Higgs mode in a strongly interacting fermionic superfluid

Behrle, Alexandra; Harrison, Timothy; Kombe, Johannes; Gao, Kaixiong; Link, M.; Bernier, Jean-Sébastien; Kollath, Corinna; Köhl, M.

doi:10.1038/s41567-018-0128-6

Cited by 97 publications

(81 citation statements)

References 39 publications

(57 reference statements)

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“…We finally note the interesting question concerning the impact of imbalance on damping of the amplitude mode, whose existence was recently experimentally established. 34,[66][67][68][69]…”

Section: Discussionmentioning

confidence: 99%

Damping of the Anderson-Bogolyubov mode in Fermi mixtures by spin and mass imbalance

Zdybel

Jakubczyk

2019

Phys. Rev. A

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We study the temporally nonlocal contributions to the gradient expansion of the pair fluctuation propagator for spin-and mass-imbalanced Fermi mixtures. These terms are related to damping processes of sound-like (Anderson-Bogolyubov) collective modes and are relevant for the structure of the complex pole of the pair fluctuation propagator. We derive conditions under which damping occurs even at zero temperature for large enough mismatch of the Fermi surfaces. We compare our analytical results with numerically computed damping rates of the Anderson-Bogolyubov mode. arXiv:1908.08559v1 [cond-mat.quant-gas]

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“…We finally note the interesting question concerning the impact of imbalance on damping of the amplitude mode, whose existence was recently experimentally established. 34,[66][67][68][69]…”

Section: Discussionmentioning

confidence: 99%

Damping of the Anderson-Bogolyubov mode in Fermi mixtures by spin and mass imbalance

Zdybel

Jakubczyk

2019

Phys. Rev. A

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“…9(c) compares the results of the GMB-plus-Popov (full line) and Popov (broken line) calculations at T = 0 with the experimental data from Ref. [51] (triangles), which are taken at the nominal temperature T /T F = 0.07 ± 0.02. This set of experimental data appears to agree quite well with the Popov calculation, while discrepancies appear when compared with the GMB-plus-Popov calculation.…”

Section: Gap Parameter Throughout the Bcs-becmentioning

confidence: 98%

“…[50] measures a response (density-density correlation) function in the linear regime for which the system is probed at thermodynamic equilibrium, Ref. [51] adopts a time-dependent protocol that brings the system out of thermodynamic equilibrium. This may give rise to a retardation mechanism, whereby increasingly complicated many body-processes (like the GMB contribution) could take longer time than simpler processes (like the Popov one) before being excited by the experimental protocol, in analogy to what occurs in the context of the orthogonality catastrophe [52].…”

Section: Gap Parameter Throughout the Bcs-becmentioning

confidence: 99%

Gap equation with pairing correlations beyond the mean-field approximation and its equivalence to a Hugenholtz-Pines condition for fermion pairs

2018

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The equation for the gap parameter represents the main equation of the pairing theory of superconductivity. Although it is formally defined through a single-particle property, physically it reflects the pairing correlations between opposite-spin fermions. Here, we exploit this physical connection and cast the gap equation in an alternative form which explicitly highlights these two-particle correlations, by showing that it is equivalent to a Hugenholtz-Pines condition for fermion pairs. At a formal level, a direct connection is established in this way between the treatment of the condensate fraction in condensate systems of fermions and bosons. At a practical level, the use of this alternative form of the gap equation is expected to make easier the inclusion of pairing fluctuations beyond mean field. As a proof-of-concept of the new method, we apply the modified form of the gap equation to the long-pending problem about the inclusion of the Gorkov-Melik-Barkhudarov correction across the whole BCS-BEC crossover, from the BCS limit of strongly overlapping Cooper pairs to the BEC limit of dilute composite bosons, and for all temperatures in the superfluid phase. Our numerical calculations yield excellent agreement with the recently determined experimental values of the gap parameter for an ultra-cold Fermi gas in the intermediate regime between BCS and BEC, as well as with the available quantum Monte Carlo data in the same regime.

