Electrical Tuning of Nonlinearities in Exciton-Polariton Condensates

A primary limitation of the intensively researched polaritonic systems compared to their atomic counterparts for the study of strongly correlated phenomena and many-body physics is their relatively weak two-particle interactions compared to disorder. Here, we show how new opportunities to enhance such on-site interactions and nonlinearities arise by tuning the exciton-polariton dipole moment in electrically biased semiconductor microcavities incorporating wide quantum wells. The applied field results in a twofold enhancement of exciton-exciton interactions as well as more efficiently driving relaxation towards low energy polariton states, thus, reducing condensation threshold.

Figure 1

(a) Schematic illustration of the electrically gated wide QW MC. (b) Schematic representation of electron and hole wave functions in a wide QW under the presence of electric field and the corresponding charge distribution.

Figure 2

Theoretical calculations as a function of the electric field for (a) the radiative lifetime and dipole moment for the HH excitons, (b) HH exciton interaction strength. The three purple square points are experimental data exported as discussed in the text.

Figure 3

Time-resolved PL at four discrete electric field values for (a) below laser threshold ($P=0.2\mathrm{mW}$) and (b) above laser threshold ($P=4.25\mathrm{mW}$). The inset of (b) is a schematic illustration of the various relaxation mechanisms incorporated in the rate equations.

Figure 4

(a) Logarithmic power dependent PL spectra at zero (black) and $12.5\mathrm{kV}/\mathrm{cm}$ (red) electric fields. (b) The polariton energy blueshift at three different electric field values. (c) Integrated PL emission extracted from the corresponding spectra of (a). Reduction of polariton laser threshold versus electric field appears in the inset. The squares are experimental data while the solid line is obtained from theoretical calculations.