Optomechanical response of a strongly interacting Fermi gas

強く相互作用するフェルミ気体のオプトメカニカル応答

Helson, V.*; Zwettler, T.*; Roux, K.*; 小西 秀樹*; 内野 瞬   ; Brantut, J.-P.*

Helson, V.*; Zwettler, T.*; Roux, K.*; Konishi, Hideki*; Uchino, Shun; Brantut, J.-P.*

光共振器と結合した強く相互作用するフェルミ気体に関する理論的・実験的解析を行った。我々は、この系における光双安定性現象を確認し、その応答が原子間相互作用を変化させることで大きく変更を受けることを明らかにした。また、観測結果は、演算子積展開に基づく理論解析と良い一致を示すことがわかった。

We study a Fermi gas with strong, tunable interactions dispersively coupled to a high-finesse cavity. Upon probing the system along the cavity axis, we observe a strong optomechanical Kerr nonlinearity originating from the density response of the gas to the intracavity field. Measuring the non-linearity as a function of interaction strength, we extract the zero-frequency density response function of the Fermi gas, and find an increase by a factor of two from the Bardeen-Cooper-Schrieffer to the Bose-Einstein condensate regime. The results are in quantitative agreement with a theory based on operator-product expansion, expressing the density response in terms of universal functions of the interactions, the contact and the internal energy of the gas.