摘要
The Lieb lattice, characterized by its distinctive Dirac cone and flat-band electronic structures, hosts a variety of exotic physical phenomena. However, its realization remains largely confined to artificial lattices. In this work, we propose the concept of a Lieb electride, where the non-bound electrons gather at the middle edges,behaving as the quasi-atoms of a Lieb lattice, enabling the emergence of flat bands. Using crystal structure prediction method MAGUS and first-principles calculations, we predict a stable candidate, Ca_(2)I, at ambient pressure. Distinct from conventional electrides with localized electrons at cavity centers, Ca_(2)I features interstitial electrons situated at cavity edges. The resultant flat bands lie close to the Fermi level, giving rise to a pronounced peak in the density of states and leading to Stoner-type ferromagnetism. With increasing pressures, we observe quantum phase transitions from ferromagnetic to non-magnetic and finally to antiferromagnetic orders in Ca_(2)I.Intriguingly, superconductivity emerges in the antiferromagnetic region, suggesting potential competition between these correlated states. Our study not only extends the concepts of electrides but also provides a novel strategy for realizing Lieb lattices through non-bound electrons. This work establishes Ca_(2)I as a promising platform for exploring flat-band physics and correlated electronic states, opening avenues for novel quantum phenomena in electride-based materials.
基金
supported by the National Natural Science Foundation of China(Grant Nos.12125404,T2495231,123B2049,and 12204138)
the National Key R&D Program of China(Grant No.2022YFA1403201)
the Advanced MaterialsNational Science and Technology Major Project (Grant No.2024ZD0607000)
the Basic Research Program of Jiangsu (Grant Nos.BK20233001 and BK20241253)
the Jiangsu Funding Program for Excellent Postdoctoral Talent (Grant Nos.2024ZB002,2024ZB075,2025ZB440 and2025ZB852)
the China Postdoctoral Science Foundation (Grant No.2025M773331)
the Postdoctoral Fellowship Program of CPSF (Grant No.GZC20240695 and GZC20252202)
the AI&AI for Science Program of Nanjing University
Artificial Intelligence and Quantum physics (AIQ) program of Nanjing University
the Fundamental Research Funds for the Central Universities。
