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Anomalous metallic state and anisotropic multiband superconductivity in Nb3Pd0.7Se7
- Source :
- Phys. Rev. B 88, 024508 (2013)
- Publication Year :
- 2013
-
Abstract
- We report the discovery of superconductivity in Nb$_3$Pd$_{x}$Se$_7$ with a $x$-dependent superconducting transition-temperature as high as $T_c \simeq 2.1 $ K for $x \simeq0.7$ (middle point of the resistive transition). Needle-like single crystals display anisotropic upper-critical fields with an anisotropy $\gamma = H^{b}_{c2}/H^{a}_{c2}$ as large as 6 between fields applied along their needle axis (or $b-$axis) or along the $a-$axis. As for the Fe based superconductors $\gamma$ is temperature-dependent suggesting that Nb$_3$Pd$_{0.7}$Se$_7$ is a multi-band superconductor. This is supported by band structure calculations which reveal a Fermi surface composed of quasi-one-dimensional and quasi-two-dimensional sheets of hole character, as well as three-dimensional sheets of both hole- and electron-character. Remarkably, $H^{b}_{c2}$ is observed to saturate at $H^{b}_{c2}(T \rightarrow 0 \text{K}) \simeq 14.1$ T which is $4.26 \times H_p$ where $H_p$ is the Pauli-limiting field in the weak-coupling regime. The synthesis procedure yields additional crystals belonging to the Nb$_2$Pd$_{x}$Se$_5$ phase which also becomes superconducting when the fraction of Pd is varied. For both phases we find that superconductivity condenses out of an anomalous metallic state, i.e. displaying $\partial \rho/ \partial T < 0$ above $T_c$ similarly to what is observed in the pseudogap-phase of the underdoped cuprates. An anomalous metallic state, low-dimensionality, multi-band character, extremely high and anisotropic $H_{c2}$s, are all ingredients for unconventional superconductivity.<br />Comment: 9 pages, 7 figures, to appear in Physical Review B
- Subjects :
- Condensed Matter - Superconductivity
Subjects
Details
- Database :
- arXiv
- Journal :
- Phys. Rev. B 88, 024508 (2013)
- Publication Type :
- Report
- Accession number :
- edsarx.1306.6868
- Document Type :
- Working Paper
- Full Text :
- https://doi.org/10.1103/PhysRevB.88.024508