CPM Seminar

Exploring interactions and coherent transport
with transport and tunneling in 1D systems

Mike Lilly

Sandia National Labs

The observation of quantized conductance steps in ballistic semiconductor quantum wires is an early example of the now very broad field of nanoelectronics. Although the physics of plateaus at quantized values of G₀ = 2e²/h is easily understood using non-interacting quantum mechanics, Coulomb interactions are expected to play a key role in 1D systems. In this talk, transport experiments on single and double quantum wires will be presented. In the first part, the interplay between disorder and interactions in long single wires and wires with a variable density will be tested with a variety of conductance measurements. The second part of the talk focuses on tunneling in a system of vertically coupled quantum wires. These nanostructures are fabricated from bilayer electron samples with electron beam lithography on both top and bottom defining the double wire. Parallel conductance as a function of split gate voltages provide a map of the 1D subband occupations; tunneling measurements can be made with any combination of subbands occupied in each wire. The full tunneling spectroscopy is measured using both a voltage between the wires and a parallel magnetic field to learn about both the energy and momentum dependence of tunneling events. We compare the data to a non-interacting model of tunneling. Deviations from the simple picture may require analysis of the 1D systems as Luttinger liquids. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy under contract DE-AC04-94AL85000.