氮化硼纳米片的电子结构和自旋调控

Electronic structure and spin-polarization of boron-nitride nanoflake

单层氮化硼纳米材料具有与石墨烯相似的原子排列方式,但是由于硼原子和氮原子之间的电荷转移,两种材料的电子特性具有较大的差异.本文采用Hubbard模型和量子力学第一性原理计算相结合的方法研究了具有氢原子饱和的锯齿型边界的三角形氮化硼纳米片(Nanoflake)的电子结构,发现:与相应的石墨烯纳米片不同,出现在氮化硼纳米片费米能级附近的零能态(zero-energy-states)要么被电子完全占据,要么是全空的,表现出自旋简并的特点;通过对氮化硼纳米片进行电子(或空穴)掺杂可以有效地调控"零能态"上的电子占据,进而对氮化硼纳米片的自旋进行调控.这将为氮化硼纳米材料在自旋电子学等领域的应用提供重要的理论依据.

Boron-nitride graphene-like monolayer possesses a similar atomic arrangement to that of the famous graphene. However, due to the large difference in electronegetivity between boron and nitrogen atoms, the electronic properties of the two nanomaterials are different significantly. Here, we report on our theoretical investigation of the electronic structure and spin-polarization of zigzag-edged boron-nitride triangular nanoflake using a Hubbard model and the first-principles calculations within density-functional theory. Our numerical results indicate that in contrast to graphene nanoflake with spin-polarized ground state, the boron-nitride nanoflak has the zero-energy state that is either empty or fully occupied, and its ground state is thus spin-unpolarized which breaks the Lieb＇s law. However, the electron occupation and spin-polarization of the zero-energy state of boron-nitride nanoflake can be tuned by doping it with electrons or holes. These results are expected to offer the theoretical basis for the applications of boron-nitride nanomaterials in spintronics.