Jiaqi Guan

Detection of a superconducting phase in a two-atom layer of hexagonal Ga film grown on semiconducting GaN(0001).

The recent observation of the superconducting state at atomic scale has motivated the pursuit of exotic condensed phases in two-dimensional (2D) systems. Here we report on a superconducting phase in two-monolayer crystalline Ga films epitaxially grown on wide-band-gap semiconductor GaN(0001). This phase exhibits a hexagonal structure and only 0.552 nm in thickness, nevertheless, brings about a superconducting transition temperature Tc as high as 5.4 K, confirmed by in situ scanning tunneling spectroscopy and ex situ electrical magnetotransport and magnetization measurements. The anisotropy of critical magnetic field and Berezinski-Kosterlitz-Thouless-like transition are observed, typical for the 2D superconductivity. Our results demonstrate a novel platform for exploring atomic-scale 2D superconductors, with great potential for understanding the interface superconductivity.

Molecular beam epitaxy growth and scanning tunneling microscopy study of TiSe

Molecular beam epitaxy is used to grow TiSe2 ultrathin films on graphitized SiC(0001) substrate. TiSe2films proceed via a nearly layer-by-layer growth mode and exhibit two dominant types of defects, identified as Se vacancy and interstitial, respectively. By means of scanning tunneling microscopy, we demonstrate that the well-established charge density waves can survive in single unit-cell (one triple layer) regime, and find a gradual reduction in their correlation length as the density of surface defects in TiSe2 ultrathin films increases. Our findings offer important insights into the nature of charge density wave in TiSe2, and also pave a material foundation for potential applications based on the collective electronic states.

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Tellurium (Te) films with monolayer and few-layer thickness are obtained by molecular beam epitaxy on a graphene/6H-SiC(0001) substrate and investigated by in situ scanning tunneling microscopy and spectroscopy (STM/STS). We reveal that the Te films are composed of parallel-arranged helical Te chains flat-lying on the graphene surface, exposing the (1 × 1) facet of (101̅0) of the bulk crystal. The band gap of Te films increases monotonically with decreasing thickness, reaching the near-infrared band for the monolayer Te. An explicit band bending at the edge between the monolayer Te and graphene substrate is visualized. With the thickness controlled in the atomic scale, Te films show potential applications of electronics and optoelectronics.

ultrathin films

The significant role of interfacial coupling in the enhancement of superconductivity in FeSe films on

Epitaxial Growth and Band Structure of Te Film on Graphene

{\mathrm{SrTiO}}_{3}

Role of SrTiO 3 phonon penetrating into thin FeSe films in the enhancement of superconductivity

has been widely recognized, but the explicit origin of this coupling is yet to be identified. Here, by surface phonon measurements using high-resolution electron energy loss spectroscopy, we found the electric field generated by Fuchs-Kliewer (F-K) phonon modes of

Visualizing the elongated vortices in γ-Ga nanostrips

{\mathrm{SrTiO}}_{3}

Lattice dynamics of ultrathin FeSe films on SrTiO 3

can penetrate into FeSe films and strongly interact with the electrons therein. The mode-specific electron-phonon coupling constant for the

Superconducting transition of FeSe / SrTiO3 induced by adsorption of semiconducting organic molecules

\ensuremath{\sim}92

Realization of In‐Plane p–n Junctions with Continuous Lattice of a Homogeneous Material

meV F-K phonon is