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Topological materials can be classified into topological insulators (TIs), topological crystalline insulators, topological Dirac semimetals, topological Weyl semimetals, topological nodal-line semimetals, and others. Such materials are attracting attention in condensed matter physics and materials science due to their intriguing physical properties and promising technological applications. For a given compound system, identification of its topological nature is generally complex, demanding specific determination of the appropriate topological invariant through detailed electronic structure and Berry curvature calculations.

The topologically nontrivial nature is tied to the appearance of inverted bands in the electronic structure. For most topological materials, band inversions have been demonstrated to be induced by delicate synergistic effects of different physical factors, including chemical bonding, crystal field and, most notably, spin-orbit coupling (SOC). In particular, for the most widely studied topological systems of three-dimensional (3D) TIs, SOC has been identified to play the vital role in inducing band inversion. Recently, several so-called high-throughput methods were successfully developed for
predictingTIs. For example, by using a certain descriptor, tens of new candidate TIs have been proposed by a research group in Duke University. Yet at the implementation level, all these approaches rely on detailed band structure calculations based on first principles.

In this cover paper, a simple and efficient criterion that allows ready screening of potential topological insulators was proposed by the collaborative team of Prof. Huijun Liu at Wuhan University, Prof. Xingqiu Chen at the Institute of Metal Research, Chinese Academy of Sciences, and Prof. Zhenyu Zhang at the University of Science and Technology of China. The criterion is inherently tied to the band inversion induced by
SOC, and is uniquely defined by a minimal number of two elemental physical properties of the constituent elements: the atomic number and Pauling electronegativity, rather than inputs from detailed computations of electronic band structures within density functional theory.

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