{
  "id": "2107.06361",
  "version": "v1",
  "published": "2021-07-13T19:57:40.000Z",
  "updated": "2021-07-13T19:57:40.000Z",
  "title": "Quantum spins and hybridization in artificially-constructed chains of magnetic adatoms on a superconductor",
  "authors": [
    "Eva Liebhaber",
    "Lisa M. Rütten",
    "Gaël Reecht",
    "Jacob F. Steiner",
    "Sebastian Rohlf",
    "Kai Rossnagel",
    "Felix von Oppen",
    "Katharina J. Franke"
  ],
  "categories": [
    "cond-mat.mes-hall",
    "cond-mat.str-el",
    "cond-mat.supr-con"
  ],
  "abstract": "Magnetic adatom chains on surfaces constitute fascinating quantum spin systems. Superconducting substrates suppress interactions with bulk electronic excitations but couple the adatom spins to a chain of subgap Yu-Shiba-Rusinov (YSR) quasiparticles. Using a scanning tunneling microscope, we investigate such correlated spin-fermion systems by constructing Fe chains adatom by adatom on superconducting NbSe$_2$. The adatoms couple entirely via the substrate, retaining their quantum spin nature. In dimers, we observe that the deepest YSR state undergoes a quantum phase transition due to Ruderman-Kittel-Kasuya-Yosida interactions, a distinct signature of quantum spins. Chains exhibit coherent hybridization and band formation of the YSR excitations, indicating ferromagnetic coupling. Longer chains develop separate domains due to coexisting charge-density-wave order of NbSe$_2$. Despite the spin-orbit-coupled substrate, we find no signatures of Majoranas, possibly because quantum spins reduce the parameter range for topological superconductivity. We suggest that adatom chains are versatile systems for investigating correlated-electron physics and its interplay with topological superconductivity.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2021-07-13T19:57:40.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "magnetic adatom",
      "artificially-constructed chains",
      "hybridization",
      "superconductor",
      "surfaces constitute fascinating quantum spin"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 0,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}