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Abstract: The exploration of intriguing topological quantum physics in stanene has attracted enormous interest but is challenged by lacking desirable material samples. The successful fabrication of monolayer stanene on PbTe(111) films with low‐temperature molecular beam epitaxy and thorough characterizations of its atomic and electronic structures are reported here. In situ angle‐resolved photoemission spectroscopy together with first‐principles calculations identify two hole bands of p xy orbital with a spin‐orbit coupling induced band splitting and meanwhile reveal an automatic passivation of p z orbital of stanene. Importantly, material properties are tuned by substrate engineering, realizing a decorated stanene sample with truly insulating bulk on Sr‐doped PbTe. This finding paves a road for studies of stanene‐based topological quantum effects and electronics. [ABSTRACT FROM AUTHOR]

Recent experiments on FeSe films grown on SrTiO3 (STO) suggest that interface effects can be used as a means to reach superconducting critical temperatures (Tc) of up to 80 K (ref. ). This is nearly ten times the Tc of bulk FeSe and higher than the record value of 56 K for known bulk Fe-based superconductors. Together with recent studies of superconductivity at oxide heterostructure interfaces, these results rekindle the long-standing idea that electron pairing at interfaces between two different materials can be tailored to achieve high-temperature superconductivity. Subsequent angle-resolved photoemission spectroscopy measurements of the FeSe/STO system revealed an electronic structure distinct from bulk FeSe (refs , ), with an energy gap vanishing at around 65 K. However, ex situ electrical transport measurements have so far detected zero resistance-the key experimental signature of superconductivity-only below 30 K. Here, we report the observation of superconductivity with Tc above 100 K in the FeSe/STO system by means of in situ four-point probe electrical transport measurements. This finding confirms FeSe/STO as an ideal material for studying high-Tc superconductivity. [ABSTRACT FROM AUTHOR]

Abstract: We present the growth of atomically flat topological crystalline insulator (TCI) SnTe films on Si(111) substrate by molecular beam epitaxy (MBE). The growth condition for achieving high quality SnTe film was established by a combination of reflection high energy electron diffraction (RHEED) and scanning tunneling microscopy (STM) studies. In-situ angle resolved photoemission spectroscopy (ARPES) measurements elucidate the topological nature of the SnTe films. The electronic structure of SnTe films can be tuned by film thickness and Pb doping. The success in growing high quality SnTe thin films with tunable electronic structure is crucial for potential device applications. [Copyright &y& Elsevier]

Abstract: The electronic structure of reconstructed surface is measured by angle-resolved photoemission spectroscopy. By the first time, band splitting at and points in the surface Brillouin zone (SBZ) of this system is observed, which could be simply interpreted in the framework of Rashba splitting. Furthermore, first principle calculation is carried out and compared with our experimental results. [Copyright &y& Elsevier]

The newly discovered alkali-doped iron selenide superconductors not only reach a superconducting transition temperature as high as 32?K, but also exhibit unique characteristics that are absent from other iron-based superconductors, such as antiferromagnetically ordered insulating phases, extremely high Néel transition temperatures and the presence of Fe vacancies and ordering. These features have generated considerable excitement as well as confusion, regarding the delicate interplay between Fe vacancies, magnetism and superconductivity. Here we report on molecular beam epitaxy growth of high-quality KxFe2?ySe2 thin films and in situ low-temperature scanning tunnelling microscope measurement of their atomic and electronic structures. We demonstrate that a KxFe2?ySe2 sample contains two distinct phases: an insulating phase with well-defined order of Fe vacancies, and a superconducting KFe2Se2 phase containing no Fe vacancies. An individual Fe vacancy can locally destroy superconductivity in a similar way to a magnetic impurity in conventional superconductors. Measurement of the magnetic-field dependence of the Fe-vacancy-induced bound states reveals a magnetically related bipartite order in the tetragonal iron lattice. These findings elucidate the existing controversies on this new superconductor and provide atomistic information on the interplay between magnetism and superconductivity in iron-based superconductors. [ABSTRACT FROM AUTHOR]

We perform molecular beam epitaxy growth and scanning tunneling microscopy study of copper diselenide (CuSe2) films on SrTiO3(001). Using a Se-rich condition, the single-phase pyrite CuSe2 grows in the Stranski—Krastanov (layer-plus-island) mode with a preferential orientation of (111). Our careful inspection of both the as-grown and post-annealed CuSe2 films at various temperatures invariably shows a Cu-terminated surface, which, depending on the annealing temperature, reconstructs into two distinct structures and . The Cu termination is supported by the depressed density of states near the Fermi level, measured by in-situ low temperature scanning tunneling spectroscopy. Our study helps understand the preparation and surface chemistry of transition metal pyrite dichalcogenides thin films. [ABSTRACT FROM AUTHOR]