Scanning Tunneling Spectroscopy Studies of Organic Superconductors

点击翻译按钮获取中文摘要

*** NON-TECHNICAL ABSTRACT ***The Bechgaard salts are one-dimensional organic conductors which display most of the electronic phases known in condensed matter physics. This project will use a scanning tunneling microscope (STM) to study one such material, (TMTSF)2ClO4, which superconducts at temperatures below 1.5 K. Ordinarily, superconductivity is destroyed by a high magnetic field, but in this case superconductivity may be preserved up to arbitrarily high fields by two unusual yet unproven effects: triplet pairing, and field-induced one-dimensionality. Triplet superconductivity has also been proposed as a route to quantum computing. This award will fund construction of an ultra-stable STM on a helium fridge, with temperature control down to 250 mK, low temperature cleaver to expose clean surfaces, simultaneous transport measurement capabilities, and a triple-axis magnetic field. Specific energy features in the atomically resolved STM images may provide the smoking gun signature for triplet superconductivity. The broader impact of this project will include training of undergraduate and graduate students, and a website dedicated to clarifying organic superconductors for non-experts and tabulating their quantifiable properties for experts.***TECHNICAL ABSTRACT ***This individual investigator award will fund a scanning tunneling microscopy (STM) study of the Bechgaard salt (TMTSF)2ClO4, a quasi-one-dimensional organic superconductor with Tc = 1.5 K. A unique confluence of triplet superconductivity and field-induced dimensional crossover may render the upper critical field Hc2 essentially infinite along one crystal axis, however triplet superconductivity remains unproven. The PI will build an ultra-stable STM on a 3He fridge, with variable temperature control, low temperature cleaver to expose clean surfaces, simultaneous transport measurement capabilities, and triple-axis magnetic field. This experiment will use clean vacuum tunnel junctions, verified with atomic resolution, to probe for the Andreev bound state signature of triplet superconductivity. The project will also attempt to grow (TMTSF)2ClO4 with magnetic or non-magnetic impurities, and to study their local effects, in light of the single-triplet debate. The broader impact of this project will include training of undergraduate and graduate students, and a website dedicated to clarifying organic superconductors for non-experts and tabulating their quantifiable properties for experts.