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arXiv 1606.09435cond-mat.mtrl-scicond-mat.mes-hallcond-mat.supr-con
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石墨烯中的动力学电荷和赝自旋流以及可能的库珀对形成

Dynamical charge and pseudospin currents in graphene and possible Cooper pair formation

K. Morawetz

摘要:

基于SU(2)结构体系的量子动力学方程,计算了石墨烯中的无正则化密度和赝自旋流,将其实现为具有二次色散和适当自旋轨道耦合的无限质量极限电子。相应地,电流没有准粒子部分,只有反常部分。带内和带间电导率相对于磁场和磁畴水坑进行了讨论。结果表明,磁畴的磁场和平均场可以用一个有效塞曼场来表示。对于大的塞曼场,动态电导率变得与密度无关,并且在这个意义上是普遍的。消失密度、弛豫、频率和塞曼场的不同极限是不可互换的。利用屏蔽杂质散射和有效塞曼场,得到的电导率与实验值吻合得很好。的霍尔电导率的普遍值示出被修改,由于塞曼场。赝自旋流揭示了一个异常,因为准粒子部分出现,虽然它消失的粒子流。密度和赝自旋响应函数的外部电场的计算和介电函数进行了讨论相对于集体激发。确定的频率和波矢量范围内的介电函数的变化的符号和排斥库仑势变得有效地吸引力允许库珀配对。

英文摘要:

Based on the quantum kinetic equations for systems with SU(2) structure, regularization-free density and pseudospin currents are calculated in graphene realized as the infinite mass-limit of electrons with quadratic dispersion and a proper spin-orbit coupling. Correspondingly the currents possess no quasiparticle part but only anomalous parts. The intraband and interband conductivities are discussed with respect to magnetic fields and magnetic domain puddles. It is found that the magnetic field and meanfield of domains can be represented by an effective Zeeman field. For large Zeeman fields the dynamical conductivities become independent of the density and are universal in this sense. The different limits of vanishing density, relaxation, frequency, and Zeeman field are not interchangeable. The optical conductivity agrees well with the experimental values using screened impurity scattering and an effective Zeeman field. The universal value of Hall conductivity is shown to be modified due to the Zeeman field. The pseudospin current reveals an anomaly since a quasiparticle part appears though it vanishes for particle currents. The density and pseudospin response functions to an external electric field are calculated and the dielectric function is discussed with respect to collective excitations. A frequency and wave-vector range is identified where the dielectric function changes sign and the repulsive Coulomb potential becomes effectively attractive allowing Cooper pairing.

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