Thermal averages in a quantum point contact with a single coherent wave packet

E. J. Heller, K. E. Aidala, B. J. Leroy, A. C. Bleszynski, A. Kalben, R. M. Westervelt, K. D. Maranowski, A. C. Gossard

Research output: Contribution to journalArticlepeer-review

22 Scopus citations


A novel formal equivalence between thermal averages of coherent properties (e.g., conductance) and time averages of a single wave packet arises for Fermi gases and certain geometries. In the case of one open channel in a quantum point contact (QPC), only one wave packet history, with the wave packet width equal to the thermal length, completely determines the thermally averaged conductance. The formal equivalence moreover allows very simple physical interpretations of interference features surviving under thermal averaging. Simply put, pieces of the thermal wave packet returning to the QPC along independent paths must arrive at the same time in order to interfere. Remarkably, one immediate result of this approach is that higher temperature leads to narrower wave packets and therefore better resolution of events in the time domain. In effect, experiments at 4.2 K are performing time-gated experiments at better than a gigahertz. Experiments involving thermally averaged ballistic conductance in 2DEGS are presented as an application of this picture.

Original languageEnglish (US)
Pages (from-to)1285-1292
Number of pages8
JournalNano Letters
Issue number7
StatePublished - Jul 2005

ASJC Scopus subject areas

  • Bioengineering
  • General Chemistry
  • General Materials Science
  • Condensed Matter Physics
  • Mechanical Engineering


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