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“…Two particular excitations are Higgs and Goldstone modes, which correspond to the modulation of the amplitude and phase of an order parameter that breaks a continuous symmetry. Originally discussed in the context of particle physics [2] and superconductivity [3], Higgs and Goldstone excitations were found in cold atom systems, such as superfluids [4][5][6][7][8] or supersolids [9]. Higgs and Goldstone modes are well-studied in superconductors today [10][11][12][13][14][15][16][17][18][19][20][21], and similar manifestations have recently been reported in charge density wave (CDW) systems [22][23][24], antiferromagnets [25][26][27], and excitonic insulators [28].…”

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confidence: 95%

Parametric Excitation of an Optically Silent Goldstone-Like Phonon Mode

2020

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It has recently been indicated that the hexagonal manganites exhibit Higgs-and Goldstone-like phonon modes that modulate the amplitude and phase of their primary order parameter. Here, we describe a mechanism by which a silent Goldstone-like phonon mode can be coherently excited, which is based on nonlinear coupling to an infrared-active Higgs-like phonon mode. Using a combination of first-principles calculations and phenomenological modeling, we describe the coupled Higgs-Goldstone dynamics in response to the excitation with a terahertz pulse. Besides theoretically demonstrating coherent control of crystallographic Higgs and Goldstone excitations, we show that the previously inaccessible silent phonon modes can be excited coherently with this mechanism.Order parameters are physical observables that are used to quantify the different states of matter. Their amplitudes and phases can be excited by external stimuli, such as a laser pulse, leading to exotic states of matter that cannot be accessed in equilibrium [1]. Two particular excitations are Higgs and Goldstone modes, which correspond to the modulation of the amplitude and phase of an order parameter that breaks a continuous symmetry. Originally discussed in the context of particle physics [2] and superconductivity [3], Higgs and Goldstone excitations were found in cold atom systems, such as superfluids [4][5][6][7][8] or supersolids [9]. Higgs and Goldstone modes are well-studied in superconductors today [10][11][12][13][14][15][16][17][18][19][20][21], and similar manifestations have recently been reported in charge density wave (CDW) systems [22][23][24], antiferromagnets [25][26][27], and excitonic insulators [28]. It has been debated whether the optical and acoustic vibrational modes of solids can be considered Higgs and Goldstone excitations of the crystal lattice [29]. Several complex transition metal oxide compounds have shown signatures of optical Goldstone-like phonon modes that live in their symmetry-broken potential energy landscape [30][31][32][33][34].Coherent control over Raman-active phonons via impulsive stimulated Raman scattering using visible light pulses is well-established [35,36]. Recently, the excitation of infrared (IR)-active phonons with large amplitudes via IR absorption has become feasible through the development of high intensity terahertz and mid-IR sources. This progress has enabled selective control over the dynamics of the crystal lattice through nonlinear phonon interactions using ionic Raman scattering [37-39] and two-particle absorption mechanisms [40][41][42][43][44][45]. In contrast, phonon modes that do not respond to IR absorption or Raman scattering techniques, so called silent modes, can only be detected through hyper-Raman scattering. As hyper-Raman scattering is a third-order interaction of the electric field component of light with a * djuraschek@seas.harvard.edu † prineha@seas.harvard.edu phonon mode, it is inefficient and no coherent excitation has been achieved yet. Higgs and Goldstone modes, similar to silent p...

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Higgs mode in a strongly interacting fermionic superfluid

Cited by 97 publications

References 39 publications

Damping of the Anderson-Bogolyubov mode in Fermi mixtures by spin and mass imbalance

Damping of the Anderson-Bogolyubov mode in Fermi mixtures by spin and mass imbalance

Gap equation with pairing correlations beyond the mean-field approximation and its equivalence to a Hugenholtz-Pines condition for fermion pairs

Parametric Excitation of an Optically Silent Goldstone-Like Phonon Mode

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