| The topological matter is a brand new classification of condensed matter which has stimulated widespread interest in physics.Various topological materials,such as topological insulators and topological semimetals,have been discovered to manifest exotic quasi-particle excitation and novel physical properties.These topological materials not only provide versatile experimental platforms for basic scientific research,but also pave a way for potential applications of the electronics industries and quantum computing in the future.Topological materials have achieved tremendous development in condensed matter physics and materials science during the pasted decade.Considering the fast development of this field,I think the researches on topological matters will focus on two main directions.Firstly,the physical properties will be kept investigation and diversified configuration of electronic and spintronic devices will be manufactured based on these materials,especially on Bi2Se3 family of topological insulators.Secondly,people will continue to discover new classification of topological phase and keep on the refinement and optimization of the topological material family system.The results discussed in this paper are involved in both aspects and the main three parts of the researches are as follows:(1)A lateral heterojunction of topological insulator Sb2Te3/Bi2Te3 was successfully synthesized by a two-step solvothermal method.The two crystalline components are separated well by a sharp lattice-matched interface.Both inner and outer zones hold the same thickness with 10-20 nm.Inspecting the heterojunction by high-resolution transmission electron microscopy,epitaxial growth occurs at the interface of the junction.The semiconducting temperature-dependent resistance curve and crossjunction rectification are observed,which reveal a staggered-gap with about 3 meV near the interface.Weak antilocalization in low temperature magnetoresistance reveals the well maintained transport of the topological surface states.(2)PdTe2 is a new kind of type-II Dirac semimetal in topological matters.High-quality PdTe2 single crystals were grown by the melting method.Obvious de Haas-van Alphen oscillations were observed at low temperature.Nontrivial Berry phase can be extracted from an oscillation mode with low frequency of 8 T.The First-principles calculations reveal that it is originated from the hole pocket with a cross section of 0.077 nm-2 forming by the tilted Dirac cone.Angle-resolved photoemission spectroscopy(ARPES)demonstrates the Dirac cone dispersion with type-II properties and the Dirac point is 0.53 eV lower than the Fermi level.PdTe2 is also a superconductor with Tc-1.9 K.The anisotropic superconductive properties of PdTe2 were systematically studied.(3)A new type-II Dirac semimetal in Ir1-xPtxTe2 with optimized band structures was experimentally discovered.Pt dopant protects the crystal structure of 1T phase which holds the Dirac cones and tunes the Fermi level close to Dirac point.Type-II Dirac dispersion in Ir1-xPtxTe2 is confirmed by combining ARPES with first-principle calculations.Superconductivity was also observed to persist with Tc-0.15 K when Fermi level aligns with the Dirac points for the sample of x = 0.3.Ir1-xPtxTe2 is an ideal platform for further studies on the exotic properties and potential applications of type-II DSMs,which opens up a new route to investigate the possible topological superconductivity and Majorana physics in the future. |
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