Two-dimensional Fourier-transform Spectra Research Articles

Two-Quantum Many-Body Coherences in Two-Dimensional Fourier-Transform Spectra of Exciton Resonances in Semiconductor Quantum Wells

We present experimental coherent two-dimensional Fourier-transform spectra of Wannier exciton resonances in semiconductor quantum wells generated by a pulse sequence that isolates two-quantum coherences. By measuring the real part of the signals, we determine that the spectra are dominated by two-quantum coherences due to mean-field many-body interactions, rather than bound biexcitons. Simulations performed using dynamics controlled truncation agree with the experiments.

Modeling excitonic line shapes in weakly disordered semiconductor nanostructures

Excitonic spectra of weakly disordered semiconductor heterostructures are simulated on the basis of a one-dimensional tight-binding model. The influence of the length scale of weak disorder in quantum wells on the redshift of the excitonic peak and its linewidth is studied. By calculating two-dimensional Fourier-transform spectra we are able to determine the contribution of disorder to inhomogeneous and also to homogeneous broadenings separately. This disorder-induced dephasing is related to a Fano-type coupling and leads to contributions to the homogeneous linewidth that depends on energy within the inhomogeneously broadened line. The model includes heavy- and light-hole excitons and yields smaller inhomogeneous broadening for the light-hole exciton if compared to the heavy-hole exciton, which agrees qualitatively with the experiment.

Polarization dependence of semiconductor exciton and biexciton contributions to phase-resolved optical two-dimensional Fourier-transform spectra

We study the coherent light-matter interactions associated with excitons, biexcitons, and many-body effects in GaAs quantum wells. For most polarization configurations the phase-resolved two-dimensional Fourier-transform (2DFT) spectra are dominated by excitonic features, where their strength and dispersive line shapes are due to many-body interactions. Cross-linear excitation suppresses many-body interactions, changing the line shape and strength of the 2DFT features.

Determination of homogeneous and inhomogeneous broadening in semiconductor nanostructures by two-dimensional Fourier-transform optical spectroscopy

The imaginary part of two-dimensional Fourier-transform spectra in the rephasing and nonrephasing modes is used to analyze the homogeneous and inhomogeneous broadening of excitonic resonances in semiconductor nanostructures. Microscopic calculations that include heavy- and light-hole excitons as well as coherent biexcitonic many-body correlations reveal distinct differences between the rephasing and nonrephasing spectra. A procedure is proposed that allows separation of disorder-induced broadening in complex systems that show several coupled resonances.

Signatures of many-particle correlations in two-dimensional Fourier-transform spectra of semiconductor nanostructures

On the basis of a microscopic theory, the signatures of many-particle correlations in Two-Dimensional Fourier-Transform Spectra (2D-FTS) of semiconductor nanostructures are identified and compared to experimental data. Spectra in the photon energy range of the heavy-hole and light-hole excitonic resonances show characteristic features due to correlations, which depend on the relative polarization directions of the excitation pulses.