Percolation analysis of a disordered spinor Bose gas

Domain percolation in a quenched ferromagnetic spinor condensate

We show that the easy-axis (EA) magnetic domains formed in a quenched ferromagnetic spinor condensate are described by percolation theory. We introduce a generalized spin rotation to vary the proportion of positive and negative EA domains, allowing us to explore domain percolation. Using simulations we investigate the finite-size scaling behaviour to extract the correlation length critical exponent and the transition point. We analyse the sensitivity of our results to the early-time dynamics of the system, the quadratic Zeeman energy, and the threshold condition used to define the positive (pe…

基于平均场和渗流分析的二维固定填充 $n=1$ 无序玻色-哈伯德模型相图

Phase diagram of disordered Bose-Hubbard model based on mean-field and percolation analysis in two dimensions and at fixed $n=1$ filling

本文基于平均场理论，研究二维无序玻色-哈伯德模型在固定填充下的相图，发现超流相在玻色玻璃相之间重入，并通过渗流分析论证其鲁棒性。

Disordered spinor Bose-Hubbard model

We study the zero temperature phase diagram of the disordered spin-1 Bose-Hubbard model in a 2-dimensional square lattice. To this aim, we use a mean field Gutzwiller ansatz and a probabilistic mean field perturbation theory. The spin interaction induces two different regimes corresponding to a ferromagnetic and antiferromagnetic order. In the ferromagnetic case, the introduction of disorder reproduces analogous features of the disordered scalar Bose-Hubbard model, consisting in the formation of a Bose glass phase between Mott insulator lobes. In the antiferromagnetic regime the phase diagram …

Spin-glass-like behavior in the spin turbulence of spinor Bose-Einstein condensates

We study numerically the spin turbulence in spin-1 ferromagnetic spinor Bose-Einstein condensates (BECs). Spin turbulence (ST) is characterized by a -7/3 power law in the spectrum of the spin-dependent interaction energy. The direction of the spin density vector is spatially disordered but temporally frozen in ST, showing some analogy with the spin glass state. Thus, we introduce the order parameter of spin glass into ST in spinor BECs. When ST develops through some instability, the order parameter grows with a -7/3 power law, thus succeeding in describing ST well.

Different growth rates for spin and superfluid order in a quenched spinor condensate

In this paper we study the coarsening dynamics of a spinor condensate quenched into an easy-axis ferromagnetic phase by a sudden change in the quadratic Zeeman energy. We show that applying a spin rotation prior to changing the Zeeman energy accelerates the development of local order and reduces heating. We examine the longitudinal spin ordering and the superfluid ordering of the system and show that the respective order parameter correlation functions exhibit dynamic scaling in the late time dynamics. Our results also demonstrate that these two types of order grow at different rates, i.e.~wit…

Spin turbulence in spinor Bose-Einstein condensates

We summarize the recent theoretical and numerical works on spin turbulence (ST) in spin-1 spinor Bose-Einstein condensates. When the system is excited from the ground state, it goes through hy- drodynamic instability to ST in which the spin density vector has various disordered direction. The properties of ST depend on whether the spin-dependent interaction is ferromagnetic or antiferro- magnetic. ST has some characteristics different from other kinds of turbulence in quantum fluids. Firstly, the spectrum of the spin-dependent interaction energy exhibits the characteristic power law different …