Fractional Quantum Hall Effect in Silicon

The observation of the fractional quantum Hall effect (FQHE) is the sine qua non of high quality two dimensional (2D) materials and surfaces. Originally observed thirty years ago, the FQHE is a delicate correlated state of 2D electrons that is easily destroyed by any randomness or disorder in the potential experienced by the electrons.  The invention of modulation doping and the perfection of molecular beam epitaxy (MBE) in GaAs were key to the discovery of the FQHE, and use of these techniques has been necessary for the development of most of the other materials where the FQHE has been observed.  The recent observation of the FQHE in graphene however, has proven that very clean surfaces—not necessarily prepared in an MBE chamber—are also excellent systems in which to probe the physics of 2D electrons.

Almost a decade’s work by our group in perfecting hydrogen terminated silicon surface devices has culminated in devices with mobilities (the parameter that quantifies the perfection of a system of charge carriers on a 2D surface) comparable to those where the FQHE is routinely observed.  Our data show an extended hierarchy of FQHE states surrounding filling factor n=3/2.  Interestingly, only fractions with even numerator are visible in this region, an indication that the silicon valley degeneracy is preserved in the FQHE regime.  FQHE states in a valley degeneate system such as silicon may be a favorable environment for topological qubits for quantum information processing.

Team Members