cut into slices by a transverse pump lattice potential (red stripes)...

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confidence: 99%

Monitoring and manipulating Higgs and Goldstone modes in a supersolid quantum gas

Léonard

Morales

Zupancic

et al. 2017

Science

170

142

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“…On the basis of P-R modes, Landau constructed a theory of superfluidity so successful that other theories and BEC were largely forgotten. Feynman and Cohen [6] developed a microscopic theory of P-R modes which were eventually observed [7][8][9]. Modern measurements [10][11][12][13][14][15] show that in bulk liquid 4 He welldefined P-R modes (see Fig.…”

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Evidence for a Common Physical Origin of the Landau and BEC Theories of Superfluidity

Diallo¹,

Azuah²,

Abernathy³

et al. 2014

Phys. Rev. Lett.

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“…At N 0 N, the Bogoliubov neglects the term of the density operator describing atoms above the condensatẽ % %p p in [4], thus reducing the operator% %p p tô % %p p N 0 p â a ÿp p â ap p :…”

Section: Discussionmentioning

confidence: 99%

“…In 1938, London [1] was the first to propose the model of superfluid liquid 4 He as an ideal Bose gas of atoms. Landau [2], on the other hand, advanced a different model where he predicted that the thermodynamic properties of superfluid liquid 4 He can be described, using the notation of collective excitations which he called phonons and rotons, which are excited in low-and high-momenta regions, respectively.…”

Section: Introductionmentioning

confidence: 99%

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Two Types of Quasiparticles Excited in a Bose Gas

Minasyan

Touryan

2003

Phys. Rev. Lett.

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We present a novel approach for investigating the superfluid liquid 4He based on the proper use of the nonideal Bose gas model for dilute hard spheres. The results show that the presence of a macroscopic number of condensate atoms leads to the existence of a nonphysical branch, corresponding to density excitations, in addition to the continuous branch of the phonon-maxon-roton excitation spectrum.

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EnergyvsMomentum Relation for the Excitations in Liquid Helium

Cited by 36 publications

References 7 publications

Monitoring and manipulating Higgs and Goldstone modes in a supersolid quantum gas

Monitoring and manipulating Higgs and Goldstone modes in a supersolid quantum gas

Evidence for a Common Physical Origin of the Landau and BEC Theories of Superfluidity

Two Types of Quasiparticles Excited in a Bose Gas

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