Magnetic fluctuations and self-energy effects in two-dimensional itinerant systems with a van Hove singularity in the electronic spectrum
Magnetic fluctuations and self-energy effects in two-dimensional itinerant systems with a van Hove singularity in the electronic spectrum
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电子谱中具有范霍夫奇点的二维流动系统中的磁涨落和自能效应
DOI：
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发表时间：
2010
期刊：
影响因子：
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通讯作者：
A. Katanin
中科院分区：
文献类型：
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作者：
P. A. Igoshev;V. Irkhin;A. Katanin
利用泛函重整化群方法，以温度为尺度参数，研究了二维费米子系统中铁磁有序和无公度有序的竞争。我们假设费米面（FS）基本上是弯曲的，位于货车霍韦奇点附近，并考虑了自能修正。结果表明，相对于货车霍韦奇点（VHS），磁涨落的性质与费米能级位置是强不对称的。对于费米能级以上的VHS，我们发现在低温下占主导地位的不相称的磁波动，而低于VHS水平，我们发现铁磁基态的迹象。与Mermin-Wagner定理一致，在有限温度和小磁场下，我们获得了相当小的磁化强度，它似乎是磁场的幂律函数。研究发现，FS曲率略有增加的相关效应，并在足够低的温度下的重整化带宽减小。
We investigate a competition of tendencies towards ferromagnetic and incommensurate order in two-dimensional fermionic systems within functional renormalization group technique using temperature as a scale parameter. We assume that the Fermi surface (FS) is substantially curved, lies in the vicinity of van Hove singularity points and perform an account of the self-energy corrections. It is shown that the character of magnetic fluctuations is strongly asymmetric with respect to the Fermi level position relatively to van Hove singularity (VHS). For the Fermi level above VHS we find at low temperatures dominant incommensurate magnetic fluctuations, while below VHS level we find indications for ferromagnetic ground state. In agreement with the Mermin-Wagner theorem, at finite temperatures and in small magnetic fields we obtain rather small magnetization, which appears to be a power-law function of magnetic field. It is found that the FS curvature is slightly increased by correlation effects, and the renormalized bandwidth decreases at sufficiently low temperatures.