Higgs-mode resonance in third harmonic generation in NbN superconductors: Multiband electron-phonon coupling, impurity scattering, and polarization-angle dependence
We theoretically investigate the resonance of third harmonic generation (THG) that has been observed at frequency being half of the superconducting gap in a multiband disordered superconductor NbN. The central question is whether the dominant contribution to the THG resonance comes from the Higgs mo...
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| Format: | Article |
| Language: | English |
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American Physical Society
2020-10-01
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| Series: | Physical Review Research |
| Online Access: | http://doi.org/10.1103/PhysRevResearch.2.043029 |
| _version_ | 1797211290597326848 |
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| author | Naoto Tsuji Yusuke Nomura |
| author_facet | Naoto Tsuji Yusuke Nomura |
| author_sort | Naoto Tsuji |
| collection | DOAJ |
| description | We theoretically investigate the resonance of third harmonic generation (THG) that has been observed at frequency being half of the superconducting gap in a multiband disordered superconductor NbN. The central question is whether the dominant contribution to the THG resonance comes from the Higgs mode (the collective amplitude mode of the superconducting order parameter) or quasiparticle excitations. To resolve this issue, we analyze a realistic three-band model with effective intraband and interband phonon-mediated interactions together with nonmagnetic impurity scatterings. Using the first-principles estimate of the ratio between the intraband and interband pairing interactions with multiband impurity scattering rates being varied from clean to dirty regimes, we calculate the THG susceptibility for NbN in a channel-resolved manner by means of the BCS and self-consistent Born approximations. In the dirty regime, which is close to the experimental situation, the leading contribution is given by the paramagnetic channel of the Higgs mode having almost no polarization-angle dependence, while the second leading contribution comes from the paramagnetic channel of quasiparticles generally showing significant polarization-angle dependence. The result is consistent with the recent experimental observation of no polarization-angle dependence of THG, giving firm evidence that the Higgs mode dominantly contributes to the THG resonance in NbN superconductors. |
| first_indexed | 2024-04-24T10:24:08Z |
| format | Article |
| id | doaj.art-c00fb2a6fb8e4f9681870f2b91979e63 |
| institution | Directory Open Access Journal |
| issn | 2643-1564 |
| language | English |
| last_indexed | 2024-04-24T10:24:08Z |
| publishDate | 2020-10-01 |
| publisher | American Physical Society |
| record_format | Article |
| series | Physical Review Research |
| spelling | doaj.art-c00fb2a6fb8e4f9681870f2b91979e632024-04-12T17:01:55ZengAmerican Physical SocietyPhysical Review Research2643-15642020-10-012404302910.1103/PhysRevResearch.2.043029Higgs-mode resonance in third harmonic generation in NbN superconductors: Multiband electron-phonon coupling, impurity scattering, and polarization-angle dependenceNaoto TsujiYusuke NomuraWe theoretically investigate the resonance of third harmonic generation (THG) that has been observed at frequency being half of the superconducting gap in a multiband disordered superconductor NbN. The central question is whether the dominant contribution to the THG resonance comes from the Higgs mode (the collective amplitude mode of the superconducting order parameter) or quasiparticle excitations. To resolve this issue, we analyze a realistic three-band model with effective intraband and interband phonon-mediated interactions together with nonmagnetic impurity scatterings. Using the first-principles estimate of the ratio between the intraband and interband pairing interactions with multiband impurity scattering rates being varied from clean to dirty regimes, we calculate the THG susceptibility for NbN in a channel-resolved manner by means of the BCS and self-consistent Born approximations. In the dirty regime, which is close to the experimental situation, the leading contribution is given by the paramagnetic channel of the Higgs mode having almost no polarization-angle dependence, while the second leading contribution comes from the paramagnetic channel of quasiparticles generally showing significant polarization-angle dependence. The result is consistent with the recent experimental observation of no polarization-angle dependence of THG, giving firm evidence that the Higgs mode dominantly contributes to the THG resonance in NbN superconductors.http://doi.org/10.1103/PhysRevResearch.2.043029 |
| spellingShingle | Naoto Tsuji Yusuke Nomura Higgs-mode resonance in third harmonic generation in NbN superconductors: Multiband electron-phonon coupling, impurity scattering, and polarization-angle dependence Physical Review Research |
| title | Higgs-mode resonance in third harmonic generation in NbN superconductors: Multiband electron-phonon coupling, impurity scattering, and polarization-angle dependence |
| title_full | Higgs-mode resonance in third harmonic generation in NbN superconductors: Multiband electron-phonon coupling, impurity scattering, and polarization-angle dependence |
| title_fullStr | Higgs-mode resonance in third harmonic generation in NbN superconductors: Multiband electron-phonon coupling, impurity scattering, and polarization-angle dependence |
| title_full_unstemmed | Higgs-mode resonance in third harmonic generation in NbN superconductors: Multiband electron-phonon coupling, impurity scattering, and polarization-angle dependence |
| title_short | Higgs-mode resonance in third harmonic generation in NbN superconductors: Multiband electron-phonon coupling, impurity scattering, and polarization-angle dependence |
| title_sort | higgs mode resonance in third harmonic generation in nbn superconductors multiband electron phonon coupling impurity scattering and polarization angle dependence |
| url | http://doi.org/10.1103/PhysRevResearch.2.043029 |
| work_keys_str_mv | AT naototsuji higgsmoderesonanceinthirdharmonicgenerationinnbnsuperconductorsmultibandelectronphononcouplingimpurityscatteringandpolarizationangledependence AT yusukenomura higgsmoderesonanceinthirdharmonicgenerationinnbnsuperconductorsmultibandelectronphononcouplingimpurityscatteringandpolarizationangledependence |