具有自旋-轨道Rashba相互作用的二维Fröhlich极化子的弱耦合和强耦合极限
Weak and strong coupling limits of the two-dimensional Fröhlich polaron with spin-orbit Rashba interaction
摘要：
在制造具有大自旋轨道耦合的低维系统方面的不断进展已经达到了一个点，即现在的材料可以显示从几个到几百个meV的自旋轨道分裂能量。这种情况要求更好地理解自旋轨道耦合和固体中普遍存在的其他相互作用之间的相互作用，特别是当自旋轨道分裂的大小与特征能量尺度（如费米能量和声子频率）相当时。在这篇文章中，二维Fröhlich电子-声子问题是通过引入耦合到一个自旋-轨道Rashba势，允许对电子-声子相互作用的自旋-轨道效应的描述重新制定。在电子-声子相互作用的弱耦合极限和强耦合极限下，研究了任意自旋-轨道分裂值的Fröhlich-Rashba极化子的基态.弱耦合的情况下进行了研究的瑞利-薛定谔微扰理论，而强耦合的电子-声子制度的研究通过变分极化子波函数在绝热极限。结果表明，无论是弱耦合还是强耦合极化子，自旋轨道相互作用都使其基态能量降低，说明Rashba耦合增强了极化子的性质.它还表明，一致的基态的降低，极化子的有效质量增强相比，零自旋轨道极限。最后，讨论了自旋轨道相互作用可以改变弱耦合极化子和强耦合极化子之间的交叉。
英文摘要：
The continuous progress in fabricating low-dimensional systems with large spin-orbit couplings has reached a point in which nowadays materials may display spin-orbit splitting energies ranging from a few to hundreds of meV. This situation calls for a better understanding of the interplay between the spin-orbit coupling and other interactions ubiquitously present in solids, in particular when the spin-orbit splitting is comparable in magnitude with characteristic energy scales such as the Fermi energy and the phonon frequency. In this article, the two-dimensional Fröhlich electron-phonon problem is reformulated by introducing the coupling to a spin-orbit Rashba potential, allowing for a description of the spin-orbit effects on the electron-phonon interaction. The ground state of the resulting Fröhlich-Rashba polaron is studied in the weak and strong coupling limits of the electron-phonon interaction for arbitrary values of the spin-orbit splitting. The weak coupling case is studied within the Rayleigh-Schrödinger perturbation theory, while the strong-coupling electron-phonon regime is investigated by means of variational polaron wave functions in the adiabatic limit. It is found that, for both weak and strong coupling polarons, the ground state energy is systematically lowered by the spin-orbit interaction, indicating that the polaronic character is strengthened by the Rashba coupling. It is also shown that, consistently with the lowering of the ground state, the polaron effective mass is enhanced compared to the zero spin-orbit limit. Finally, it is argued that the crossover between weakly and strongly coupled polarons can be shifted by the spin-orbit interaction.
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