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arXiv 0808.2124cond-mat.stat-mechcond-mat.supr-con
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Blume-Emery-Griffiths模型扩展的Monte Carlo研究

Monte Carlo studies of extensions of the Blume-Emery-Griffiths model

C. C. Loois, G. T. Barkema, C. Morais Smith

摘要:

为了研究具有两个序参量的二维系统,如磁超导体或两组分玻色-爱因斯坦凝聚体,我们将Blume-Emery-Griffiths(BEG)模型推广到两组分BEG模型.使用蒙特卡罗模拟的模型进行了研究,并确定在存在和不存在外部磁场的温度-浓度相图。该模型展示了丰富的相图,包括向超导性和磁性共存的相的二级转变。结果进行了比较与实验铈基重费米子超导体。为了研究冷原子混合物,我们还模拟了带囚禁势的BEG模型和双组分BEG模型。在带陷阱的BEG模型中,不再有一级相变到真正的相分离区,而是有一个过渡到一种相分离区。与不平衡费米混合物的关系进行了讨论。本文给出了带势阱的二分量BEG模型的相图,该模型可以描述玻色子-玻色子混合冷原子。虽然后者还没有实验结果,但我们希望我们的预测可以帮助刺激未来的实验。

英文摘要:

We extend the Blume-Emery-Griffiths (BEG) model to a two-component BEG model in order to study 2D systems with two order parameters, such as magnetic superconductors or two-component Bose-Einstein condensates. The model is investigated using Monte Carlo simulations, and the temperature-concentration phase diagram is determined in the presence and absence of an external magnetic field. This model exhibits a rich phase diagram, including a second-order transition to a phase where superconductivity and magnetism coexist. Results are compared with experiments on Cerium-based heavy-fermion superconductors. To study cold atom mixtures, we also simulate the BEG and two-component BEG models with a trapping potential. In the BEG model with a trap, there is no longer a first order transition to a true phase-separated regime, but a crossover to a kind of phase-separated region. The relation with imbalanced fermi-mixtures is discussed. We present the phase diagram of the two-component BEG model with a trap, which can describe boson-boson mixtures of cold atoms. Although there are no experimental results yet for the latter, we hope that our predictions could help to stimulate future experiments in this direction.

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