arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 1602.02649cond-mat.mes-hallcond-mat.mtrl-sci
收藏

拓扑绝缘体Bi2Se3和Bi2Te3中PDKEEPAAA位移的紧束缚理论

Tight-binding theory of NMR shifts in topological insulators Bi2Se3 and Bi2Te3

Samuel Boutin, Jorge Ramírez-Ruiz, Ion Garate

摘要:

受最近的核磁共振(NMR)实验的启发,我们提出了一个微观的sp3紧束缚模型计算的NMR位移在散装Bi 2Se 3,Bi 2 Te 3。我们计算的接触,偶极,轨道和核心极化的贡献的载流子密度依赖的一部分,在Bi 209,Te 125和Se 77的NMR位移。自旋-轨道耦合和层状晶体结构导致了具有强单轴各向异性的接触Knight位移。同样地,由于自旋-轨道耦合,偶极相互作用对NMR位移的各向同性部分做出显著贡献。在Bi 209 NMR中,尽管费米能级上的电子态具有相当弱的s轨道特征,但接触相互作用主导了各向同性Knight位移。与此相反,从接触超精细相互作用的贡献的NMR位移的Se 77和Te 125是弱的偶极和轨道位移相比。在所有情况下,轨道移动至少与接触和偶极移动相当,而由于核心极化的移动是次显性的(除了位于反转中心的Te核)。通过人为地改变自旋轨道耦合的强度,我们评估了整个带反转的NMR位移的演变,但没有发现明确的拓扑转变的签名。

英文摘要:

Motivated by recent nuclear magnetic resonance (NMR) experiments, we present a microscopic sp3 tight-binding model calculation of the NMR shifts in bulk Bi2Se3, and Bi2Te3. We compute the contact, dipolar, orbital and core polarization contributions to the carrier-density-dependent part of the NMR shifts in Bi209, Te125 and Se77. The spin-orbit coupling and the layered crystal structure result in a contact Knight shift with strong uniaxial anisotropy. Likewise, because of spin-orbit coupling, dipolar interactions make a significant contribution to the isotropic part of the NMR shift. The contact interaction dominates the isotropic Knight shift in Bi209 NMR, even though the electronic states at the Fermi level have a rather weak s-orbital character. In contrast, the contribution from the contact hyperfine interaction to the NMR shift of Se77 and Te125 is weak compared to the dipolar and orbital shifts therein. In all cases, the orbital shift is at least comparable to the contact and dipolar shifts, while the shift due to core polarization is subdominant (except for Te nuclei located at the inversion centers). By artificially varying the strength of spin-orbit coupling, we evaluate the evolution of the NMR shift across a band inversion but find no clear signature of the topological transition.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

↑