Negative differential resistance in all-benzene molecule of trefoil knot

Abstract

Based on first-principles calculations, the electronic transport of a recently synthesized all-benzene molecule of trefoil knot is investigated, by contacted with Au electrodes. Negative differential resistance behavior is observed. Further analysis shows that, it is resulted from the weaken of the states on the molecule modulated by the bias voltage, which suppresses the transmission eigenchannels and transmission peaks. Moreover, such a NDR behavior is also found in knot molecules with more benzene rings, indicating NDR is the intrinsic feature of such kind of molecules and robust to the number of benzene rings. These findings are expected to be extended to many other molecules with similar geometries, and may throw light on the development of future nanodevices.

Introduction

Due to the development of nanotechnology and molecular synthesis, molecular electronics have been paid much attention in recent years [1], [2]. Using a single molecule to design and build a functional device is the ultimate goal in this area [3]. Up to now, kinds of interesting electronic phenomena have been revealed in molecule and related systems, such as negative differential resistance (NDR) [4], [5], [6], [7], molecular rectification [8], [9], [10], highly nonlinear current-voltage ($I-V$) characteristics [11], switching [12], [13], [14], Zitterbewegung effect [15], tunable topological states [16], Kondo metal and ferrimagnetic insulator [17], and etc. Due to the superior geometric and electronic properties, e.g., good flexibility, high thermal stability, and high carrier mobility, carbon-based nanostructures are expected to be one of the most promising candidates for future nanoelectronic devices [18], [19].

Recently, Segawa et al. [20] achieved the synthesis of catenanes and a molecular trefoil knot in experiment, which consist solely of para-connected benzene rings. Peculiar dynamic behaviors, such as rapid vortex-like motion, of the knot have been observed, which have been theoretically predicted before [20]. Catenanes are a kind of molecular geometry with two or more interlocking macrocycles. And a trefoil knot is a molecular architecture that resembles a knot possessing three crossings.

Different from other carbon nanostructures reported before, the interactions in the molecule are more interesting [21], [22]. Especially, for the trefoil knot, the whole molecule can be seen as twisted by a single benzene chain. There are not only intra-chain interactions, but also inter-chain interactions. In other words, the chain interacts with itself, which may trigger interesting electronic behaviors [23]. Moreover, such a molecule exhibits a distinct spacial geometry with high symmetries. The research on it may throw light on the understanding of these all-benzene knot molecules, and also open a new way to utilize them for novel devices' fabrications. However, the study on it is still lacking.

In the present work, based on first-principles calculations [24], the electronic transport of a molecular trefoil knot consisting solely of para-connected benzene rings is investigated, which is contacted by Au electrodes. Negative differential resistance behavior is observed. Further analysis shows that, it is caused by the weaken of the states on the molecule, which is modulated by the bias voltage. And the weaken suppresses the transmission eigenchannels and transmission peaks. Moreover, such a NDR behavior is also observed in knot molecules with more benzene rings, which means NDR is the intrinsic feature of such kind of molecules and robust to the number of benzene rings. We believe these findings are quite beneficial for the developing of molecular devices, showing great application potential.