Theoretical Design Of One-dimensional Te Nanomaterials

Due to the unique crystal structure and physicochemical properties,onedimensional(1D)materials show attractive prospects in the fields of electronic devices and spintronics.Among them,1D atomic chains and 1D nanowires are considered as the most promising materials.The Te bulk is assembled by 1D chemical-bonded atomic chains through van der Waals forces,which provides the possibility to design atomic level 1D chains and 1D composite nanowires.Moreover,the Te atomic chain exhibits a helical asymmetric structure,which can undergo large structural deformation without damage.Notably,the 1D Te-based nanomaterials in experiments usually consist of the multiple Te chains rather than a single one.Furthermore,they are often confined in nanotubes,because the environment will impair the stability and electronic structure of free Te chains.This presents a series of challenges to the development and application of 1D Te nanomaterials:(1)understanding the intrinsic atomic and electronic structures of the single Te atomic chain and its structural deformation mechanism;(2)revealing the coupling effect between the multiple Te chains;(3)clarifying the confinement effect of nanotubes on the single Te atom chain.To address these issues,we designed three structural models: single Te chain,multiple Te chains,and single Te chain confined in nanotubes,which are detailed as follows:1.The intrinsic properties of a Te atomic chain and its response mechanism toward strainWe focus on the single Te chains with strict 1D characteristics,which exhibit a large Rashba spin splitting among the known 1D systems and their splitting parameters depend strongly on the strain and structural distortion.This can be attributed to the helical structures of atomic Te chains,which not only sustain significant strain without damage but also realize the synergy of orbital angular momentum and in-chain potential gradient in enhancing spin splitting.The structural distortion of stretched helical Te chains is critical to executing this synergy,generating a large Rashba spin splitting among the known systems.Our findings propose a potential 1D giant Rashba splitting system for exploring spintronics and Majorana fermions and provide routes for engineering spin splitting in other materials.2.The interchain coupling effect between the multiple Te chains.We investigate the effects of the chirality,size,and stacking mode on the stability and electronic properties of the few-chain Te nanowires.The phonon spectra and interchain binding energies suggest that the few-chain Te nanowires are stable.We find that the bulk stacking mode and larger size always lead to higher stability,regardless of the chirality.In addition,the band gap and Rashba parameters decrease with the increase of the number of chains.Furthermore,changing the chirality and the stacking mode can adjust the value of the band gap and Rashba parameters of the 1D helical Te chains.These phenomena are mainly due to the quantum size effect and the special helical structure of the Te atomic chains.Our findings provide a simple way to adjust the electronic structure of the Te atomic chains,which can serve as the basis for the development of new nano electronic devices.3.The confinement effect on the atomic and electronic structures of the single Te chain confined in nanotubes.We systematically explore the effects of size and chirality on the atomic and electronic structures of the Te chains confined in CNTs/BNNTs with density functional theory.We find that the configurations of confined Te chains depend strongly on the tube size,but weakly on its chirality and type.Te@BNNTs show giant Rashba splitting with the Rashba constant up to 2.65 e V (?),which is the highest among known pure 1D systems,while Te@CNTs show no Rashba splitting.Because the large bandgaps of BNNTs accommodate and maintain the band edges of Te chains,while CNTs with zero bandgaps fail to do that.Our findings provide a basis for the construction of nano spin devices and lay a foundation for the design of new nanoelectronic devices.