论文标题
巡回FCC晶格电子系统具有高阶范霍夫奇异性的铁磁不稳定性：功能重新归一化组研究
Ferromagnetic instability in itinerant fcc lattice electron systems with higher order van Hove singularities: Functional renormalization group study
论文作者
论文摘要
我们研究了使用温度作为比例参数，在功能重新归一化组中以面部为中心的立方晶格中的非脱位哈伯德模型中的铁磁有序的可能性。我们假设最接近的，下一个最新的和下一个临时的跳跃参数，提供了更高阶（巨型）范·霍夫（Van Hove）的奇异性。一环近似中始终描述了具有降低温度的铁磁不稳定性的形成。计算化学势与温度相图。我们发现铁磁顺序仅是为了足够强烈的状态密度和填充物的足够强大的差异。获得的居里温度比随机相近似的结果小的数量级。抑制铁磁性的主要起源是筛选粒子粒子通道中的相互作用。当费米水平从van霍夫奇点移开时，我们也没有发现明显的不符合顺序序列的趋势，因此获得了从铁磁相到顺磁相的一阶量子相变。
We investigate the possibility of ferromagnetic ordering in the non-degenerate Hubbard model on the face-centered cubic lattice within the functional renormalization group technique using temperature as a scale parameter. We assume the relations between nearest, next-nearest, and next-next-nearest hopping parameters providing higher order (giant) van Hove singularity of the density of states. The ferromagnetic instability formation with lowering temperature is described consistently in the one-loop approximation for a one-particle irreducible vertex of two-particle electron interaction. The chemical potential versus temperature phase diagrams are calculated. We find ferromagnetic order only for sufficiently strong divergence of the density of states and fillings in the vicinity of van Hove singularity. The obtained Curie temperature is more than an order of magnitude smaller than the results of the random-phase approximation. The main origin of the suppression of ferromagnetism is the screening of interaction in the particle-particle channel. We also do not find the pronounced tendency towards incommensurate order when the Fermi level is moved away from a van Hove singularity, such that the first order quantum phase transitions from the ferro- to paramagnetic phase are obtained.
