Experimental observation of Dirac-like surface states and topological   phase transition in Pb$_{1-x}$Sn$_x$Te(111) films
  The surface of a topological crystalline insulator (TCI) carries an even number of Dirac cones protected by crystalline symmetry. We epitaxially grew high quality Pb$_{1-x}$Sn$_x$Te(111) films and investigated the TCI phase by in-situ angle-resolved photoemission spectroscopy. Pb$_{1-x}$Sn$_x$Te(111) films undergo a topological phase transition from trivial insulator to TCI via increasing the Sn/Pb ratio, accompanied by a crossover from n-type to p-type doping. In addition, a hybridization gap is opened in the surface states when the thickness of film is reduced to the two-dimensional limit. The work demonstrates an approach to manipulating the topological properties of TCI, which is of importance for future fundamental research and applications based on TCI. 
Chenhui Yan and Junwei Liu and Yunyi Zang and Jianfeng Wang and Zhenyu   Wang and Peng Wang and Zhi-Dong Zhang and Lili Wang...
cond-mat.mtrl-sci