Unconventional localization of electrons inside of a nematic electronic phase

Liam S. Farrar, Zachary Zajicek, Archie B. Morfoot, Matthew Bristow, Oliver S. Humphries, Amir A. Haghighirad, Alix McCollam, Simon J. Bending, Amalia I. Coldea

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The magnetotransport behavior inside the nematic phase of bulk FeSe reveals unusual multiband effects that cannot be reconciled with a simple two-band approximation proposed by surface-sensitive spectroscopic probes. In order to understand the role played by the multiband electronic structure and the degree of two-dimensionality, we have investigated the electronic properties of exfoliated flakes of FeSe by reducing their thickness. Based on magnetotransport and Hall resistivity measurements, we assess the mobility spectrum that suggests an unusual asymmetry between the mobilities of the electrons and holes, with the electron carriers becoming localized inside the nematic phase. Quantum oscillations in magnetic fields up to 38 T indicate the presence of a hole-like quasiparticle with a lighter effective mass and a quantum scattering time three times shorter, as compared with bulk FeSe. The observed localization of negative charge carriers by reducing dimensionality can be driven by orbitally dependent correlation effects, enhanced interband spin fluctuations, or a Lifshitz-like transition, which affect mainly the electron bands. The electronic localization leads to a fragile two-dimensional superconductivity in thin flakes of FeSe, in contrast to the two-dimensional high-Tc induced with electron doping via dosing or using a suitable interface.

Original languageEnglish
Article numbere2200405119
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number43
Early online date18 Oct 2022
Publication statusPublished - 25 Oct 2022

Bibliographical note

Funding Information:
ACKNOWLEDGMENTS. We thank Steve Simon and Siddharth Parameswar for useful discussions and Roemer Hinlopen for the development of the software used to estimate the scattering-path length for an arbitrary Fermi surface. The research was funded by the Oxford Centre for Applied Superconductivity at Oxford University. We also acknowledge financial support from the John Fell Fund of Oxford University. This work was partly supported by Engineering and Physical Sciences Research Council (EPSRC) Grants EP/I004475/1 and EP/I017836/1. L.S.F. was supported by the Bath/Bristol Centre for Doctoral Training in Condensed Matter Physics, under the EPSRC Grant EP/L015544. Part of this work was supported by High Field Magnet Laboratory– Radboud University Nijmegen/Foundation for Fundamental Research on Matter, members of the European Magnetic Field Laboratory (EMFL), and EPSRC via its membership to EMFL Grant EP/N01085X/1. A.A.H. acknowledges financial support of Oxford Quantum Materials Platform Grant EP/M020517/1. Z.Z. acknowledges financial support from EPSRC Studentships EP/N509711/1 and EP/R513295/1. A.I.C. acknowledges EPSRC Career Acceleration Fellowship EP/I004475/1.


  • Fermi surface
  • magnetotransport
  • quantum oscillations
  • thin flakes
  • unconventional superconductors

ASJC Scopus subject areas

  • General


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