Large magnetoresistance and superconductivity in α-gallium single crystals

• Published in: npj quantum materials 2018-08, Vol.3 (1), Article 40
• Main Authors: Chen, Bin, Duan, Xu, Wang, Hangdong, Du, Jianhua, Zhou, Yuxing, Xu, Chunqiang, Zhang, Yukun, Zhang, Liyao, Wei, Meng, Xia, Zhengcai, Cao, Chao, Dai, Jianhui, Fang, Minghu, Yang, Jinhu
• Format: Article
• Language: English
• Subjects: 639/301; 639/301/119/2792; Band structure of solids; Condensed Matter Physics; Crystal growth; Current carriers; Cyclotrons; Fermions; First principles; Gallium; Liquid phases; Low temperature; Magnetic properties; Magnetoresistance; Magnetoresistivity; Mathematical analysis; Metalloids; Physics; Physics and Astronomy; Pressure; Quantum mechanics; Quantum Physics; Room temperature; Single crystals; Structural Materials; Superconductivity; Surfaces and Interfaces; Temperature; Thin Films; Topology
• ISSN: 2397-4648; 2397-4648
• DOI: 10.1038/s41535-018-0114-3

Topological metals, including Dirac and Weyl semimetals, represent a wide class of quantum materials with non-trivial electronic band structures. The essential properties of Dirac or Weyl fermions, including light effective mass and high mobility, have been observed in a number of semimetal compounds, which in turn exhibit large positive magnetoresistances. Here, we report an unexpected observation of all these properties in α -gallium (α-Ga) single crystals, a pure metal that is in the liquid phase at room temperature and ambient pressure. Based on systematical transport measurements, α -Ga single crystal is found to exhibit large magnetoresistance, reaching about 1.66 × 10 6 per cent at 2 K in a magnetic field of 9 T. At low temperatures the de Haas–van Alphen and Shubinikov de Hass quantum oscillations show ultrahigh mobility and very small cyclotron effective mass for charge carriers, together with a non-trivial Berry phase. Combined with first-principle band structure calculations, these properties demonstrate α -Ga as a rare topological pure metal. Furthermore, superconductivity with T c of ~0.9 K is confirmed by both specific heat and resistivity measurements. These findings suggest that α -Ga is a unique pure metal displaying both non-trivial topological and superconducting properties. Topological metals: Superconductivity meets topology in Ga crystals A comprehensive investigation of bulk properties of α-Ga single crystals grown using a super cooled method—Ga is a metal that is liquid at room temperature—revealed that at very low temperatures this material exhibits a number of interesting properties; in particular, topology and superconductivity coexist. Bin Chen and colleagues measured a very large magnetoresistance, accompanied by a light effective mass and high mobility for the charge carriers, properties that suggest that the material is a topological metal. This conclusion is supported by first-principle calculations. Moreover, previous measurements indicating that the material is superconducting at very low temperature were experimentally confirmed. Materials exhibiting both topological properties and superconductivity provide a useful testing ground for understanding the interplay between superconducting pairing mechanisms and topology of the electronic band structure.