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PRODID:UW-Madison-Physics-Events
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UID:UW-Physics-Event-9048
DTSTART:20250108T190000Z
DTEND:20250108T210000Z
DTSTAMP:20260413T171620Z
LAST-MODIFIED:20250103T230752Z
LOCATION:5310 Chamberlin
SUMMARY:Developing Josephson Junction Microwave Spectroscopy as a Moda
 lity Compatible with Scanned Probe Microscopy at LHe Temperatures\, Th
 esis Defense\, Margaret Fortman\, Physics PhD Graduate Student
DESCRIPTION:Developing new diagnostic tools to understand superconduct
 ing surface impurities is crucial for the future of quantum supercondu
 cting circuity as well as probing new emergent states in condensed mat
 ter. Josephson junction spectroscopy (JJS) in a scanned geometry offer
 s a way to probe defects in superconductors directly\, while also corr
 elating their electronic and spatial properties. In this work we show 
 advances towards implementing JJS in a scanning tunneling microscope (
 STM)\, where the Josephson junction is created between the superconduc
 ting tip and superconducting sample. We first present a way to perform
  this measurement in an STM by creating a new type of tip that leverag
 es the HF filtering properties of a large tip-sample capacitance desig
 n. To demonstrate the benefit of this approach\, we then show how a la
 rge cross junction capacitance improves performance at elevated temper
 atures using fabricated Nb-based Josephson junction devices. We also d
 iscuss the development of iron selenide as a promising superconducting
  surface on which to implement this technique. Lastly\, we present pro
 mising results of our high capacitance STM tip showing its ability to 
 decrease thermal noise and P(E)-broadening and discuss future possibil
 ities of this tool.
URL:https://www.physics.wisc.edu/events/?id=9048
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