| AVS 63rd International Symposium & Exhibition | |
| 2D Materials Focus Topic | Tuesday Sessions |
| Session 2D+MI-TuM |
| Session: | Novel 2D Materials |
| Presenter: | Charlotte Sanders, Aarhus University, Denmark |
| Authors: | C.E. Sanders, Aarhus University, Denmark M. Dendzik, Aarhus University, Denmark A.S. Ngankeu, Aarhus University A. Eich, Radboud University, Netherlands A. Bruix, Aarhus University, Denmark J.A. Miwa, Aarhus University, Denmark B. Hammer, Aarhus University, Denmark A.A. Khajetoorians, Radboud University, Netherlands P. Hofmann, Aarhus University, Denmark |
| Correspondent: | Click to Email |
The electronic properties of bulk TaS2 have long been a topic of significant interest, due to the fact that the material exhibits unusual charge density wave phases alongside Mott physics and superconductivity. However, little has been known about single-layer (SL) TaS2. How the electronic properties of this material may change in the SL limit is of great interest, raising questions about the effects of quantum confinement and substrate interactions on exotic electronic states already seen in the bulk. Work on related materials that have been successfully fabricated as SLs points to complex consequences for the CDW and superconducting states. [1] In order to address this topic, one needs to be able to controllably fabricate high-quality, uniform samples with low defect densities for probing in situ. We have now succeeded in epitaxially growing high-quality SL TaS2. We have characterized the SL with angle-resolved photoemission spectroscopy (ARPES), low-temperature scanning tunneling microscopy and spectroscopy (LT-STM/S), and low-energy electron diffraction (LEED). Using the Au(111) substrate as a starting point, we find that the TaS2 SL on Au(111) assumes a well-defined orientation with respect to the substrate, and a moiré superstructure; simultaneously, and counterintuitively, it adopts a “carpet flow” growth mode over substrate steps, suggesting weak interaction with the substrate. Comparing our measurements to calculations from density functional theory (DFT), we have determined that the SL assumes the trigonal prismatic (“1H”) phase. While the bulk parent material is characterized by a CDW transition temperature TCDW = 75K [2], we do not observe either CDWs or superconductivity at temperatures down to 4.7K on Au(111) using STM/STS. We do, however, observe slight doping of the TaS2 epilayer. While the absence of superconductivity at this temperature is not surprising, considering that the superconducting transition temperature TC in the bulk is only 600mK [3], the absence of CDWs is of interest. This is particularly so in light of recent research on the closely related system SL-NbSe2 on bilayer graphene: despite having a lower bulk CDW onset at TCDW = 33K, NbSe2 in the SL exhibits complete transition to the CDW state by TCDW = 5K. [1]
[1] M. M. Ugeda et al., Nat. Phys.12, 92 (2016). http://dx.doi.org/10.1038/nphys3527
[2] J. A. Wilson and A. Yoffe, Adv. Phys.18, 193 (1969). http://dx.doi.org/10.1080/00018736900101307
[3] P. Garoche et al., J. Low Temp. Phys.30, 323 (1978). http://dx.doi.org/10.1007/BF00114956