Electrical transport in deformed nanostrips : electrical sig - nature of reversible mechanical failure

– We calculate the electrical conductivity of a thin crystalline strip of atoms confined within a quasi one dimensional channel of fixed width. The conductivity shows anomalous behavior as the strip is deformed under tensile loading. Beyond a critical strain, the solid fails by the nucleation of alternating bands of solid and smectic like phases accompanied by a jump in the conductivity. Since the failure of the strip in this system is known to be reversible, the conductivity anomaly may have practical use as a sensitive strain transducer. Introduction: Deformation of nano meter sized wires and bars have been studied, using theoretical analysis as well as experiments, extensively in recent times [1–3]. Such studies are useful both for understanding deformation mechanisms in general and for their relevance in the construction of nano devices [2]. Single crystal nano bars and strips have been shown to fail on tensile loading conditions by the familiar necking mechanism [3] where an elastic instability leads to a reduction of the cross section of bar. While necking in bulk samples [4] occurs along with extensive plastic deformation caused by the motion of dislocations, in nano strips and beams, dislocations cannot be nucleated because of much higher elastic energy costs [5]. This leads to novel layering transitions where the solid thins down layer by layer [3] and finally fractures after attaining the thickness of an atomic chain. The situation is somewhat different if the nano sized solid is confined within a rigid channel [6] so that the necking transition is prevented. In this case, with imposition of an external strain parallel to the confining walls, the solid fails by a series of layer transitions where the number of crystalline layers decreases by one, accompanied by the nucleation of bands of a fluid with strong orientational order. The remarkable fact is that this transition is completely reversible, such that a decrease of the tensile strain, immediately causes these failure bands to disappear and the solid heals itself automatically. In this Letter, we look at the electrical conductivity (∗) E-mail:[email protected] (∗∗) E-mail:[email protected] (∗∗∗) E-mail:[email protected] (∗∗∗) E-mail:[email protected]