Evidence for a positron bound state on the surface of a topological insulator

[摘要] We describe experiments aimed at probing the sticking of positrons to the surfaces of topological insulators using the Positron Annihilation induced Auger Electron Spectrometer (PAES). A magnetically guided beam was used to deposit positrons at the surface of Bi2Te2Se sample at energy of ∼2eV. Peaks observed in the energy spectra and intensities of electrons emitted as a result of positron annihilation showed peaks at energies corresponding to Auger peaks in Bi, Teand Se providing clear evidence of Auger emission associated with the annihilation of positrons in a surface bound state. Theoretical estimates of the binding energy of this state are compared with estimates obtained by measuring the incident beam energy threshold for secondary electron emission and the temperature dependence positronium(Ps) emission. The experiments provide strong evidence for the existence of a positron bound state at the surface of Bi2Te2Se and indicate the practicality of using positron annihilation to selectively probe the critically important top most layer of topological insulator system.

[发布机构] Physics Department, University of Texas at Arlington, Arlington; TX; 76019-0059, United States^1;Physics Department, Northeastern University, Boston; MA; 02115, United States^2

[效力级别] 化学

[关键词] Auger electron spectrometers;Auger emission;Energy spectra;Incident beam energy;Secondary electron emissions;Surface bounds;Temperature dependence;Topological insulators