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arXiv 2201.10199cond-mat.mes-hall
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窄禁带碳纳米管中的反常屏蔽

Anomalous screening in narrow-gap carbon nanotubes

Giacomo Sesti, Daniele Varsano, Elisa Molinari, Massimo Rontani

摘要:

库仑相互作用的屏蔽控制着碳纳米管中的多体物理学,因为它调节了作用于载流子并将电子空穴对束缚成激子的力的范围和强度。在掺杂管中,有效库仑相互作用驱动Luttinger液体和Wigner晶体之间的竞争,而在未掺杂的窄隙管中,它决定了低温下观察到的相关绝缘体的Mott或激子性质。在这里,通过计算选定的窄和零间隙管从第一原理的介电函数,我们表明,标准的有效质量模型的筛选系统低估了在长波长的相互作用强度,因此错过了低能量激子的结合。原因是该模型严重缺乏管的完整三维拓扑结构,这是根据石墨烯理论改编的。由于从头计算仅限于小的管,我们开发了一个双带模型的基础上的平面波展开的布洛赫状态和精确的截断库仑截断技术的介电函数。我们证明,我们的计算成本低的方法提供了正确的筛选任何大小和手性的窄间隙管。一个引人注目的结果是,屏蔽相互作用仍然是长程的,即使在无间隙管,作为由弯曲的管表面上移动的电子所产生的微观局部场的效果。作为一个应用,我们表明,有效的电子-电子力,感觉到在距离相关的量子传输实验是超库仑。

英文摘要:

The screening of Coulomb interaction controls many-body physics in carbon nanotubes, as it tunes the range and strength of the force that acts on charge carriers and binds electron-hole pairs into excitons. In doped tubes, the effective Coulomb interaction drives the competition between Luttinger liquid and Wigner crystal, whereas in undoped narrow-gap tubes it dictates the Mott or excitonic nature of the correlated insulator observed at low temperature. Here, by computing the dielectric function of selected narrow- and zero-gap tubes from first principles, we show that the standard effective-mass model of screening systematically underestimates the interaction strength at long wavelength, hence missing the binding of low-energy excitons. The reason is that the model critically lacks the full three-dimensional topology of the tube, being adapted from graphene theory. As ab inito calculations are limited to small tubes, we develop a two-band model dielectric function based on the plane-wave expansion of Bloch states and the exact truncated Coulomb cutoff technique. We demonstrate that our -- computationally cheap -- approach provides the correct screening for narrow-gap tubes of any size and chirality. A striking result is that the screened interaction remains long-ranged even in gapless tubes, as an effect of the microscopic local fields generated by the electrons moving on the curved tube surface. As an application, we show that the effective electron-electron force that is felt at distances relevant to quantum transport experiments is super Coulombic.

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。

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