No abstract

The nonsymmorphic Zr 2 Ir alloy is a possible topological semimetal candidate material and as such may be part of an exotic class of superconductors. Zr 2 Ir is a superconductor with a transition temperature of 7.4 K with critical fields of 19.6(3) mT and 3.79(3) T, as determined by heat capacity and magnetization. Zero-field muon spin relaxation measurements show that time-reversal symmetry is preserved in these materials. The specific heat and transverse field muon spin rotation measurements rule out any possibility to have a nodal or anisotropic superconducting gap, revealing a conventional s-wave nature in the superconducting ground state. Therefore this system is found to be a conventional nonsymmorphic superconductor, with time-reversal symmetry being preserved and an isotropic superconducting gap.

This work presents the emergence of superconductivity in Ir - doped Weyl semimetal T$_d$ - MoTe$_{2}$ with broken inversion symmetry. Chiral anomaly induced planar Hall effect and anisotropic magneto-resistance confirm the topological semimetallic nature of Mo$_{1-x}$Ir$_{x}$Te$_{2}$. Observation of weak anisotropic, moderately coupled type-II superconductivity in T$_d$ -Mo$_{1-x}$Ir$_{x}$Te$_{2}$ makes it a promising candidate for topological superconductor.

Geometrical frustration leads to novel quantum phenomena such as the spin-liquid phase in triangular and kagome lattices. Intraband and interband Fermi surface (FS) nesting can drive unique superconducting (SC) ground states with d-wave and s ± -pairing symmetries, respectively, according to the criterion that the SC gap changes sign across the nesting wave vector. For an odd number of FSs, when multiple interband nesting is of comparable strength, the sign-reversal criterion between different FS sheets can lead to frustration, which promotes novel SC order parameters. Here, we report the experimental observation of a time-reversal symmetry breaking pairing state in Re 2 Hf resulting from FS nesting frustration. Furthermore, our electronic specific heat and transverse-field muon spin rotation experiments suggest a fully gapped pairing symmetry. The first-principles electronic structure calculation reveals multiple Fermi surface sheets with comparable interband nesting strength. Implementing the ab initio band structure, we compute spin-fluctuation mediated SC pairing symmetry which reveals an s + is -pairing state-consistent with experimental observations. Our investigation demonstrates an alternative SC state which provides a putative setting for both applied and fundamental study.

We have investigated the superconducting properties in a single crystal of a new superconductor Pb2Pd via various techniques including magnetization, AC transport, transverse field muon spin rotation and relaxation (TF-µSR), and heat capacity. Pb2Pd crystallizes in a body-centred tetragonal structure with space group I4/mcm. All measurements confirm the superconducting transition temperature, TC = 3.0 ± 0.1 K. Electronic specific heat data are well described by the BCS fitting, suggesting that Pb2Pd opens an isotropic gap on entering the superconducting state. The specific heat jump and λ e−ph value categorize Pb2Pd as a moderately coupled superconductor. Magnetization and transverse field muon spin rotation measurements along with Ginzburg-Landau parameter, κ < 1/ √ 2 strongly infers that Pb2Pd is a type I superconductor.