# 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*