Superconductivity in the Topological Nodal-line Semimetal NaAlSi

Abstract

NaAlSi is an sp electron superconductor crystallizing in a layered structure of the anti-PbFCl type with a relatively high transition temperature Tc of ~7 K. Recent electronic state calculations revealed the presence of topological nodal lines in the semimetallic band structure, which attracted much attention owing to the superconductivity. However, experimental investigation remained limited because of the lack of single crystals. Here, we successfully prepared single crystals of NaAlSi by a Na-Ga flux method and characterized their superconducting and normal-state properties through electrical resistivity, magnetization, and heat capacity measurements. A sharp superconducting transition with a Tc of 6.8 K is clearly observed, and heat capacity data suggest an anisotropic superconducting gap. Surprisingly, despite the sp electron system, the normal state is governed by the electron correlations, which is indicated by a T2 resistivity and a Wilson ratio of 2.0. The origin of the electron correlation may be related to the orthogonal saddle-shaped Fermi surfaces derived from the Si px and py states, which intersect with the light Al s bands to form the nodal lines near the Fermi level. These results strongly suggest that the superconductivity of NaAlSi is not caused by a simple phonon mechanism but involves a certain unconventional aspect, although its relevance to the nodal lines is unclear.

References in corpus (4)

• LiFeAs: An Intrinsic FeAs-based Superconductor with Tc = 18K
• Structure and superconductivity of LiFeAs
• Rattling-Induced Superconductiviy in the Beta-Pyrochlore Oxides AOs2O6
• The upper critical field and its anisotropy in LiFeAs

Cited by in corpus (12)

• Euler Obstructed Cooper Pairing: Nodal Superconductivity and Hinge Majorana Zero Modes
• Spectroscopic Evidence for Dirac Nodal Surfaces and Nodal Rings in Superconductor NaAlSi
• Unusual Resistive Transitions in the Nodal-Line Semimetallic Superconductor NaAlSi
• Experimental detection of topological electronic state and large linear magnetoresistance in $SrS{n}_4$ superconductor
• Pseudogap Formation in the Nodal-Line Semimetal NaAlGe
• Spatially Dependent in-Gap States Induced by Andreev Tunneling through a Single Electronic State
• Pressure evolution of the normal- and superconducting-state properties of the line-nodal material CaSb${}_2$ revealed by ${}^{123}$Sb nuclear quadrupole resonance
• Delicate Superconductivity in NaAlGe Single Crystal
• Interfaces of nodal-line semimetals: drum states, transport and refraction
• Coexisting electronic smectic liquid crystal and superconductivity in a Si square-net semimetal
• Topological Semimetal KAlGe with Novel Electronic Instability
• Coexistence of stripe order and superconductivity in NaAlSi