Amplitude Higgs Mode and Admittance in Superconductors with a Moving Condensate

• Published in: Physical review letters Vol. 118; no. 4; p. 047001
• Main Authors: Moor, Andreas, Volkov, Anatoly F, Efetov, Konstantin B
• Format: Journal Article
• Language: English
• Published: United States 27.01.2017
• ISSN: 1079-7114
• DOI: 10.1103/PhysRevLett.118.047001

We consider the amplitude (Higgs) mode in a superconductor with a condensate flow (supercurrent). We demonstrate that, in this case, the amplitude mode corresponding to oscillations δ|Δ|_{Ω}exp(iΩt) of the superconducting gap is excited by an external ac electric field E_{Ω}exp(iΩt) already in the first order in |E_{Ω}|, so that δ|Δ|_{Ω}∝(v_{0}E_{Ω}), where v_{0} is the velocity of the condensate. The frequency dependence δ|Δ|_{Ω} has a resonance shape with a maximum at Ω=2Δ. In contrast to the standard situation without the condensate flow, the oscillations of the amplitude δ|Δ(t)| contribute to the admittance Y_{Ω}. We provide a formula for admittance of a superconductor with a supercurrent. The predicted effect opens new ways of experimental investigation of the amplitude mode in superconductors and materials with superconductivity competing with other states.