Andreev interferometers in a strong radio-frequency field

Area of Science:

• Condensed Matter Physics
• Quantum Phenomena
• Mesoscopic Physics

Background:

• Superconducting loops (Andreev interferometers) exhibit phase-periodic resistance oscillations influenced by magnetic flux.
• Understanding the impact of external radiation on quantum interference effects is crucial for developing novel electronic devices.

Purpose of the Study:

• To experimentally investigate the influence of 1-40 GHz radio-frequency (RF) radiation on the resistance of normal-superconducting mesoscopic conductors.
• To analyze the changes in superconducting phase-periodic resistance oscillations under varying RF amplitudes and frequencies.

Main Methods:

• Experimental study of normal (N) mesoscopic conductors coupled to superconducting (S) loops (Andreev interferometers).
• Application of 1-40 GHz radio-frequency (RF) radiation with varying amplitudes.
• Measurement of resistance oscillations as a function of applied magnetic flux and RF amplitude.

Main Results:

• At low RF amplitudes, standard h/2e superconducting phase periodic resistance oscillations were observed.
• With increasing RF amplitude, these oscillations exhibited a π-shift, and resistance became an oscillating function of RF amplitude.
• The response time of the Andreev interferometer was estimated to be less than 40 ps.

Conclusions:

• RF radiation significantly alters the resistance oscillations in Andreev interferometers, primarily through phase modulation and electron heating.
• The observed π-shift and oscillating resistance dependence on RF amplitude are qualitatively explained by these two processes.
• Further microscopic theoretical investigation is needed to explain unexplained experimental features, such as amplitude/frequency-dependent resistance behavior and transparency windows.