Profeta G, Tosatti E
CNISM and Dipartimento di Fisica, Università degli Studi di L'Aquila, I-67010 Coppito (L'Aquila), Italy.
Phys Rev Lett. 2007 Feb 23;98(8):086401. doi: 10.1103/PhysRevLett.98.086401. Epub 2007 Feb 21.
The ground state of Sn/Si(111) and Sn/Ge(111) surface alpha phases is reexamined theoretically, based on ab initio calculations where correlations are approximately included through the orbital dependence of the Coulomb interaction (in the local density+Hubbard U approximation). The effect of correlations is to destabilize the vertical buckling in Sn/Ge(111) and to make the surface magnetic, with a metal-insulator transition for both systems. This signals the onset of a stable narrow gap Mott-Hubbard insulating state, in agreement with very recent experiments. Antiferromagnetic exchange is proposed to be responsible for the observed Gamma-point photoemission intensity, as well as for the partial metallization observed above 60 K in Sn/Si(111). Extrinsic metallization of Sn/Si(111) by, e.g., alkali doping, could lead to a novel 2D triangular superconducting state of this and similar surfaces.
基于从头算计算，在库仑相互作用的轨道依赖性（局部密度+哈伯德U近似）中近似包含相关性的情况下，对Sn/Si(111)和Sn/Ge(111)表面α相的基态进行了理论重新研究。相关性的影响是使Sn/Ge(111)中的垂直屈曲不稳定，并使表面具有磁性，两个系统都发生金属-绝缘体转变。这标志着稳定的窄带隙莫特-哈伯德绝缘态的开始，与最近的实验结果一致。反铁磁交换被认为是观察到的Γ点光发射强度以及Sn/Si(111)中60K以上观察到的部分金属化的原因。例如，通过碱掺杂对Sn/Si(111)进行外部金属化，可能会导致该表面和类似表面出现新型二维三角超导态。
