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Sci Bull (Beijing). 2016;61:925-930. Epub 2016 Apr 30.

What makes the Tc of monolayer FeSe on SrTiO3 so high: a sign-problem-free quantum Monte Carlo study.

Author information

1
Institute for Advanced Study, Tsinghua University, Beijing, 100084 China.
2
International Center for Quantum Materials, School of Physics, Peking University, Beijing, 100871 China ; Collaborative Innovation Center of Quantum Matter, Beijing, 100871 China.
3
Institute for Advanced Study, Tsinghua University, Beijing, 100084 China ; Collaborative Innovation Center of Quantum Matter, Beijing, 100871 China.
4
Department of Physics, University of California, Berkeley, CA 94720 USA ; Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 USA.

Abstract

Monolayer FeSe films grown on SrTiO3 (STO) substrate show superconducting gap-opening temperatures ([Formula: see text]) which are almost an order of magnitude higher than those of the bulk FeSe and are highest among all known Fe-based superconductors. Angle-resolved photoemission spectroscopy observed "replica bands" suggesting the importance of the interaction between FeSe electrons and STO phonons. These facts rejuvenated the quest for [Formula: see text] enhancement mechanisms in iron-based, especially iron-chalcogenide, superconductors. Here, we perform the first numerically-exact sign-problem-free quantum Monte Carlo simulations to iron-based superconductors. We (1) study the electronic pairing mechanism intrinsic to heavily electron doped FeSe films, and (2) examine the effects of electron-phonon interaction between FeSe and STO as well as nematic fluctuations on [Formula: see text]. Armed with these results, we return to the question "what makes the [Formula: see text] of monolayer FeSe on SrTiO3 so high?" in the conclusion and discussions.

KEYWORDS:

FeSe/STO; High temperature superconductivity; Iron-based superconductivity; Pairing mechanism; Sign-problem-free quantum Monte-Carlo simulation

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