Details

Autor(en) / Beteiligte

• Utsunomiya, S
• Yamamoto, Y
• Tian, L
• Roumpos, G
• Lai, C. W
• Kumada, N
• Fujisawa, T
• Kuwata-Gonokami, M
• Löffler, A
• Höfling, S
• Forchel, A

Titel

Observation of Bogoliubov excitations in exciton-polariton condensates

Ist Teil von

• Nature physics, 2008-09, Vol.4 (9), p.700-705

Ort / Verlag

London: Nature Publishing Group

Erscheinungsjahr

2008

Link zum Volltext

Quelle

Alma/SFX Local Collection

Beschreibungen/Notizen

• Einstein's 1925 paper predicted the occurrence of Bose-Einstein condensation (BEC) in an ideal gas of non-interacting bosonic particles. However, particle-particle interaction and peculiar excitation spectra are keys for understanding BEC and superfluidity physics. A quantum field-theoretical formulation for a weakly interacting Bose condensed system was developed by Bogoliubov in 1947, which predicted the phonon-like excitation spectrum in the low-momentum regime. The experimental verification of the Bogoliubov theory on the quantitative level was carried out for atomic BEC using the two-photon Bragg scattering technique. Exciton-polaritons in a semiconductor microcavity, which are elementary excitations created by strong coupling between quantum-well excitons and microcavity photons, were proposed as a new BEC candidate in solid-state systems. Recent experiments with exciton-polaritons have demonstrated several interesting signatures from the viewpoint of polariton condensation, such as quantum degeneracy at non-equilibrium conditions, the polariton-bunching effect at the condensation threshold, long spatial coherence and quantum degeneracy at equilibrium conditions. The particle-particle interaction and the Bogoliubov excitation spectrum are at the heart of BEC and superfluidity physics, but have only been studied theoretically for exciton-polaritons. In this letter, we report the first observation of interaction effects on the exciton-polariton condensate and the excitation spectra, which are in quantitative agreement with the Bogoliubov theory.