Visibility of the amplitude (Higgs) mode in condensed matter
By D. Podolsky, A. Auerbach, D. Arovas. 2011
144 citations recorded by the source corpus.
The amplitude mode is a ubiquitous collective excitation in condensed-matter systems with broken continuous symmetry. It is expected in antiferromagnets, short coherence length superconductors, charge density waves, and lattice Bose condensates. Its detection is a valuable test of the corresponding field theory, and its mass gap measures the proximity to a quantum critical point. However, since the amplitude mode can decay into low-energy Goldstone modes, its experimental visibility has been questioned. Here we show that the visibility dependsonthesymmetryofthemeasuredsusceptibility.Thelongitudinalsusceptibilitydivergesatlowfrequency as Im χ σσ ∼ ω −1 (d = 2) or log(1/|ω| )( d = 3), which can completely obscure the amplitude peak. In contrast, the scalar susceptibility is suppressed by four extra powers of frequency, exposing the amplitude peak throughout the ordered phase. We discuss experimental setups for measuring the scalar susceptibility. The conductivity of the O(2) theory (relativistic superfluid) is a scalar response and therefore exhibits suppressed absorption below the Higgs mass threshold, σ ∼ ω 2d+1 . In layered, short coherence length superconductors, (relevant, e.g., to cuprates) this threshold is raised by the interlayer plasma frequency.
Subfields: Atomic and Molecular Physics, and Optics, Condensed Matter Physics
View Paper: https://www.semanticscholar.org/paper/e3105f628078c3b9735fd981730ed5fdeec17063
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In Atomic and Molecular Physics, and Optics
In Condensed Matter Physics
Citations in the corpus
- The Higgs mode in disordered superconductors close to a quantum phase transition (2014, background): “How would the Higgs mode contribute to the dynamical conductivity? Theoretically it is predicted to give rise to excess conductivity at sub-gap frequencies [12] which we will refer to as Higgs conductivity, σ̂(ω), in the remainder of the paper.”
- The nonperturbative functional renormalization group and its applications (2020, methodology): “In the ordered phase of the two-dimensional O(2) and O(3) models, the “Higgs” amplitude mode, whose existence and visibility in the vicinity of the quantum critical point have been overlooked for a long time [536], is well described by FRG [220, 537], in quantitative agreement with Monte Carlo simul”