Can we play bowling with electrons?

November 11, 2016

Jongsoo Yoon, Department of Physics, University of Virginia

 Much of the electronic properties of metals can be understood in the framework of the independent or free electron model, where the electron-electron interaction is ignored. In such a model electrons move freely within the metal, much like bowling balls rolling in a lane. Conventional theories expect that the ground state of the electron systems in two dimensions should be localized, or an electrically insulating state; in bowling analogy, the bowling balls rolled in a lane should never reach the pins.

Experiments, however, have shown a strong indication that the ground state is actually conducting. Although the mechanism behind the unexpected conducting ground state is still mysterious, the electron-electron interaction is believed to hold the key to the mechanism. Interestingly, unexpected conducting ground states with very similar characteristics are observed in systems where the electron-electron interaction is repulsive (electrons confined in the semiconductor interface) as well as the interaction is attractive (superconducting ultra-thin films where the superconductivity is suppressed).

In this talk, we concentrate on the experimental results of the mysterious conducting state observed on ultra-thin superconducting tantalum films. We will identify non-trivial electronic transport properties that are intrinsic to the mysterious conducting state, and map the three-dimensional phase diagram in magnetic field-temperature-disorder space.