Multiband superconductivity ofTa4Pd3Te16from Tepstates

Abstract

Ta4Pd3Te16 is a recently discovered superconductor that has been suggested to be an unconventional superconductor near magnetism. We report electronic structure calculations showing that in spite of the layered crystal structure the material is an anisotropic three dimensional metal. The Fermi surface contains prominent one and two dimensional features, including nested 1D sheets, a 2D cylindrical section and a 3D sheet. The electronic states that make up the Fermi surface are mostly derived from Te p states, with small Ta d and Pd d contributions. This places the compound far from magnetic instabilities. The results are discussed in terms of multiband superconductivity.

Thermodynamic anomaly above the superconducting critical temperature in the quasi-one-dimensional superconductorTa4Pd3Te16

“…Owing to the q1D nature of TPT, it has long been speculated that a Peierls instability to charge density wave (CDW) formation may be present [6,7,12]. The best evidence for such a state comes from scanning tunneling microscopy (STM) measurements on the surface of the material, which see a clear modulation of period four in the along-chain b direction at 4 K, in one of the three chain types [19].…”

“…This may be because TPT is significantly more isotropic: although direct resistivity measurements have been unavailable until now, measurements of the upper critical field have given indirect evidence that the electronic anisotropy in this compound is relatively weak [6,7]. Recent density functional theory (DFT) calculations predict that the system is multi-band in nature [12], showing a combination of q2D, 3D and several q1D bands at the Fermi level E F that could account for earlier evidence of unconventional behavior in the thermal conductivity and heat capacity [6,7]. Aside from superconductivity, no other bulk properties show clear thermodynamic evidence for an additional order parameter, raising the possibility that there may not be any other broken symmetry proximal to superconductivity.…”

Evidence for nodal superconductivity in a layered compound Ta4Pd3Te16

“…Therefore, it maybe helpful to study samples where random defects are introduced, for example by electron irradiation. On the other hand, theoretical calculations indicate that there are complex anisotropic Fermi sheets in Ta 4 Pd 3 Te 16 , and suggest the system is far away from a magnetic instability [11]. In that sense, the complex Fermi surface maybe play an important role in leading to the anisotropic interactions which give rise to nodes.…”

“…Due to the presence of multiple Fermi surface sheets from theoretical calculations [11], we also fitted various twoband models. In a phenomenological two-band model, the total superfluid density ρ s (T ) can be obtained from a linear combination of different two components:…”

“…It possesses a layered crystal structure as well as quasi-one-dimensional (Q1D) characteristics, with chains running along the b axis. Band structure calculations for Ta 4 Pd 3 Te 16 reveal that its Fermi surface consists of four branches, including two one-dimensional nested sheets, a two-dimensional cylindrical sheet and a three-dimensional one, which drives this compound to be an anisotropic but three-dimensional metal [11]. This is also consistent with the results of upper critical field measurements where a moderate anisotropy of µ 0 H c2 was observed and the coherence lengths along all three axes are much larger than the interchain distance [12].…”