Achieving µeV resolution in scanning tunneling spectroscopy at mK temperatures in Al-Al SIS junctions

ORAL

Abstract

Improved energy resolution in spectroscopic measurements is one of the main motivations for conducting Scanning Probe Microscopy (SPM) experiments at temperatures of tens of mK using a dilution refrigerator (DR). However, SPM instruments at these temperatures have not always achieved an energy resolution consistent with the DR temperature due to electrical noise coupling into the tunnel junction. Here, we present Scanning tunneling spectroscopy measurements of an Al-Al Josephson junction using an Al thin film grown in situ, together with an Al probe tip. The improved performance is achieved by optimizing our SPM operating in ultra-high vacuum (UHV) inside a DR with a base temperature of 10mK and magnetic field up to 15T [1]. Home built Radio Frequency (RF) powder filters located at the mixing chamber shield the tunnel junction from room temperature RF noise. Further RF filtering at the UHV chamber room temperature feedthroughs, together with attention to grounding, lead to an order of magnitude improved resolution over previous measurements. We demonstrate an energy resolution in the low ueV range and discuss the trials and tribulations to achieve this resolution and the causes of the residual intrinsic energy broadening that is observed.

[1] Song et al., RSI 81, 121101 (2010)

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Presenters

  • Johannes Schwenk

    National Institute of Standards and Technology, Physical Measurement Laboratory, National Institute of Standards and Technology

Authors

  • Johannes Schwenk

    National Institute of Standards and Technology, Physical Measurement Laboratory, National Institute of Standards and Technology

  • Sungmin Kim

    National Institute of Standards and Technology, Physical Measurement Laboratory, National Institute of Standards and Technology

  • Julian Berwanger

    Institut für Experimentelle und Angewandte Physik, Universität Regensburg

  • William G Cullen

    National Institute of Standards and Technology, Physical Measurement Laboratory, National Institute of Standards and Technology

  • Steven R Blankenship

    National Institute of Standards and Technology

  • Young Kuk

    Center for Quantum Nanoscience, Ewha Womans University, Seoul, Korea, Center for Quantum Nanoscience, Institute of Basic Science, Ewha Womans University, Seoul, Korea, Seoul National University, Department of Physics and Astronomy, Seoul National University

  • Franz J Giessibl

    Institut für Experimentelle und Angewandte Physik, Universität Regensburg

  • Joseph A Stroscio

    National Institute of Standards and Technology, Physical Measurement Laboratory, National Institute of Standards and Technology, National Institute of Standards and Technology (NIST)