Diessel Oriana K, Diehl Sebastian, Chiocchetta Alessio
Max-Planck-Institute of Quantum Optics, Hans-Kopfermann-Strasse 1, 85748 Garching, Germany.
Institute for Theoretical Physics, University of Cologne, Zülpicher Strasse 77, 50937 Cologne, Germany.
Phys Rev Lett. 2022 Feb 18;128(7):070401. doi: 10.1103/PhysRevLett.128.070401.
In bosonic gases at thermal equilibrium, an external quadratic drive can induce a Bose-Einstein condensation described by the Ising transition, as a consequence of the explicitly broken U(1) phase rotation symmetry down to Z_{2}. However, in physical realizations such as exciton polaritons and nonlinear photonic lattices, thermal equilibrium is lost and the state is rather determined by a balance between losses and external drive. A fundamental question is then how nonequilibrium fluctuations affect this transition. Here, we show that in a two-dimensional driven-dissipative Bose system the Ising phase is suppressed and replaced by a nonequilibrium phase featuring Kardar-Parisi-Zhang (KPZ) physics. Its emergence is rooted in a U(1)-symmetry restoration mechanism enabled by the strong fluctuations in reduced dimensionality. Moreover, we show that the presence of the quadratic drive term enhances the visibility of the KPZ scaling, compared to two-dimensional U(1)-symmetric gases, where it has remained so far elusive.
在处于热平衡的玻色气体中,外部二次驱动可诱导出由伊辛转变描述的玻色 - 爱因斯坦凝聚,这是由于明确打破的U(1)相位旋转对称性降至Z₂的结果。然而,在诸如激子极化激元和非线性光子晶格等物理实现中,热平衡丧失,状态反而由损耗与外部驱动之间的平衡决定。于是一个基本问题是,非平衡涨落如何影响这种转变。在此,我们表明,在二维驱动耗散玻色系统中,伊辛相受到抑制,并被具有 Kardar-Parisi-Zhang(KPZ)物理特性的非平衡相所取代。它的出现源于由降维中的强涨落促成的U(1)对称性恢复机制。此外,我们表明,与二维U(1)对称气体相比,二次驱动项的存在增强了KPZ标度的可见性,而在二维U(1)对称气体中,KPZ标度迄今一直难以捉摸。