{"title":"单层 CoN 和 CoP 的拓扑和超导特性:第一原理比较研究","authors":"Jiaqing Gao, Zhenyu Zhang, Ping Cui","doi":"10.1007/s11433-023-2324-0","DOIUrl":null,"url":null,"abstract":"<p>Two-dimensional systems that simultaneously harbor superconductivity and nontrivial band topology may serve as appealing platforms for realizing topological superconductivity with promising applications in fault-tolerant quantum computing. Here, based on first-principles calculations, we show that monolayered CoN and CoP with the isovalent FeSe-like structure are stable in freestanding form, even though their known bulk phases have no resemblance to layering. The two systems are further revealed to display intrinsic band inversions due to crystal field splitting, and such orderings are preserved with the inclusion of spin-orbit coupling (SOC), which otherwise is able to open a curved band gap, yielding a non-zero <i>Z</i><sub>2</sub> topological invariant in each case. Such a mechanism of topologicalization is distinctly contrasted with that identified recently for the closely related monolayers of CoX (X = As, Sb, Bi), where the SOC plays an indispensable role in causing a nontrivial band inversion. Next, we demonstrate that, by applying equi-biaxial tensile strain, the electron-phonon coupling strength in monolayered CoN can be significantly enhanced, yielding a superconducting transition temperature (<i>T</i><sub>c</sub>) up to 7–12 K for the Coulomb pseudopotential of <i>μ*</i> = 0.2–0.1, while the CoP monolayer shows very low <i>T</i><sub>c</sub> even under pronounced strain. Their different superconducting behaviors can be attributed to different variations in lattice softening and electronic density of states around the Fermi level upon pressuring. Our central findings enrich the understanding of different mechanisms of band inversions and topologicalization and offer platforms for achieving the coexistence of superconductivity and nontrivial band topology based on two-dimensional systems.</p>","PeriodicalId":774,"journal":{"name":"Science China Physics, Mechanics & Astronomy","volume":null,"pages":null},"PeriodicalIF":6.4000,"publicationDate":"2024-04-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":"{\"title\":\"Topological and superconducting properties of monolayered CoN and CoP: A first-principles comparative study\",\"authors\":\"Jiaqing Gao, Zhenyu Zhang, Ping Cui\",\"doi\":\"10.1007/s11433-023-2324-0\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"<p>Two-dimensional systems that simultaneously harbor superconductivity and nontrivial band topology may serve as appealing platforms for realizing topological superconductivity with promising applications in fault-tolerant quantum computing. Here, based on first-principles calculations, we show that monolayered CoN and CoP with the isovalent FeSe-like structure are stable in freestanding form, even though their known bulk phases have no resemblance to layering. The two systems are further revealed to display intrinsic band inversions due to crystal field splitting, and such orderings are preserved with the inclusion of spin-orbit coupling (SOC), which otherwise is able to open a curved band gap, yielding a non-zero <i>Z</i><sub>2</sub> topological invariant in each case. Such a mechanism of topologicalization is distinctly contrasted with that identified recently for the closely related monolayers of CoX (X = As, Sb, Bi), where the SOC plays an indispensable role in causing a nontrivial band inversion. Next, we demonstrate that, by applying equi-biaxial tensile strain, the electron-phonon coupling strength in monolayered CoN can be significantly enhanced, yielding a superconducting transition temperature (<i>T</i><sub>c</sub>) up to 7–12 K for the Coulomb pseudopotential of <i>μ*</i> = 0.2–0.1, while the CoP monolayer shows very low <i>T</i><sub>c</sub> even under pronounced strain. Their different superconducting behaviors can be attributed to different variations in lattice softening and electronic density of states around the Fermi level upon pressuring. Our central findings enrich the understanding of different mechanisms of band inversions and topologicalization and offer platforms for achieving the coexistence of superconductivity and nontrivial band topology based on two-dimensional systems.</p>\",\"PeriodicalId\":774,\"journal\":{\"name\":\"Science China Physics, Mechanics & Astronomy\",\"volume\":null,\"pages\":null},\"PeriodicalIF\":6.4000,\"publicationDate\":\"2024-04-11\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"\",\"citationCount\":\"0\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"Science China Physics, Mechanics & Astronomy\",\"FirstCategoryId\":\"101\",\"ListUrlMain\":\"https://doi.org/10.1007/s11433-023-2324-0\",\"RegionNum\":1,\"RegionCategory\":\"物理与天体物理\",\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"\",\"PubModel\":\"\",\"JCR\":\"Q1\",\"JCRName\":\"PHYSICS, MULTIDISCIPLINARY\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"Science China Physics, Mechanics & Astronomy","FirstCategoryId":"101","ListUrlMain":"https://doi.org/10.1007/s11433-023-2324-0","RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"PHYSICS, MULTIDISCIPLINARY","Score":null,"Total":0}
Topological and superconducting properties of monolayered CoN and CoP: A first-principles comparative study
Two-dimensional systems that simultaneously harbor superconductivity and nontrivial band topology may serve as appealing platforms for realizing topological superconductivity with promising applications in fault-tolerant quantum computing. Here, based on first-principles calculations, we show that monolayered CoN and CoP with the isovalent FeSe-like structure are stable in freestanding form, even though their known bulk phases have no resemblance to layering. The two systems are further revealed to display intrinsic band inversions due to crystal field splitting, and such orderings are preserved with the inclusion of spin-orbit coupling (SOC), which otherwise is able to open a curved band gap, yielding a non-zero Z2 topological invariant in each case. Such a mechanism of topologicalization is distinctly contrasted with that identified recently for the closely related monolayers of CoX (X = As, Sb, Bi), where the SOC plays an indispensable role in causing a nontrivial band inversion. Next, we demonstrate that, by applying equi-biaxial tensile strain, the electron-phonon coupling strength in monolayered CoN can be significantly enhanced, yielding a superconducting transition temperature (Tc) up to 7–12 K for the Coulomb pseudopotential of μ* = 0.2–0.1, while the CoP monolayer shows very low Tc even under pronounced strain. Their different superconducting behaviors can be attributed to different variations in lattice softening and electronic density of states around the Fermi level upon pressuring. Our central findings enrich the understanding of different mechanisms of band inversions and topologicalization and offer platforms for achieving the coexistence of superconductivity and nontrivial band topology based on two-dimensional systems.
期刊介绍:
Science China Physics, Mechanics & Astronomy, an academic journal cosponsored by the Chinese Academy of Sciences and the National Natural Science Foundation of China, and published by Science China Press, is committed to publishing high-quality, original results in both basic and applied research.
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