Regensburg 2013 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 71: Exciton polaritons and their condensates (HL, jointly with TT)

HL 71.2: Talk

Thursday, March 14, 2013, 09:45–10:00, H2

Weak periodic modulation of exciton-polariton condensates — •Edgar Cerda-Mendez¹, Dipankar Sarkar², Klaus Biermann¹, Dmitry Krizhanovski², Maurice Skolnick², and Paulo Santos¹ — ¹Paul Drude Institut for Solid State Physics, Berlin, Germany — ²Department of Physics and Astronomy, University of Sheffield, Sheffield, United Kingdom

Macroscopic quantum behavior manifest when bosonic particles undergo a phase transition to a condensate state described by a single quantum wavefunction. Such behavior also occurs in microcavities containing quantum wells (QWs), where quasiparticles called polaritons arise from the strong coupling of photons and the QW excitons. In this work, we study the properties of polariton condensates in a shallow square lattice created via acoustic modulation. We demonstrate the formation of an extended state with negative effective mass at the corners (i.e. M-points) of the square lattice mini-Brillouin Zone. Also, optical threshold intensities for condensation are reduced, which is attributed to the lower density of states at the M-points and to the negative effective mass which compensates polariton drift induced by repulsive interactions. Both effects may allow to reach the critical density for condensation more efficiently than at the center of the MBZ (i.e. the Γ point). Finally, the momentum spread of the M-point states is independent from the area covered by the MCP, showing that the wavefunction of the MCP has a self-induced intrinsic coherence length. This work opens the way for investigation of polariton quantum phases such as a Bose Glass, Mott insulator or bright gap solitons.