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首页> 外文期刊>Physica Scripta: An International Journal for Experimental and Theoretical Physics >Electron spin in single wall carbon nanotubes
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Electron spin in single wall carbon nanotubes

机译：单壁碳纳米管中的电子自旋

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We review aspects of electrical transport in metallic single wall carbon nanotubes (SWCNT) related to the spin of the conductance electrons. For large contact resistances. R much greater than h/2e(2). a SWCNTexhibits Coulomb blockade. and transmission can only occur, when a gate voltage leads to an energy degeneracy for two different numbers of electrons in the SWCNT The Coulomb blockade gate voltage change is directly proportional to the addition energy for single electron tunnelling. In certain ideal cases every second of the populated electronic states has a higher addition energy. indicating that two spin-degenerate electrons are roomed at each orbital state. A low addition energy therefore corresponds to approaching an even number of electrons. The odd-even alternation can be checked in a magnetic field. since then the odd additional electron may enter in one of two Zeeman states. If the high resistance contact is a tunnel junction. the transmission reflects the density of states. This leads to a direct detection of the so-called Luttinger liquid state of the electrons. Ferromagnetic contacts to the SWCNT leads to a conductance which depends on the orientation of the magnetic domains in the contacts. The magnetoresistance effect can be much larger than expected from a simple spin-valve phenomenon. For any intermediate normal metal (Au) contact resistances, R similar to h/2e(2) the Coulomb blockade may still separate the single electron states in the SWCNT with odd and even numbers of electrons. However. at the lowest temperatures the transmission only shows Coulomb blockade for even number of electrons. In the situations with odd number of electrons a coherent tunnelling process dominates. This shortage of the blockade is rooted in the Kondo states formed in the two Au electrodes by exchange interaction due to the spin state in the SWCNT This tunnelling process is a result of a net spin on the SWCNT and consequently a spin degeneracy A triplet state is forced into degeneracy with the singlet state in a suitable magnetic field. The situation in a magnetic field is particularly simple in a SWCNT in contrast to conventional quantum dots, because the tiny diameter of the SWCNT practically speaking precludes orbital effects. [References: 41]
机译：我们回顾了与电导电子的自旋有关的金属单壁碳纳米管（SWCNT）中的电传输方面。对于较大的接触电阻。 R远大于h / 2e（2）。 SWCNT表现出库仑封锁。只有当栅极电压导致SWCNT中两个不同数量的电子的能量简并时，传输才可能发生。库仑阻塞栅极电压的变化与单电子隧穿的附加能量成正比。在某些理想情况下，每秒钟填充的电子状态具有较高的附加能量。表示两个自旋简并电子在每个轨道状态下都存在因此，低的附加能量相当于接近偶数个电子。可以在磁场中检查奇偶交替。从那时起，奇数附加电子可能会进入两个塞曼状态之一。如果高电阻触点是隧道结。传输反映了状态的密度。这导致直接检测所谓的电子的卢汀格液态。与SWCNT的铁磁接触导致电导，该电导取决于接触中磁畴的方向。磁阻效应可能比简单的自旋阀现象所预期的要大得多。对于任何中间的普通金属（Au）接触电阻，R类似于h / 2e（2），库仑封锁仍可能用奇数和偶数电子分隔SWCNT中的单电子态。然而。在最低温度下，透射率仅显示偶数电子的库仑阻挡。在电子数量奇数的情况下，相干隧穿过程占主导地位。这种阻碍的缺乏根源于两个金电极中由于SWCNT中的自旋态通过交换相互作用形成的近藤状态。这种隧穿过程是SWCNT上净自旋的结果，因此自旋简并性是三重态。在适当的磁场中以单重态被迫简并。与传统的量子点相比，SWCNT中的磁场情况特别简单，因为从实际上讲，SWCNT的微小直径可排除轨道效应。 [参考：41]

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