Fermi-edge singularities in linear and nonlinear ultrafast spectroscopy - art. no. 245321

We discuss Fermi-edge singularity effects on the linear and nonlinear trans ient response of an electron gas in a doped semiconductor. We use a bosoniz ation scheme to describe the low-energy excitations, which allows us to com pute the time and temperature dependence of the response functions. Coheren t control of the energy absorption at resonance is analyzed in the linear r egime. It is shown that a phase shift appears in the coherent control oscil lations, which is not present in the excitonic case. The nonlinear response is calculated analytically and used to predict that four wave-mixing exper iments would present a Fermi-edge singularity when the exciting energy is v aried. A new dephasing mechanism is predicted in doped samples that depends linearly on temperature and is produced by the low-energy bosonic excitati ons in the conduction band.