arXiv subjects

Chao-Long Yang

Publications and source records attributed to Chao-Long Yang.

4 recordsLinked to original sources

arXiv2018

Unveiling the Charge Density Wave Inhomogeneity and Pseudogap State in 1T-TiSe2

By using scanning tunneling microscopy (STM) / spectroscopy (STS), we systematically characterize the electronic structure of lightly doped 1T-TiSe2, and demonstrate the existence of the electronic inhomogeneity and the pseudogap state. It is found that the intercalation induced lattice distortion impacts the local band structure and reduce the size of the charge density wave (CDW) gap with the persisted 2x2 spatial modulation. On the other hand, the delocalized doping electrons promote the formation of pseudogap. Domination by either of the two effects results in the separation of two characteristic regions in real space, exhibiting rather different electronic structures. Further doping electrons to the surface confirms that the pseudogap may be the precursor for the superconducting gap. This study suggests that the competition of local lattice distortion and the delocalized doping effect contribute to the complicated relationship between charge density wave and superconductivity for intercalated 1T-TiSe2.

cond-mat.str-el↗

arXiv2016

Tailoring Kinetics on a Topological Insulator Surface by Defect-Induced Strain: Pb Mobility on Bi2Te3

Heteroepitaxial structures based on Bi$_{2}$Te$_{3}$-type topological insulators (TIs) exhibit exotic quantum phenomena. For optimal characterization of these phenomena, it is desirable to control the interface structure during film growth on such TIs. In this process, adatom mobility is a key factor. We demonstrate that Pb mobility on the Bi$_{2}$Te$_{3}$(111) surface can be modified by the engineering local strain, ε, which is induced around the point-like defects intrinsically forming in the Bi$_{2}$Te$_{3}$(111) thin film grown on a Si(111)-7 $\times$ 7 substrate. Scanning tunneling microscopy observations of Pb adatom and cluster distributions and first-principles density functional theory (DFT) analyses of the adsorption energy and diffusion barrier E$_{d}$ of Pb adatom on Bi$_{2}$Te$_{3}$(111) surface show a significant influence of ε. Surprisingly, E$_d$ reveals a cusp-like dependence on ε due to a bifurcation in the position of the stable adsorption site at the critical tensile strain ε$_{c}$ $ \approx $ 0.8%. This constitutes a very different strain-dependence of diffusivity from all previous studies focusing on conventional metal or semiconductor surfaces. Kinetic Monte Carlo simulations of Pb deposition, diffusion, and irreversible aggregation incorporating the DFT results reveal adatom and cluster distributions compatible with our experimental observations.

cond-mat.mtrl-sci↗

arXiv2016

Real-space characterization of reactivity towards water at Bi2Te3(111) surface

Surface reactivity is important in modifying the physical and chemical properties of surface sensitive materials, such as the topological insulators (TIs). Even though many studies addressing the reactivity of TIs towards external gases have been reported, it is still under heavy debate whether and how the topological insulators react with H$_2$O. Here, we employ scanning tunneling microscopy (STM) to directly probe the surface reaction of Bi$_2$Te$_3$ towards H$_2$O. Surprisingly, it is found that only the top quintuple layer is reactive to H$_2$O, resulting in a hydrated Bi bilayer as well as some Bi islands, which passivate the surface and prevent from the subsequent reaction. A reaction mechanism is proposed with H$_2$Te and hydrated Bi as the products. Unexpectedly, our study indicates the reaction with water is intrinsic and not dependent on any surface defects. Since water inevitably exists, these findings provide key information when considering the reactions of Bi$_2$Te$_3$ with residual gases or atmosphere.

cond-mat.mtrl-sci↗

arXiv2016

Robust topological edge states at the perfect surface step edge of topological insulator ZrTe$_5$

We report an atomic-scale characterization of ZrTe$_5$ by using scanning tunneling microscopy. We observe a bulk bandgap of ~80 meV with topological edge states at the step edge, and thus demonstrate ZrTe$_5$ is a two dimensional topological insulator. It is also found that an applied magnetic field induces energetic splitting and spatial separation of the topological edge states, which can be attributed to a strong link between the topological edge states and bulk topology. The perfect surface steps and relatively large bandgap make ZrTe$_5$ be a potential candidate for future fundamental studies and device applications.

cond-mat.mtrl-sci↗