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arXiv 1809.08347cond-mat.mes-hall
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碳纳米管中相互作用驱动的巨轨道磁矩

Interaction-driven giant orbital magnetic moments in carbon nanotubes

Joshua O. Island, Marvin Ostermann, Lee Aspitarte, Ethan D. Minot, Daniele Varsano, Elisa Molinari, Massimo Rontani, Gary A. Steele

摘要:

碳纳米管仍然是研究约束和相互作用的模型系统。这在所谓的“超净”碳纳米管设备的情况下尤其如此,该设备提供了对具有极低无序度的量子点的研究。然而,这些系统的质量越来越多地暴露出实验与理论之间的明显差异。在这里,我们解决了碳纳米管量子点中异常大的轨道磁矩的突出异常。我们进行低温磁输运测量的轨道磁矩,并发现它是7倍以上的预期从传统的半经典模型。此外,磁矩的大小随着每个电子添加到量子点而单调下降,这直接与广泛接受的单粒子能级的壳填充图相矛盾。我们进行准粒子计算,无论是从第一原理和有效质量近似,并发现巨磁矩只能通过考虑自能校正的电子能带结构,由于电子-电子相互作用被捕获。

英文摘要:

Carbon nanotubes continue to be model systems for studies of confinement and interactions. This is particularly true in the case of so-called "ultra-clean" carbon nanotube devices offering the study of quantum dots with extremely low disorder. The quality of such systems, however, has increasingly revealed glaring discrepancies between experiment and theory. Here we address the outstanding anomaly of exceptionally large orbital magnetic moments in carbon nanotube quantum dots. We perform low temperature magneto-transport measurements of the orbital magnetic moment and find it is up to seven times larger than expected from the conventional semiclassical model. Moreover, the magnitude of the magnetic moment monotonically drops with the addition of each electron to the quantum dot directly contradicting the widely accepted shell filling picture of single-particle levels. We carry out quasiparticle calculations, both from first principles and within the effective-mass approximation, and find the giant magnetic moments can only be captured by considering a self-energy correction to the electronic band structure due to electron-electron interactions.

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