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arXiv 0711.0952cond-mat.str-elcond-mat.mtrl-scicond-mat.supr-conmath-phmath.MP
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关于相互作用费米子系统基态粒子数的Luttinger定理

On the Luttinger theorem concerning number of particles in the ground states of systems of interacting fermions

Behnam Farid

摘要:

分析了Luttinger和Ward对Luttinger定理的原始证明,根据该定理,对于均匀的(相互作用)费米子系统的基态,可以是金属的或绝缘的,对应于Gs(k;mu)的非负值的k点的数目等于这些基态中自旋指数为s的粒子的总数。这里G_s(k;mu)是自旋指数为s的粒子在化学势μ处的单粒子格林函数。对于两体相互作用势是短程的情况,特别是对于晶格模型,我们明确地证明了这个定理是无条件有效的,不管裸相互作用势的强度如何。我们得出这一结论,除其他事项外,表明微扰级数展开的自能的骨架图,遇到的证明Luttinger-沃德恒等式,是一致收敛的几乎所有的动量和能量。我们进一步调查的机制,失败的Luttinger定理的一些报告的情况下。除了一个例外,在本文中考虑的所有情况下,我们表明,明显的失败的Luttinger定理可以归因于所采用的单粒子格林函数的缺点或误用这个定理。一个例外的情况带来了一个真正的失败的可能性,绝缘基态的Luttinger定理,我们表明,这是由一个错误的限制,在原则上可以达到采取零温度极限,没有符合的值μ的零温度极限的化学势满足状态方程在有限的温度;对于金属态不会出现这种模糊性。

英文摘要:

We analyze the original proof by Luttinger and Ward of the Luttinger theorem, according to which for uniform ground states of systems of (interacting) fermions, which may be metallic or insulating, the number of k points corresponding to non-negative values of G_s(k;mu) is equal to the total number of particles with spin index s in these ground states. Here G_s(k;mu) is the single-particle Green function of particles with spin index s at the chemical potential mu. For the cases where the two-body interaction potential is short-range, and in particular for lattice models, we explicitly demonstrate that this theorem is unconditionally valid, irrespective of the strength of the bare interaction potential. We arrive at this conclusion by amongst other things demonstrating that the perturbation series expansion for self-energy in terms of skeleton diagrams, as encountered in the proof of the Luttinger-Ward identity, is uniformly convergent for almost all momenta and energies. We further investigate the mechanisms underlying some reported instances of failure of the Luttinger theorem. With one exception, for all the cases considered in this paper, we show that the apparent failures of the Luttinger theorem can be attributed either to shortcomings of the employed single-particle Green functions or to misapplication of this theorem. The one exceptional case brings to light the possibility of a genuine failure of the Luttinger theorem for insulating ground states, which we show to be brought about by a false limit that in principle can be reached on taking the zero-temperature limit without the value of mu coinciding with the zero-temperature limit of the chemical potential satisfying the equation of state at finite temperatures; no such ambiguity can arise for metallic states.

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