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Frequency dependence of the subharmonic Shapiro steps.
1Theoretical Physics Department 020, Vinča Institute of Nuclear Sciences, University of Belgrade, P. O. Box 522, 11001 Belgrade, Serbia.
Summary
Subharmonic Shapiro steps in a deformable Frenkel-Kontorova model show frequency dependence. Step size oscillates with frequency, influenced by substrate deformation, revealing distinct behavioral patterns.
Area of Science:
- Condensed matter physics
- Nonlinear dynamics
Background:
- Shapiro steps are a hallmark of Josephson junctions and related systems under ac drive.
- The Frenkel-Kontorova model describes systems with discrete translational symmetry, often used to model charge density waves and Josephson ladders.
- Understanding frequency and amplitude dependence of Shapiro steps is crucial for device applications and fundamental physics.
Purpose of the Study:
- To investigate the frequency dependence of subharmonic Shapiro steps in an ac-driven overdamped Frenkel-Kontorova model.
- To analyze the effect of a deformable substrate potential on the appearance and behavior of these steps.
- To classify the different types of oscillatory behavior observed in step size.
Main Methods:
- Simulation of the ac-driven overdamped Frenkel-Kontorova model.
- Analysis of Shapiro step formation and size as a function of driving frequency and amplitude.
- Systematic variation of substrate potential deformation to observe its influence.
Main Results:
- Subharmonic Shapiro steps emerge and increase in number and size with increasing driving frequency when the substrate potential is deformed.
- The size of both harmonic and subharmonic steps exhibits an oscillatory dependence on frequency, particularly in the high-amplitude limit.
- These frequency-dependent oscillations in step size mirror the amplitude dependence and are strongly influenced by substrate deformation, leading to three classified behaviors.
Conclusions:
- Substrate deformability significantly impacts the frequency dependence of Shapiro steps, enabling subharmonic steps and altering their oscillatory behavior.
- The observed oscillatory patterns in step size as a function of frequency provide insights into the nonlinear dynamics of the system.
- Classification of behaviors based on substrate deformation offers a framework for understanding and potentially controlling Shapiro step characteristics.
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