Recently, theory has predicted a Majorana zero mode (MZM) to induce spin selective Andreev reflection (SSAR), a novel magnetic property which can be used to detect the MZM. Here, spin-polarized scanning tunneling microscopy or spectroscopy has been applied to probe SSAR of MZMs in a topological superconductor of the ${\mathrm{Bi}}_2{\mathrm{Te}}_3/{\mathrm{NbSe}}_2$ heterostructure. The zero-bias peak of the tunneling differential conductance at the vortex center is observed substantially higher when the tip polarization and the external magnetic field are parallel rather than antiparallel to each other. This spin dependent tunneling effect provides direct evidence of MZM and reveals its magnetic property in addition to the zero energy modes. Our work will stimulate MZM research on these novel physical properties and, hence, is a step towards experimental study of their statistics and application in quantum computing.

We report an atomic-scale characterization of ${\mathrm{ZrTe}}_5$ by using scanning tunneling microscopy. We observe a bulk band gap of $\sim 80\mathrm{meV}$ with topological edge states at the step edge and, thus, demonstrate that ${\mathrm{ZrTe}}_5$ is a two-dimensional topological insulator. We also find that an applied magnetic field induces an energetic splitting of the topological edge states, which can be attributed to a strong link between the topological edge states and bulk topology. The relatively large band gap makes ${\mathrm{ZrTe}}_5$ a potential candidate for future fundamental studies and device applications.

Stop or Go on Oxide Surfaces: Direct studies of surface diffusion with instruments such as the scanning tunneling microscope (STM) have often focused on species on metal surfaces, but surface diffusion can play an important role for reactions on metal oxide surfaces. Li et al. (p. 882 ) used STM and density functional theory calculations to study how catechol (a benzene ring bearing two −OH groups) diffuses on the surface of the rutile phase of titanium dioxide. Both mobile and immobile species were observed on the time scale of minutes while making repeated STM scans. Hydrogen atom transfers between surface OH groups and the molecule changed the interaction energy between the molecule and the surface, and hence the barrier for diffusion.

We have grown nearly freestanding single-layer $1T^{\prime }-\mathrm{WT}{\mathrm{e}}_2$ on graphitized $6H$-SiC(0001) by using molecular beam epitaxy (MBE), and characterized its electronic structure with scanning tunneling microscopy/spectroscopy (STM/STS). The existence of topological edge states at the periphery of single-layer $\mathrm{WT}{\mathrm{e}}_2$ islands was confirmed. Surprisingly, a bulk band gap at the Fermi level and insulating behaviors were also found in single-layer $\mathrm{WT}{\mathrm{e}}_2$ at low temperature, which are likely associated with an incommensurate charge order transition. The realization of two-dimensional topological insulators (2D TIs) in single-layer transition-metal dichalcogenide provides a promising platform for further exploration of the 2D TIs’ physics and related applications.