Electronic states of SnTe and PbTe (001) monolayers with supports

Electronic states of SnTe and PbTe (001) monolayers are theoretically studied by density-functional calculations. The systems investigated are freestanding monolayers, monolayers on NaBr substrates, and monolayers sandwiched between two NaBr surfaces. Though isolated PbTe monolayers assumed in a planar structure have the edge states that suggest topological crystalline insulating states, the planar structure of freestanding monolayers is unstable and the mirror symmetry is lost by buckling. Calculations of monolayers on NaBr substrates show that though the attractive interaction between monolayers and substrates reduces buckling amplitude in monolayers, substrates produce a new asymmetry of electrostatic potential in monolayers. Theoretical calculations show that the SnTe monolayers sandwiched between two NaBr surfaces have the edge states suggesting that they are two-dimensional topological crystalline insulators. (C) 2015 Elsevier B.V. All rights reserved.