Half‐Metallic Carbon Nanotubes

Abstract

Half-metallicity in carbon nanotubes is achieved and controlled by hydrogen adsorption patterns. The edge states in carbon nanotubes are unstable under an electric field due to the spin-conserving electron transfer between the edges, but a large enough transfer barrier between the edge states, obtained by controlling the adsorption patterns, renders the CNTs half-metallic.

Recent advances in Dirac spin-gapless semiconductors

“…However, there are still many issues to be resolved, such as the generation and injection of the spin-polarized carrier, the manipulation and detection of the spin direction, and the long-distance spin-polarized transport. [1][2][3] Researchers have proposed various concepts or spintronic materials to address these problems, including half-metals (HMs), [4][5][6][7][8] topological insulators (TIs), [9][10][11][12][13][14] magnetic semiconductors (MSs), [15][16][17][18] and spin-gapless semiconductors (SGSs).…”

Edge-state magnetism in hydrogenated armchair carbon nanotubes

“…While antiferromagnetic edge states are necessary for the electric field-induced half-metallicity in ZGNRs, the exchange energy gain stabilizing the antiferromagnetism in ZGNRs is at best several meV and further decreases with increasing ZGNR width [6], indicating that the half-metallicity can be realized only at very low temperatures. Recently, half-metallicity was also predicted in hydrogenated carbon nanotubes (CNTs) under an electric field [7], the antiferromagnetic edge states created by hydrogen adsorption also being an origin of the half-metallicity. In this work, we investigated the antiferromagnetic edge states in hydrogenated CNTs by using the density functional theory (DFT) calculations.…”

“…According to the spin alternation mechanism in graphene that neighboring sites should have opposite spins [12,13], the spin configuration resulting from the H-lines can be predicted. The two H-lines at different sublattices lead to the antiferromagnetic edge states and divide the pbond network into two parts [7,14,15], each of which has zigzag (ZE) and bearded (BE) edges as shown in Fig. 1.…”

“…According to a previous work [7], the (n,n)CNT with two H-lines at different sublattices will be designated as (n,n)CNT-HNz (N 2nÀ1), where N is the number of CeC dimers along the circumference in the BE part. Fig.…”

Edge states in horseshoe-shape carbon nanotubes transformed by hydrogen adsorption

“…9,10 Adsorption of two H atoms per unit cell on a C-C pair being aligned along the tube axis gives rise to antiferromagnetic edge states in armchair (n,n)CNTs. 11, 12 On the other hand, adsorption of two H atoms per unit cell on a C-C pair being aligned normal to the nanotube axis will transform the armchair CNT into a horseshoe shape. [3][4][5] A C-C bond normal to the tube axis (along the circumference) is under a strong tension, making it weaker than that along the tube axis.…”