Excitonic effects in two-dimensional massless Dirac fermions
Excitonic effects in two-dimensional massless Dirac fermions
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DOI：
10.1103/physrevb.83.035404
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发表时间：
2010-10
影响因子：
3.7
通讯作者：
Jianhui Wang;H. Fertig;G. Murthy;L. Brey
中科院分区：
文献类型：
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作者：
Jianhui Wang;H. Fertig;G. Murthy;L. Brey
我们通过求解 Bethe-Salpeter 方程的阶梯近似来研究具有库仑相互作用的二维无质量狄拉克费米子中的激子效应。研究发现，一般四腿顶点具有幂律行为，随着耦合常数的增加，指数由实数变为复数。这种行为的变化体现在反对称响应中，它在小波矢量处表现出幂律行为，让人想起临界状态，并且幂律从实数到复数的变化伴随着有限尺寸系统的响应函数中的极点，这表明存在足够强的相互作用的相变。还计算了密度-密度响应，但没有发现关键行为。我们证明，激子相关性增强了 $2{k}_{F}$ 处不可约极化率的尖点，导致带电杂质周围的弗里德尔振荡振幅大幅增加。
We study excitonic effects in two-dimensional massless Dirac fermions with Coulomb interactions by solving the ladder approximation to the Bethe-Salpeter equation. It is found that the general four-leg vertex has a power-law behavior with the exponent going from real to complex as the coupling constant is increased. This change of behavior is manifested in the antisymmetric response, which displays power-law behavior at small wave vectors reminiscent of a critical state, and a change in this power law from real to complex that is accompanied by poles in the response function for finite-size systems, suggesting a phase transition for strong enough interactions. The density-density response is also calculated, for which no critical behavior is found. We demonstrate that exciton correlations enhance the cusp in the irreducible polarizability at $2{k}_{F}$, leading to a strong increase in the amplitude of Friedel oscillations around a charged impurity.