Origin of torsion-induced conductance oscillations in carbon nanotubes

Abstract

We combine electromechanical measurements with ab initio density-functional calculations to settle the controversy about the origin of torsion-induced conductance oscillations in multiwall carbon nanotubes. Contrary to intuition, the observed oscillation period in multiwall tubes exhibits the same inverse-squared diameter dependence as in single-wall tubes with the same diameter. This finding suggests an intrawall origin of the oscillations and an effective electronic decoupling of the walls, which we confirm in calculations of multiwall nanotubes subject to differential torsion. We exclude the alternative origin of the conductance oscillations due to changes in the interwall registry, which would result in a different diameter dependence of the oscillation period.

Quantifying the Stacking Registry Matching in Layered Materials

“…[19][20][21][22][23][24][25][26][27][28][29][30] When stacked together to form multilayered structures, the physical properties of the individual layers may be considerably altered via interlayer interactions. [31][32][33][34][35][36][37][38][39][40][41][42][43][44][45] Due to the different nature of the intra-and inter-layer interactions, the resulting layered systems often present highly anisotropic properties. Within each layer covalent bonding usually results in relatively high strength and stiffness [8][9][10]46] along the direction of the layer and, in some cases, in efficient electronic [9][10][11]47] and heat [48][49][50][51][52][53][54][55][56][57][58][59]…”

“…In such systems, apart from the specific chemical composition of the nanotube, which dictates the nature of the interlayer interactions, curvature differences and different rolling orientations (chiral angles) of adjacent layers result in complex registry matching and mismatching patterns often regarded as Moiré fringes. [44] It is therefore clear that registry matching plays an important role in dictating the electronic properties of layered materials and in the interlayer sliding physics of such systems. [35,36,45,[67][68][69][70][71][72][73][74][75][76][77] Nevertheless, previous studies concerning such effects have regarded the registry matching in qualitative terms labeling it as "bad", "good", or "optimal" according to the relative energetic stability of the different stacking modes as calculated by either force fields [62,78] or via electronic structure theories.…”

Electronic properties of carbon nanotubes with distinct bond lengths

“…34 For torsion, failure is at approximately tan ␣ = 0.2-0.3 in multiwalled CNT. 11,35 There is some evidence that it is the outermost wall of a multiwalled CNT that carries the majority of the current and torque, 11,36 and for this reason we may be able to assume that the hopping between walls is very small, relative to the hopping within the outermost wall. If this is the case then the results derived here for single walled CNT may also be applicable to multiwalled CNT.…”

Electronic and optical properties of deformed graphitic and helical nanobutes

“…Elektromehaničke osobine su podvrgnute i eksperimantalnom ispitivanju [41,42,43,44,45]. Predmet merenja su električni transport nanotuba izoženih podužnim [41,42] ili torzionim deformacijama [43,44,45].…”

“…Predmet merenja su električni transport nanotuba izoženih podužnim [41,42] ili torzionim deformacijama [43,44,45]. Metod primenjen u slučaju podužno deformisanih tuba je direktno deformisanje tube AFM vrhom kaošto je prikazano na slici 2.1 (a).…”