Pressure-induced superconductivity and topological phase transitions in the topological nodal-line semimetal SrAs3

Abstract

Topological nodal-line semimetals (TNLSMs) are materials whose conduction and valence bands cross each other, meeting a topologically protected closed loop rather than discrete points in the Brillouin zone (BZ). The anticipated properties for TNLSMs, include drumhead-like nearly flat surface states, unique Landau energy levels, special collective modes, long-range Coulomb interactions, or the possibility of realizing high-temperature superconductivity. Recently, SrAs 3 has been theoretically proposed and then experimentally confirmed to be a TNLSM. Here, we report high-pressure experiments on SrAs 3 , identifying a Lifshitz transition below 1 GPa and a superconducting transition accompanied by a structural phase transition above 20 GPa. A topological crystalline insulator (TCI) state is revealed by means of density functional theory (DFT) calculations on the emergent high-pressure phase. As the counterpart of topological insulators, TCIs possess metallic boundary states protected by crystal symmetry, rather than time reversal. In consideration of topological surface states (TSSs) and helical spin texture observed in the high-pressure state of SrAs 3 , the superconducting state may be induced in the surface states, and is most likely topologically nontrivial, making pressurized SrAs 3 a strong candidate for topological superconductor.

The Remarkable Anisotropic Compressibility and Metallic CrCr Chains in Topological Semimetal CrP4 under High Pressure

“…Recently, there are a lot of topological materials that were experimentally and theoretically reported, [24] including the metal pnictides which have been reported to possess topological properties at ambient pressure and even under high pressure, such as TaAs 2 [25] and SrAs 3 . [16] Theoretically, CrP 4 was predicted to be a topological high-symmetry line semimetal when spinorbit coupling (SOC) was not considered very recently. [18] The electronic band calculations showed that CrP 4 is a semiconductor with an indirect bandgap of 0.47 eV according to the density functional theory calculation in the study by Khan et al [26] Instead, CrP 4 was reported to have a direct bandgap of 0.63 eV in Gong's research work.…”

“…Generally speaking, the atomic arrangements of the compounds containing light elements at higher pressures are those observed in analogous compounds with heavy elements of the same group at lower pressures, which is the so-called "corresponding static principle" rule such as Li 3 N (transforming from P6/mmm phase to P6 3 /mmc phase (which is the ambient pressure phase of Li 3 P) at 0.5 GPa, Fm-3m phase (which is the structure of Li 3 Bi at ambient pressure) at 36-45 GPa, [15] and SrAs 3 from C2/m phase to Pm-3m phase (the ambient pressure phase of SrBi 3 ) at 23.3 GPa. [16] Kinomura et al synthesized WP 4 using a cubic-type high-pressure vessel (3 GPa and 1000 C). The lattice parameters of WP 4 obtained by powder XRD were refined to obtain a body-centered tetragonal phase with a ¼ 5.702 Å and c ¼ 9.352 Å.…”

Magnetism-induced topological transition in EuAs3

“…Recently, the non-magnetic CaP 3 family of materials was proposed as potential host of topological nodal-line (TNL) semimetals 6 , among which SrAs 3 possesses a TNL feature at ambient pressure 7 – 9 and exotic properties under high pressure 10 . Isostructural with SrAs 3 , EuAs 3 orders in an incommensurate antiferromagnetic (AFM) state at T N = 11 K, and then undergoes an incommensurate–commensurate lock-in phase transition at T L = 10.3 K, producing a collinear AFM ground state 11 – 16 .…”

Fragile topology in nodal-line semimetal superconductors

“…Previously, the NLSM superconductor has been studied intensively [9,10,[34][35][36][37][38][39][40][41][42][43][44][45]. In the superconducting state, the single-band inversion naturally becomes the double band inversion due to the particle-hole symmetry.…”