Abstract
As scanning tunneling microscopy is pushed towards fast local dynamics, a quantitative understanding of tunnel junctions under the influence of a fast AC driving signal is required, especially at the ultra-low temperatures relevant to spin dynamics and correlated electron states. We subject a superconductor-insulator-superconductor junction to a microwave signal from an antenna mounted \textit{in situ} and examine the DC response of the contact to this driving signal. Quasi-particle tunneling and the Josephson effect can be interpreted in the framework of Tien-Gordon theory. The situation is more complex when it comes to higher order effects such as multiple Andreev reflections. Microwave assisted tunneling unravel these complex processes, providing deeper insights into tunneling than are available in a pure DC measurement.
Highlights
With its combination of supreme spatial resolution and spectroscopic imaging, the scanning tunneling microscope (STM) is a workhorse of mesoscopic and nanoscale physics [1]
As scanning tunneling microscopy is pushed towards fast local dynamics, a quantitative understanding of tunnel junctions under the influence of a fast ac driving signal is required, especially at the ultralow temperatures relevant to spin dynamics and correlated electron states
We study SIS tunneling between a V(100) surface and a vanadium tip in a commercial STM system (Unisoku USM1300) operating at 300 mK base temperature and fitted with a custom-built antenna assembly capable of delivering a microwave signal between 60–90 GHz to the junction, see Fig. 1(a)
Summary
With its combination of supreme spatial resolution and spectroscopic imaging, the scanning tunneling microscope (STM) is a workhorse of mesoscopic and nanoscale physics [1]. More advanced theories suggest that SIS tunneling under microwave irradiation must be understood through MARs while accounting for microwave interactions at every step of these higher-order processes [19] In this MAR model, the microwave signal is modeled as a time-dependent phase difference between tip and sample electrodes and MARs arise naturally through higher-order terms. We report measurements of quasiparticle, Cooper pair, and MAR tunneling in an SIS junction under microwave irradiation These experimental findings are compared with predictions from the Tien-Gordon and the microwave-assisted MAR models, respectively. The latter one is found to be capable of correctly modeling the impact of microwave driving on the charge transfer process. GN ≈ 8.4 × 10−3 G0 for all spectra
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
