Research Abstract



Transition to a BoseEinstein condensate and relaxation explosion of excitons at sub-Kelvin temperatures

2011年5月31日 Nature Communications 2 : 328 doi: 10.1038/ncomms1335


吉岡 孝高1,3,蔡 恩美2,3* & 五神 真1,3,4

  1. 東京大学大学院理学系研究科物理学専攻
  2. 東京大学大学院工学系研究科物理工学専攻
  3. 独立行政法人 科学技術振興機構
  4. 東京大学大学院工学系研究科附属光量子科学研究センター
Quasiparticles in quantum many-body systems have essential roles in modern physical problems. Bose–Einstein condensation (BEC) of excitons in semiconductors is one of the unobserved quantum statistical phenomena predicted in the photoexcited quasiparticles in many-body electrons. In particular, para-excitons in cuprous oxide have been studied for decades because the decoupling from the radiation field makes the coherent ensemble a purely matter-like wave. However, BEC has turned out to be hard to realize at superfluid liquid helium-4 temperatures due to a two-body inelastic collision process. It is therefore essential to set a lower critical density by further lowering the exciton temperature. Here we cool excitons to sub-Kelvin temperature and spatially confine them to realize the critical number for BEC. We show that BEC manifests itself as a relaxation explosion as has been discussed in atomic hydrogen. The results indicate that dilute excitons are purely bosonic and BEC indeed occurs.