Condensed Matter Seminar Series

Fermi – edge singularity at tunneling in low dimensional semiconductors structures

Ivan Larkin

International Center of Condensed Matter Physics,  Brasília DF, Brazil

Thursday, November 12,  11:00 am,  Room 298,  Physics Building

The Fermi-edge singularity (FES) is a many-body interaction effect, which has been first observed in X-ray absorption in metals.  Theoretical work by K. Matveev and A. Larkin predicted the existence of an FES effect in I-V curves of tunneling devices for the case when electrons tunnel through a localized state in a potential barrier. This effect has been observed later in the current-voltage characteristics of several semiconductor heterostructure devices in a broad range of magnetic fields. Our calculations show that FES exponent  is very sensitive to the device geometry and spectrum of the Fermi electrons. We have calculated critical exponent of the Fermi edge singularity in tunneling current as a function of magnetic field B and parameters of the heterostructure.  We have used lowest Landau level approximation for electrons in emitter and performed calculation of scattering matrix in Born approximation. Physically, the effect of the rapidly increasing FES exponent arises from the effective localization of the emitter electrons in magnetic parabola.  Fermi electrons at the lowest Landau level efficiently interact with the Quantum Dot Coulomb potential that causes an enhancement of the scattering phase. We analyzed carefully effect anisotropy in magnetotunneling and have revealed strong anisotropy of tunneling matrix element and weak anisotropy of FES exponent.

Host: Gleb Finkelstein

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