Ti-based superconductors: Progress and perspectives

Abstract

Over the past few decades, superconductivity has been a central focus of condensed matter physics and materials science due to its remarkable physical origins and great potential applications. Reflecting on the history of superconductivity, the emergence of new material systems and the discovery of new quantum states set the milestones in its development. On one hand, the emergence of new material systems has sparked exploration into the physical origins of unconventional superconductivity. Apart from BCS superconductors, the pairing mechanism of Cooper pairs has remained a challenging problem in unconventional superconductors, such as Cu-based (cuprates), Fe-based, and heavy-fermion superconductors. On the other hand, the discovery of new superconducting quantum states can deepen the fundamental understanding and expand the application domains of superconductivity. Examples include topological superconductivity for constructing quantum computers and two-dimensional (2D) superconductivity for novel quantum devices. Noteworthily, Titanium (Ti:3d² 4s²) based superconductors have garnered great attention in recent years due to their various unconventional superconducting phenomena. Given its multifaceted characteristics, the family of Ti-based superconductors encompasses various superconducting pairing mechanisms and exhibits intriguing quantum states. This work provides an overview of the crystal structure, electronic structure, and superconducting properties of those Ti-based superconductors. Several cutting-edge topics, including 2D superconductivity, topological superconductivity, and the interplay between superconductivity and magnetism, have been discussed within the Ti-based family. It is worth noting that such rich, unconventional superconducting phenomena are dominated by the same element, Ti, which may help us explore the origin of unconventional superconductivity and induce novel superconducting quantum states. The challenges and opportunities of Ti-based superconductors are discussed.

Keywords

Titanium / Metal and insulators / Unconventional superconductivity / Magnetism / Topological superconductivity

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

CRediT authorship contribution statement

Rongji Wang: Writing – original draft. Jian Zhang: Writing – original draft. Wanfeng Shi: Writing – original draft. Yan Du: Writing – original draft. Yu Ding: Writing – original draft. Baotong Qi: Writing – original draft. Ruicheng Liu: Writing – original draft. Yangyu Zhu: Writing – original draft. Yangyang Li: Writing – review & editing, Supervision, Conceptualization.

Acknowledgements

This work was supported by the National Natural Science Foundation of China (No. 12204270), the Natural Science Foundation of Shandong Province (2023HWYQ-042), the Taishan Scholar Foundation of Shandong Province (tsqn202306048), Xiaomi Young Talents Program and the Qilu Young Scholar Program of Shandong University, Core Facility Sharing Platform of Shandong University, and National Demonstration Center for Experimental Physics Education (Shandong University).

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