Majorana fermion (MF) whose antiparticle is itself has been predicted in condensed matter systems. Signatures of the MFs have been reported as zero energy modes in various systems. More definitive evidences associated with MF's novel properties are highly desired to verify the existence of the MF. Very recently, theory has predicted MFs to induce spin selective Andreev reflection (SSAR), a novel magnetic property which can be used to detect the MFs. Here we report the first observation of the SSAR from MFs inside vortices in Bi 2 Te 3 /NbSe 2 hetero-structure, in which topological superconductivity was previously established. By using spin-polarized scanning tunneling

Kagome superconductors with T C up to 7 K have been discovered for over 40 y. Recently, unconventional chiral charge order has been reported in kagome superconductor KV 3 Sb 5 , with an ordering temperature of one order of magnitude higher than the T C . However, the chirality of the charge order has not been reported in the cousin kagome superconductor CsV 3 Sb 5 , and the electronic nature of the chirality remains elusive. In this paper, we report the observation of electronic chiral charge order in CsV 3 Sb 5 via scanning tunneling microscopy (STM). We observe a 2 × 2 charge modulation and a 1 × 4 superlattice in both topographic data and tunneling spectroscopy. 2 × 2 charge modulation is highly anticipated as a charge order by fundamental kagome lattice models at van Hove filling, and is shown to exhibit intrinsic chirality. We find that the 1 × 4 superlattices form various small domain walls, and can be a surface effect as supported by our first-principles calculations. Crucially, we find that the amplitude of the energy gap opened by the charge order exhibits real-space modulations, and features 2 × 2 wave vectors with chirality, highlighting the electronic nature of the chiral charge order. STM study at 0.4 K reveals a superconducting energy gap with a gap size 2 = 0.85 meV, which estimates a moderate superconductivity coupling strength with 2 /k B T C = 3.9. When further applying a c-axis magnetic field, vortex core bound states are observed within this gap, indicative of clean-limit superconductivity.

Ultrathin freestanding bismuth film is theoretically predicted to be one kind of two-dimensional topological insulators. Experimentally, the topological nature of bismuth strongly depends on the situations of the Bi films. Film thickness and interaction with the substrate often change the topological properties of Bi films. Using angle-resolved photoemission spectroscopy, scanning tunneling microscopy or spectroscopy and first-principle calculation, the properties of Bi(111) ultrathin film grown on the NbSe superconducting substrate have been studied. We find the band structures of the ultrathin film is quasi-freestanding, and one-dimensional edge state exists on Bi(111) film as thin as three bilayers. Superconductivity is also detected on different layers of the film and the pairing potential exhibits an exponential decay with the layer thicknesses. Thus, the topological edge state can coexist with superconductivity, which makes the system a promising platform for exploring Majorana Fermions.

Transition-metal dichalcogenides (TMDs) with the common formula MX 2 (M = Mo, W; X=S, Se, Te) exist in different phases such as the hexagonal (2H), octahedral (1T), monoclinic (1T') and orthorhombic (Td) structures. [1,2,[3][4][5][6][7] The 2H phase is most common including, for example, metal disulfides (MS 2 ) and diselenides (MSe 2 ), which are direct gap semiconductors for monolayer (ML) thin films. [1,8] They have attracted extensive research attention in recent years due to their appeals in microelectronic, optoelectronic, spin and valley electronic applications. [1,9,10,11,12] The 1T' or Td phase MX 2 are of the distorted 1T structure, which usually show semi-metallic behavior. [3,[13][14][15] Examples of the latter include WTe 2 and -MoTe 2 , which have drawn special interests lately following some recent revelations of, e.g., the large and unsaturated magnetoresistance, [4,15,16,17,18] pressure-driven superconductivity, [7,19] novel optical properties and characteristics, [11,12,17,18,20] and the topological insulator [14] and Weyl semimetal states. [6,7,21] Metallic TMDs are also good catalysts for hydrodesulfurization and hydrogen evolution reactions. [22] The large difference in electrical properties between 2H and 1T' (Td) phases of MX 2 further makes them promising for phase-change electronics. [23,24] Therefore, tuning and stabilizing the different phases of MX 2 can be of great scientific and application relevance.Among the various TMDs, MoTe 2 takes a special place as there is a small energy difference between its 2H and 1T' phases (~ 43meV per formula unit [5] ). The hexagonal phase of MoTe 2 is slightly more stable than 1T' MoTe 2 under ambient conditions, while the latter becomes more favorable at high temperature and/or under 3 tensile strain. [5,24] In any case, due to the small energy difference between the two structures, there is a high chance for one to obtain samples containing coexisting phases or to purposely tune the structure of MoTe 2 crystal by applying external constraints. This would lead to many new applications of the TMD thin films. [18] In this work, we report growths of both 2H and 1T' MoTe 2 ML by molecular beam epitaxy (MBE). We reveal a dramatic effect of Te adsorption on 1T' phase MoTe 2 formation and growth. By changing the conditions of MBE and by annealing, we can achieve effective tuning of the structural phase of MoTe 2 . Employing scanning tunneling microscopy and spectroscopy (STM/S), we establish unambiguously the structures and electronic characteristics of 2H and 1T' MoTe 2 ML such as the energy bandgap and the density of states (DOS). By consulting with the first principles calculations, we provide an explanation for the stabilization of the otherwise metastable 1T' phase MoTe 2 at the temperature and pressure condition, which is associated with Te adsorption on surface. Figure 2d. From the experimental STS data, we further derive an electronic energy gap of ~ 1.4 eV (refer to Supplementary), a value that is in qualitative agreement with that reported in li...