Here we report the evidence of the type-II Dirac Fermion in the layered crystal PdTe 2. The de Haas-van Alphen oscillations find a small Fermi pocket with a cross section of 0.077nm -2 with a nontrivial Berry phase. First-principal calculations reveal that it is originated from the hole pocket of a tilted Dirac cone. Angle Resolved Photoemission Spectroscopy demonstrates a type-II Dirac cone featured dispersion.We also suggest PdTe 2 is an improved platform to host the topological superconductors.

ZrSiS materials show unsaturated magnetoresistance until a magnetic field of 53 T with a butterfly‐shaped angular dependence. Intense Shubnikov‐de Haas oscillations resolve a bulk Dirac cone with a nontrivial Berry phase. Combined with angle‐resolved photoemission spectroscopy and theoretical calculations, ZrSiS is proved to be a Dirac material with both surface and bulk Dirac bands.

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The promising n-Si-based solar cell is constructed for the purpose of realizing hole- and electron-selective passivating contact, using a textured front indium tin oxide/MoO structure and a planar rear a-SiO/poly(Si(n)) structure severally. The simple MoO /n-Si heterojunction device obtains an efficiency of 16.7%. It is found that the accompanying ternary hybrid SiO(Mo) interlayer (3.5-4.0 nm) is formed at the MoO /n-Si boundary zone without preoxidation and is of amorphous structure, which is determined by a high-resolution transmission electron microscope with energy-dispersive X-ray spectroscopy mapping. The creation of lower-oxidation states in MoO film indicates that the gradient distribution of SiO with Mo element occurs within the interlayer, acting as a passivation of silicon substrate, which is revealed by X-ray photoelectron spectroscopy with depth etching. Specifically, calculations by density functional theory manifest that there are two half-filled levels (localized states) and three unoccupied levels (extended states) relating to Mo component in the ternary hybrid a-SiO(Mo) interlayer, which play the roles of defect-assisted tunneling and direct tunneling for photogenerated holes, respectively. The transport process of photogenerated holes in the MoO /n-Si heterojunction device is well-described by the tunnel-recombination model. Meanwhile, the a-SiO/poly(Si(n)) has been assembled on the rear of the device for direct tunneling of photoinduced electrons and blocking photoinduced holes.

Quantum interference effects (QIEs) dominate the appearance of low-temperature resistivity minimum in colossal magnetoresistance manganites. The T1/2 dependent resistivity under high magnetic field has been evidenced as electron-electron (e-e) interaction. However, the evidence of the other source of QIEs, weak localization (WL), still remains insufficient in manganites. Here we report on the direct experimental evidence of WL in QIEs observed in the single-crystal La0.7Sr0.3MnO3 (LSMO) ultrathin films deposited by laser molecular beam epitaxy. The sharp cusps around zero magnetic field in magnetoresistance measurements is unambiguously observed, which corresponds to the WL effect. This convincingly leads to the solid conclusion that the resistivity minima at low temperatures in single-crystal manganites are attributed to both the e-e interaction and the WL effect. Moreover, the temperature-dependent phase-coherence length corroborates the WL effect of LSMO ultrathin films is within a two-dimensional localization theory.

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High-mobility (Smx Bi1-x )2 Se3 topological insulators (with x = 0.05) show a Curie temperature of about 52 K, and the carrier concentration and Fermi wave vector can be manipulated by intentional Te introduction with no significant influence on the Curie temperature. The origin of the ferromagnetism is attributed to the trivalent Sm dopant, as confirmed by X-ray magnetic circular dichroism and first-principles calculations. The carrier concentration is on the order of 10(19) cm(-3) and the mobility can reach about 7200 cm(2) V(-1) s(-1) with pronounced Shubnikov-de Haas oscillations.

We report on an avenue to obtain the centimeter-scale, uniform, and high-quality WTe2 ultrathin films by a pulsed laser deposition technique and the post-annealing under the tellurium (Te) vapor. The WTe2 ultrathin films showed the typical metallic behavior when Te vacancies were mostly eliminated. Magnetoresistance measurements showed that WTe2 ultrathin films underwent the competition between weak localization and weak antilocalization that could be modulated by the amount of Te vacancies. Our study may open an avenue to improve the charge transport of WTe2 for its two-dimensional device applications.