2008/06/21 by I. Tornes, D. Stroud
Computer Science · Physics and Astronomy · #Absorption (acoustics) #Amplitude #Atomic physics #Biasing #Condensed matter physics #Excited state #Josephson effect #Mechanical and Optical Resonators #Microwave #Omega #Optics #Physics #Quantum Information and Cryptography #Quantum and electron transport phenomena #Quantum mechanics #Superconductivity #Voltage #cond-mat.mes-hall #cond-mat.supr-con
paper · pdf · doi:10.1103/physrevb.77.224513
15 pages, 13 figures, accepted for publication in Physical Review B
arxiv created 2008/06/21 · openalex publication_date 2008/06/27 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
We present a simple model to describe multiphoton transitions between the quasi-bound states of a current-driven Josephson junction. The transitions are induced by applying an ac voltage with controllable frequency and amplitude across the junction. The voltage induces transitions across the junction when the frequency \ensuremathω satisfies n\ensuremathℏ\ensuremathω=\ensuremathΔE10, where \ensuremathΔE10 is the splitting between the ground and first excited quasi-bound state of the junction. We calculate the matrix elements of the transitions as a function of the dc bias current I, and the frequency \ensuremathω and amplitude Vac of the microwave voltage, for representative junction parameters. We also calculate the frequency-dependent absorption coefficient by solving the relevant Bloch equations when the ac voltage is sufficiently weak. In this regime, the absorption coefficient is a sum of Lorentzian lines centered at the n-photon absorption frequency, of strength proportional to the squared matrix elements. For fixed Vac, the transition rate for an n-photon process usually decreases with increasing n. We also find a characteristic even-odd effect: The absorption coefficient typically increases with I for n even but decreases for n odd. Our results agree qualitatively with recent experiments.