Lin and Goldman Reply:

Lin, Yen-Hsiang; Goldman, A. M.

doi:10.1103/physrevlett.108.159702

Cited by 58 publications

(113 citation statements)

References 3 publications

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“…For d-wave superconductors such as high-T c cuprates, it has been group-theoretically shown 21 that they can accommodate additional amplitude (Higgs) modes coming from multiple irreducible representations of the k-dependent gap function with the D 4 point-group symmetry. As for the phase modes, multi-gap superconductors are predicted to have an out-of-phase mode between the two components of the gap function [22][23][24][25][26][27][28][29][30] , called "Leggett mode".…”

Section: Introductionmentioning

confidence: 99%

Theory of light-induced resonances with collective Higgs and Leggett modes in multiband superconductors

2017

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We theoretically investigate coherent optical excitations of collective modes in two-band BCS superconductors, which accommodate two Higgs modes and one Leggett mode corresponding, respectively, to the amplitude and relative-phase oscillations of the superconducting order parameters associated with the two bands. We find, based on a mean-field analysis, that each collective mode can be resonantly excited through a nonlinear light-matter coupling when the doubled frequency of the driving field coincides with the frequency of the corresponding mode. Among the two Higgs modes, the higher-energy one exhibits a sharp resonance with light, while the lower-energy mode has a broadened resonance width. The Leggett mode is found to be resonantly induced by a homogeneous ac electric field because the leading nonlinear effect generates a potential offset between the two bands that couples to the relative phase of the order parameters. The resonance for the Leggett mode becomes sharper with increasing temperature. All of these light-induced collective modes along with density fluctuations contribute to the third-harmonic generation. We also predict an experimental possibility of optical detection of the Leggett mode.

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Section: Introductionmentioning

confidence: 99%

Theory of light-induced resonances with collective Higgs and Leggett modes in multiband superconductors

2017

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“…A three-band version of this model has been has been considered in Refs. 15,[18][19][20][21]23). The interaction U hh gives rise to +− gaps on the two GCP's, while U he gives rise to an s± state with different signs of the gaps on the two hole pockets.…”

Section: Introductionmentioning

confidence: 99%

s+isstate with broken time-reversal symmetry in Fe-based superconductors

2013

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We analyze the evolution of the superconducting gap structure in strongly hole doped Ba1−xKxFe2As2 between x = 1 and x ∼ 0.4 (optimal doping). In the latter case, the pairing state is most likely s±, with different gap signs on hole and electron pockets, but with the same signs of the gap on the two Γ-centered hole pockets (a ++ state on hole pockets). In a pure KFe2As2 (x = 1), which has only hole pockets, laser ARPES data suggested another s± state, in which the gap changes sign between hole pockets (a +− state). We analyze how ++ gap transforms into a +− gap as x → 1. We found that this transformation occurs via an intermediate s + is, state in which the gaps on the two hole pockets differ in phase by φ, which gradually involves from φ = π (the +− state) to φ = 0 (the ++ state). This state breaks time-reversal symmetry and has huge potential for applications. We compute the dispersion of collective excitations and show that two different Leggett-type phase modes soften at the two end points of TRSB state.

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“…Comparing Fig.4 (c) with Fig.4 (d), the spectral weight of Leggett mode diminishes after merging into the continuum. Investigations of the Leggett modes in multi-band superconductor have already attracted intensive interests [24][25][26][27][28][29]. It is only until very recently years that some evidences of its existence have been observed experimentally in multi-band superconductors MgB 2 , by tunneling spectroscopy techniques [30], Raman spectroscopy [31], and angle-resolved photoemission spectroscopy [32].…”

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confidence: 99%

Collective modes in a two-band superfluid of ultracold alkaline-earth-metal atoms close to an orbital Feshbach resonance

2017

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We discuss the collective modes in an alkaline-earth Fermi gas close to an orbital Feshbach resonance. Unlike the usual Feshbach resonance, the orbital Feshbach resonance in alkaline-earth atoms realizes a two-band superfluid system where the fermionic nature of both the open and the closed channel has to be taken into account. We show that apart from the usual Anderson-Bogoliubov mode which corresponds to the oscillation of total density, there also appears the long-sought Leggett mode corresponding to the oscillation of relative density between the two channels. The existence of the phonon and the Leggett modes and their evolution are discussed in detail. We show how these collective modes are reflected in the density response of the system. [5][6][7], is that there are two clock states, the electronic s-and p-states, both of which have zero electronic angular momentum J = 0. As a result, there is no hyperfine coupling between the electronic and nuclear spins. The inter-atomic interactions which depend (primarily) on the electronic configurations thus become independent of nuclear spins. This realizes the so-called SU (N ) symmetries, where N is the number of nuclear spin components [8][9][10][11][12][13][14][15]. The OFR relies on the atoms residing on both the s and p-states which possess slight different Landé g-factors [16,17], thus allowing tuning by external magnetic field.

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Lin and Goldman Reply:

Cited by 58 publications

References 3 publications

Theory of light-induced resonances with collective Higgs and Leggett modes in multiband superconductors

Theory of light-induced resonances with collective Higgs and Leggett modes in multiband superconductors

s+isstate with broken time-reversal symmetry in Fe-based superconductors

Collective modes in a two-band superfluid of ultracold alkaline-earth-metal atoms close to an orbital Feshbach resonance

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