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2020/01 Lifshitz Semimetal – Semiconductor Transition in 2D PtTe2 via Film Thickness Control

Lifshitz Semimetal – Semiconductor Transition in 2D PtTe2 via Film Thickness Control        Focus ImageDr. Meng-Kai Lin(left), Dr. Tai-Chang Chiang(middle), Dr. Feng-Chuan Chuang(right)

Lifshitz Semimetal – Semiconductor Transition in 2D PtTe2 via Film Thickness Control
by National Sun Yat-sen University

Their research focused mainly on the changes in the physical properties of the different number of layers of ultrathin PtTe2 films, from one to a few layers. It was revealed that 2D PtTe2 with thicknesses from 1 tri-atomic layer (TL) to 5 TL provides clear evidence that the semimetal-to-semiconductor transition does occur when the film thickness of PtTe2 is reduced to a single TL. The gap for the single TL is quite large (0.79 eV based on theory), and thus the change in the electronic property represents an unusually strong Lifshitz transition. Moreover, detailed layer-resolved band mapping results showed the very large modifications in the electronic structure, including gap opening across the transition. The small electron pockets that appear at film thicknesses larger than 1 TL suggest that these PtTe2 films are good candidates for exhibiting an excitonic insulator phase. With these findings, a novel film-thickness-mediated Lifshitz electronic transition at the two-dimensional, single-layer limit is established. 

Figure4_hires (a) ARPES maps taken under different thicknesses along the Γ – K direction. (b) Corresponding 2nd derivative of the ARPES intensity. (c) Calculated band structures. (d) Superimpos

This collaborative team applied the density functional theory and the angle-resolved photoemission spectroscopy method, which allowed them to be able to clearly study the electronic structure of two-dimensional materials. Their research could be of a great help for investigating the basic properties, as well as the possible applications of the said material in the future.

Prof. Chuang’s team included Dr. Chia-Hsiu Hsu and Ph. D. student Rovi Angelo B. Villaos from the Philippines, while the other side of Prof. Chiang’s team consisted of Dr. Meng-Kai Lin and Ph.D. Student Joseph A. Hlevyack.

(from left to right) Dr. Chia-Hsiu Hsu, Dr. Feng-Chuan Chuang, Ph. D. student Rovi Angelo B. Villaos

Professor Chuang said the joint international team not only fosters bilateral exchange but also helps students understand the focal research points of the leading teams of different fields. In the future, they hope to expand their ties to collaborate with more laboratory teams domestically and globally with the aim of increasing their international academic reputation.


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