Low-temperature thermodynamics for a flat-band ferromagnet: Rigorous versus numerical results
Low-temperature thermodynamics for a flat-band ferromagnet: Rigorous versus numerical results
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DOI：
10.1103/physrevb.76.220402
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发表时间：
2007-03
影响因子：
3.7
通讯作者：
O. Derzhko;A. Honecker;J. Richter
中科院分区：
文献类型：
--
作者：
O. Derzhko;A. Honecker;J. Richter
锯齿链上的排斥性Hubbard模型显示出最低的单电子带，对于特定的跳变参数选择，该带是完全无色散的（平坦的）。我们构造了精确的多电子基态，使电子填充达到1/4。我们将电子模型的低能量自由度映射到链上的经典硬二聚体模型，从而获得基态简并以及围绕特定化学势值的低温热力学量的封闭形式表达式。我们将分析结果与互补的数值数据进行比较。虽然我们考虑的是一个特定的模型，但我们相信我们的一些结果，如比热中的低温峰，对于平带铁磁体是通用的。
The repulsive Hubbard model on a sawtooth chain exhibits the lowest single-electron band which is completely dispersionless (flat) for a specific choice of the hopping parameters. We construct exact many-electron ground states for electron fillings up to 1/4. We map the low-energy degrees of freedom of the electron model to a model of classical hard dimers on a chain and, as a result, obtain the ground-state degeneracy as well as closed-form expressions for the low-temperature thermodynamic quantities around a particular value of the chemical potential. We compare our analytical findings with complementary numerical data. Although we consider a specific model, we believe that some of our results such as a low-temperature peak in the specific heat are generic for flat-band ferromagnets.