The physical mechanism driving the γ – α phase transition of face-centre-cubic (fcc) cerium (Ce) remains controversial until now. In this work, high-quality single crystalline fcc–Ce thin films were grown on Graphene/6 H -SiC(0001) substrate, and explored by XRD and ARPES measurement. XRD spectra showed a clear γ – α phase transition at T γ − α ≈ 50 K, which is retarded by strain effect from substrate comparing with T γ − α (about 140 K) of the bulk Ce metal. However, APRES spectra did not show any signature of α -phase emerging in the surface-layer from 300 to 17 K, which implied that α -phase might form at the bulk-layer of our Ce thin films. Besides, an evident Kondo dip near Fermi energy was observed in the APRES spectrum at 80 K, indicting the formation of Kondo singlet states in γ –Ce. Furthermore, the DFT + DMFT calculations were performed to simulate the electronic structures and the theoretical spectral functions agreed well with the experimental ARPES spectra. In γ –Ce, the behavior of the self-energy’s imaginary part at low frequency not only confirmed that the Kondo singlet states emerged at T K S ≥ 80 K, but also implied that they became coherent states at a lower characteristic temperature ( T coh ~40 K) due to the indirect RKKY interaction among f – f electrons. Besides, T coh from the theoretical simulation was close to T γ−α from the XRD spectra. These issues suggested that the Kondo scenario might play an important role in the γ– α phase transition of cerium thin films.

Topological insulators (TIs) are theoretically believed to possess robust surface states (SSs) for any surface terminations. In reality, for TIs with non-conventional terminations, the directly experimental demonstration of this argument is somehow hindered, due to the difficulties in sample preparation and lack of efficient electronic structure characterization method. Here, by using the state-of-the-art molecular beam epitaxy, we manage to prepare TI Bi2Te3 thin film with non-conventional fractional quintuple layer (FQL) termination. Scanning tunneling microscopy reveals that the as-grown Bi2Te3 thin film may not necessarily terminate at the van der Waals gap between two adjacent quintuple layers. The electronic structures of the FQL termination are studied in combination with quasi-particle interference pattern by scanning tunneling spectroscopy and SS calculations by tight binding method. Our results suggest that the topological nature of SSs be preserved on various terminations. Possible ways of achieving exotic topological SSs are also discussed.