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Kawano, H.; Yoshizawa, H.; Takeya, Hiroyuki; Kadowaki, K.

doi:10.1103/physrevlett.77.4628

Cited by 90 publications

(77 citation statements)

References 24 publications

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“…In the normal state, on the other hand, the phonon spectrum exhibits an almost symmetric single peak with a low-energy tail, and the renormalized phonon frequency is softened by the el-ph coupling [34,39]. These features in the phonon spectra have indeed been experimentally observed in some strongly coupled SCs [44][45][46][47][48], and theoretically explained as an effect of the phonon self-energy [49] (phonon anomaly).…”

Section: A Dynamical Pair Susceptibility and Collective Amplitude Modesmentioning

confidence: 66%

Multiple amplitude modes in strongly coupled phonon-mediated superconductors

et al. 2016

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We study collective amplitude modes of the superconducting order parameter in strongly coupled electronphonon systems described by the Holstein model using the nonequilibrium dynamical mean-field theory with the self-consistent Migdal approximation as an impurity solver. The frequency of the Higgs amplitude mode is found to coincide with the superconducting gap even in the strongly coupled (beyond BCS) regime. Besides the Higgs mode, we find another collective mode involving the dynamics of both the phonons and the superconducting order parameter. The frequency of this mode, higher than twice the renormalized phonon frequency in the superconducting phase, is shown to reflect a strong electron-mediated phonon-phonon interaction. Both of collective modes are predicted to contribute to time-resolved photoemission spectra after a strong laser pump as vertex corrections to produce resonance peaks, which allows one to distinguish them from quasiparticle excitations.

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Section: A Dynamical Pair Susceptibility and Collective Amplitude Modesmentioning

confidence: 66%

Multiple amplitude modes in strongly coupled phonon-mediated superconductors

et al. 2016

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“…As mentioned in the introduction, phonon studies of YNi 2 B 2 C focused on the dramatic superconductivity-induced changes of the line shape of the TA mode at q = (0.5, 0, 0) [4,31] and, hence, only the dispersion curves of this TA and the first TO modes were reported for the normal state [32,33].…”

Section: V1 Phonon Dispersionsmentioning

confidence: 99%

“…In order to perform a more detailed check of current calculations we embarked on a comprehensive investigation of the phonon properties of YNi 2 B 2 C using both DFPT calculations and inelastic neutron scattering. We note that we have chosen YNi 2 B 2 C (T c = 15.2 K) and not YPd 2 B 2 C (T c =23K [8]) -which has a higher T c -for our study for the simple reason that there are no single crystals available for YPd 2 B 2 C. YNi 2 B 2 C has been already investigated by two other groups [4,30] but only with a very limited scope, i.e. to study the temperature dependence of a a pronounced phonon anomaly in a transverse acoustic branch across the superconducting transition.…”

Section: Introductionmentioning

confidence: 99%

Phonons and electron-phonon coupling in YNi2B2C

et al. 2014

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We present a combined density-functional-perturbation-theory and inelastic neutron scattering study of the lattice dynamical properties of YNi 2 B 2 C. In general, very good agreement was found between theory and experiment for both phonon energies and line widths. Our analysis reveals that the strong coupling of certain low energy modes is linked to the presence of large displacements of the light atoms, i.e. B and C, which is unusual in view of the rather low phonon energies. Specific modes exhibiting a strong coupling to the electronic quasiparticles were investigated as a function of temperature. Their energies and line widths showed marked changes on cooling from room temperature to just above the superconducting transition at T c = 15.2 K. Calculations simulating the effects of temperature allow to model the observed temperature dependence qualitatively.

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“…Though this deviation may be attributed to the low-energy optical phonons, it is not clear where they originate from [20]. Moreover, recent inelastic neutron scattering experiments demonstrated an anomalous phonon branch which strongly couples to the electronic excitation in the superconducting state [21]. Therefore, the quantitative analysis of the T -dependence of the electronic contribution obtained by subtracting the phonon terms from the total heat capacity is precarious.…”

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confidence: 99%