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Controlled Switching of Bose-Einstein Condensation in a Mixture of Two Species of Polaritons

Hassan Alnatah, Shuang Liang, Qiaochu Wan, Jonathan Beaumariage, Ken West, Kirk Baldwin, Loren N. Pfeiffer, David W. Snoke

TL;DR

This work addresses how two closely populated polariton species compete to condense in a GaAs/AlGaAs microcavity. By temperature-tuning and using angle-resolved photoluminescence, the authors demonstrate condensation switching from the lower to the upper polariton branch as temperature rises, with a metastable, stochastic switching near a critical temperature. A simple two-level model based on Hopfield coefficients and a density-dependent Rabi coupling reproduces the observed phase boundary, linking condensation preference to effective mass and thermal population. The findings reveal non-equilibrium mode competition that enables controllable switching of coherent polariton states, with potential implications for switchable polariton-based photonic devices.

Abstract

We report temperature-dependent switching between lower and upper polariton condensation in a GaAs/AlGaAs microcavity when both of these species have comparable populations in a mixture. Using angle-resolved photoluminescence, we observe that at low temperatures, condensation occurs in the lower polariton branch, while at elevated temperatures, the upper polariton branch can become favored. At an intermediate temperature, we observe instability in the condensate formation, characterized by metastable correlations of the fluctuations in intensity and linewidth of the lower and upper polariton branches.

Controlled Switching of Bose-Einstein Condensation in a Mixture of Two Species of Polaritons

TL;DR

This work addresses how two closely populated polariton species compete to condense in a GaAs/AlGaAs microcavity. By temperature-tuning and using angle-resolved photoluminescence, the authors demonstrate condensation switching from the lower to the upper polariton branch as temperature rises, with a metastable, stochastic switching near a critical temperature. A simple two-level model based on Hopfield coefficients and a density-dependent Rabi coupling reproduces the observed phase boundary, linking condensation preference to effective mass and thermal population. The findings reveal non-equilibrium mode competition that enables controllable switching of coherent polariton states, with potential implications for switchable polariton-based photonic devices.

Abstract

We report temperature-dependent switching between lower and upper polariton condensation in a GaAs/AlGaAs microcavity when both of these species have comparable populations in a mixture. Using angle-resolved photoluminescence, we observe that at low temperatures, condensation occurs in the lower polariton branch, while at elevated temperatures, the upper polariton branch can become favored. At an intermediate temperature, we observe instability in the condensate formation, characterized by metastable correlations of the fluctuations in intensity and linewidth of the lower and upper polariton branches.
Paper Structure (6 sections, 6 equations, 5 figures)

This paper contains 6 sections, 6 equations, 5 figures.

Table of Contents

  1. INTRODUCTION
  2. EXPERIMENTAL METHODS
  3. EXPERIMENTAL RESULTS
  4. DISCUSSION
  5. CONCLUSIONS
  6. Acknowledgments

Figures (5)

  • Figure 1: Energy-resolved PL at 100 K and 70 K.(a) angle-resolved PL measurements of the polariton at very low pumping power with a LP exciton fraction of 0.51 and (b) high pumping power at 100 K. (c,d) angle-resolved PL measurements at 70 K and LP exciton fraction 0.22 under low (c) and high (d) pumping conditions.
  • Figure 2: Anticorrelated coherence at a fixed power and temperature (80 K), for LP exciton fraction of 0.68, near the condensation threshold. (a) The energy, (b) the linewidth and (c) the maximum intensity as a function on snapshot number.
  • Figure 3: Selected snapshots at fixed temperature of 80 K, for LP exciton fraction of 0.68 and pump power corresponding to Fig. \ref{['fig:switching_dynamics']}, for identical experimental conditions. (a) The LP is brighter, (b) the LP and UP have the same brightness, (c) the UP is brighter. The exciton fraction of the LP is 0.68.
  • Figure 4: Characteristics of the PL lines at 80 K, averaged over many shots as in the data of Figure \ref{['fig:switching_dynamics']}. (a) The intensity at $k=0$ of the polaritons as a function of pump power. (b) The energies of the polariton lines at $k=0$ as a function of the pump power. (c) Full width at half maximum at $k=0$.
  • Figure 5: Phase diagram showing the LP exciton fraction versus temperature for LP and UP condensates. The exciton fraction for various locations on the microcavity sample has been deduced using fits to the energies $E_{LP}(\theta)$ and $E_{UP}(\theta)$ from data like that shown in Figure \ref{['fig:EvsK_condensation']} at low pump density, using a model like that of Eq. (\ref{['matrix']}) but with three levels for the photon, heavy-hole exciton and light-hole exciton in GaAs quantum wells. Triangles represent conditions where condensation occurs in the upper polariton branch, while circles represent condensation in the lower polariton branch. The color bar gives the emission energy of the condensate relative to the zero-density upper polariton branch. The symbol with the square gives the conditions of the metastable jumping between the different states seen in Figures 2 and 3. The solid black line is given by Eq. \ref{['eq:phase_diagram_theory']} for the parameters given in the text.