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Abstract

A first-order-like resistivity hysteresis is induced by a subtle structural transition under hydrostatic pressure in the topological nodal-line superconductor PbTaSe2. This structure transition is quickly suppressed to zero at pressure similar to 0.25 GPa. As a result, superconductivity shows a marked suppression, accompanied with pronounced changes in the magnetoresistance and Hall resistivity. The first-principles calculations show that the spin-orbit interactions partially gap out the Dirac nodal line around K point in the bulk Brillouin zone upon applying a small pressure, whereas the Dirac states around H point are completely destroyed. The calculations further reveal a second structural phase transition under a pressure as high as similar to 30 GPa, through which a transition from a topologically nontrivial bulk phase to a trivial phase is uncovered, with a superconducting dome emerging under this high-pressure phase. Our calculations also reveal how the bulk Fermi surfaces and the surface bands evolve with pressure. This theoretical study shall inspire in-depth experimental investigations on the electronic structure of this novel topological superconductor under higher pressures.