Fine Theoretical Physics Institute, University of Minnesota, Minneapolis, Minnesota 55455, USA.
Phys Rev Lett. 2012 Oct 26;109(17):176801. doi: 10.1103/PhysRevLett.109.176801. Epub 2012 Oct 23.
As-grown topological insulators (TIs) are typically heavily doped n-type crystals. Compensation by acceptors is used to move the Fermi level to the middle of the band gap, but even then TIs have a frustratingly small bulk resistivity. We show that this small resistivity is the result of band bending by poorly screened fluctuations in the random Coulomb potential. Using numerical simulations of a completely compensated TI, we find that the bulk resistivity has an activation energy of just 0.15 times the band gap, in good agreement with experimental data. At lower temperatures activated transport crosses over to variable range hopping with a relatively large localization length.
原生拓扑绝缘体（TI）通常是高度掺杂的 n 型晶体。通过受主补偿将费米能级移动到能带隙中间，但即使这样，TI 的体电阻仍然令人沮丧地小。我们表明，这种小电阻是由随机库仑势中未被屏蔽的涨落引起的能带弯曲的结果。通过对完全补偿的 TI 的数值模拟，我们发现体电阻的激活能仅为带隙的 0.15 倍，与实验数据吻合良好。在较低温度下，激活输运转变为具有较大局域化长度的变程跳跃。
