Abstract
Topological Josephson junctions (JJs), which contain Majorana bound states, are expected to exhibit 4π-periodic current–phase relation, thereby resulting in doubled Shapiro steps under microwave irradiation. We performed numerical calculations of dynamical properties of topological JJs using a modified resistively and capacitively shunted junction model and extensively investigated the progressive evolution of Shapiro steps as a function of the junction parameters and microwave power and frequency. Our calculation results indicate that the suppression of odd-integer Shapiro steps, i.e., evidence of the fractional ac Josephson effect, is enhanced significantly by the increase in the junction capacitance and IcRn product as well as the decrease in the microwave frequency even for the same portion of the 4π-periodic supercurrent. Our study provides the optimal conditions for observing the fractional ac Josephson effect; furthermore, our new model can be used to precisely quantify the topological supercurrent from the experimental data of topological JJs.
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Acknowledgements
We are grateful to Ryundon Kim, Youngmin Cho, Sang-Jun Choi, and H.-S. Sim for the useful discussions. This research was supported by the NRF of Korea through the Basic Science Research Program (2018R1A3B1052827).
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Jang, Y., Doh, YJ. Optimal conditions for observing fractional Josephson effect in topological Josephson junctions. J. Korean Phys. Soc. 78, 58–63 (2021). https://doi.org/10.1007/s40042-020-00035-5
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DOI: https://doi.org/10.1007/s40042-020-00035-5