Two-dimensional superconductivity in a bulk single-crystal

Abstract

Both Nb${}_3$Pd${}_x$Se${}_7$ and Ta${}_4$Pd${}_3$Te${}_{16}$ crystallize in a monoclinic point group while exhibiting superconducting transition temperatures as high as $T_c\sim 3.5$ and $\sim 4.7$ K, respectively. Disorder was claimed to lead to the extremely large upper critical fields ($H_{c2}$) observed in related compounds. Despite the presence of disorder and heavier elements, $H_{c2}$s in Ta${}_4$Pd${}_3$Te${}_{16}$ are found to be considerably smaller than those of Nb${}_3$Pd${}_x$Se${}_7$ while displaying an anomalous, non-saturating linear dependence on temperature $T$ for fields along all three crystallographic axes. In contrast, crystals of the latter compound displaying the highest $T_c$s display $H_{c2}\propto (1-T/T_c{)}^{1/2}$, which in monolayers of transition metal dichalcogenides is claimed to be evidence for an Ising paired superconducting state resulting from strong spin-orbit coupling. This anomalous $T$-dependence indicates that the superconducting state of Nb${}_3$Pd${}_x$Se${}_7$ is quasi-two-dimensional in nature. This is further supported by a nearly divergent anisotropy in upper-critical fields, i.e. $\gamma =H_{c2}^b/H_{c2}^{a^{\prime }}$, upon approaching $T_c$. Hence, in Nb${}_3$Pd${}_x$Se${}_7$ the increase of $T_c$ correlates with a marked reduction in electronic dimensionality as observed, for example, in intercalated FeSe. For the Nb compound, Density functional theory (DFT) calculations indicate that an increase in the external field produces an anisotropic orbital response, with especially strong polarization at the Pd sites when the field is perpendicular to their square planar environment. Therefore, DFT suggests the field-induced pinning of the spin to the lattice as a possible mechanism for decoupling the superconducting planes. Overall, our observations represent further evidence for unconventional superconductivity in the Pd chalcogenides.

10 pages, 6 figures

References in corpus (19)

• Evidence of Ising pairing in superconducting NbSe${}_2$ atomic layers
• Superconductivty without inversion symmetry: MnSi versus CePt_3Si
• Superconductivity protected by spin-valley locking in ion-gated MoS2
• Nearly Isotropic superconductivity in (Ba,K)Fe2As2
• S-wave/spin-triplet order in superconductors without inversion symmetry: Li${}_2$Pd${}_3$B and Li${}_2$Pt${}_3$B
• Metallic ground state in an ion-gated two-dimensional superconductor
• Superconductivity with extremely large upper critical fields in Nb2Pd0.81S5
• Superconductivity at 6 K and the violation of Pauli limit in Ta2PdxS5
• Superconductivity in a Layered Ta4Pd3Te16 with PdTe2 Chains
• Enhanced Upper Critical Fields in a New Quasi-one-dimensional Superconductor Nb2PdxSe5
• Anisotropic Superconducting Gap and Elongated Vortices with Caroli-De-Gennes-Matricon States in the New Superconductor Ta4Pd3Te16
• Controllable spin-orbit coupling and its influence on the upper critical field in the chemically doped quasi-one-dimensional Nb${}_2$PdS${}_5$ superconductor
• Anomalous metallic state and anisotropic multiband superconductivity in Nb3Pd0.7Se7
• Nodal superconductivity and superconducting dome in new layered superconductor Ta4Pd3Te16
• Electronic Structure and Upper Critical Field of Superconducting Ta${}_2$PdS${}_5$
• Multiband Te $p$ Based Superconductivity of Ta${}_4$Pd${}_3$Te${}_{16}$
• 3D-2D crossover in the naturally layered superconductor (LaSe)1.14(NbSe2)
• Anomalous hysteresis as an evidence for a magnetic field-induced chiral superconducting state in LiFeAs
• Multiband Semimetallic Electronic Structure of Superconducting Ta2PdSe5

Cited by in corpus (3)

• Superconducting Phase-Diagram of H3S under High Magnetic Fields
• Pressure induced change in the electronic state of Ta${}_4$Pd${}_3$Te${}_{16}$
• Extreme in-plane upper critical magnetic fields of heavily doped quasi-two-dimensional transition metal dichalcogenides