Structure and electronic properties of single layer transition metal chalcogenides prepared by interface reactions with Bi2Se3

Synopsis

Transition metal chalcogenides represent an important class of materials owing to their fascinating properties as superconductors, charge density wave (CDW) materials or as candidates of new topological systems like Weyl semimetals. 
For instance, bulk iron selenide (α-FeSe) belongs to the group of pnictide superconductors and among them has the most simple structure with a bulk transition temperature of TC=8 K. On the other hand, TaSe2 and MoTe2 are known as prototype materials of a CDW material and as a candidate of a Weyl semimetal. Up to now, most investigations have concentrated on bulk samples and reduction of the sample size to the ultra-thin film limit is expected to involve new phenomena due to symmetry lowering and hybridization with the substrate on which the films are grown. 

In this talk I will discuss the preparation and the analysis of FeSe, TaSe2 and MoTe2 single (tri-) layer films grown by an interface reaction of the corresponding metals with Bi2Se3(0001) and Bi2Te3(0001) single crystal surfaces respectively. This new preparation method has proven to yield high quality films as evidenced by surface x-ray diffraction, x-ray absorption fine structure and scanning tunnelling microscopy experiments. Simultaneously, the electronic structure was investigated by (spin-polarized) angular photoemission spectroscopy and scanning tunnelling spectroscopy providing surprising results such as a strong enhancement of the superconducting gap in FeSe or the appearance of spin polarized states in the case of TaSe2 and MoSe2.