Non-centrosymmetric Superconductor PbTaSe₂ Under Pressure And Enhanced Electron Correlations PdSn₄

First section:Studying superconductor is an important field in condensed matter physics from first superconductor found.The scientists performed the ma-terials according to their magnetic properties,critical temperature,phase transi-tion process,interaction in order to find their superconductivity mechanism.One kind of superconductor whose crystalline structure does't contain space-reversal-invariant center.This kind of superconductor was called to be non-centrosymmetric superconductor which correlated with unusual physic properties usually.Antisymmetric spin-orbital coupling effect lead to superconductivity electronic pairs is not only spin singlet pairing,but also spin triplet pairing in non-centrosymmetric super-conductor.Recently,theoreticla demonstration indicated P bT aSe₂is strong spin-orbital coupling and topological nodal line superconductor.We study its detailed properties under different pressures.We find resistivity hysteresis under about0.25GPa at 280K.So we study its magnetoresistance and hall resistivity under different pressures.The first-principles calculations show that the spin-orbit in-terctions partially gap out the Dirac nodal line around K point in the bulk Bril-louin zone upon applying a small pressure about 5GPa,whereas the Dirac states around H point are completely destroyed.The calculations further reveal a second structural phase transition from hexagonal to tetragonal around 30GPa.We also calculated how the bulk Fermi surfaces and the surface bands evolve with pres-sure and how the electron-phonon coupling constant,critical temperature evolve with pressure.Our calculation show this structure above 30GPa is also a su-perconductivity phase.This theoretical study shall inspire in-depth experimental investigations on the electronic structure of this novel topological superconductor under high pressure.Second section:The quest for quantum materials with diverse symmetrypro-tected topological states has been a major driver of the field of condensed-matter physics in recent years.Due to the advent of Dirac/Weyl semimetals?WSMs?,the research interest in topological phenomena now encompasses topological insulators?TIs?and semimetals.Three-dimensional topological Dirac or Weyl semimetals are new states of matter that possess a linear band dispersion in the bulk along all threemomentum directions,whose low-energy quasiparticles are the condensed-matter analogues of Dirac and Weyl fermions in relativistic high-energy physics.Many exotic transport behaviors associated with these topological states,such as the chiral anomaly and large linear magnetoresistance?LMR?,were identified experimentally soon after their discovery.In this section,wo report shythesis?resistivity?hall resistivity?susceptibility?angle magenetoresistance?dHvA os-cillation about a new topological nodal line semimetal PdSn₄which simlar to PtSn₄...