Title: Ab initio study of cross-interface electron-phonon couplings in FeSe thin films on ${\mathrm{SrTiO}}_3$ and ${\mathrm{BaTiO}}_3$

Abstract

We study the electron-phonon coupling strength near the interface of monolayer and bilayer FeSe thin films on SrTiO ₃ , BaTiO ₃ , and oxygen-vacant SrTiO ₃ substrates, using ab initio methods. The calculated total electron-phonon coupling strength λ = 0.2 – 0.3 cannot account for the high T _c ~ 70 K observed in these systems through the conventional phonon-mediated pairing mechanism. In all of these systems, however, we find that the coupling constant of a polar oxygen branch peaks at q = 0 with negligible coupling elsewhere, while the energy of this mode coincides with the offset energy of the replica bands measured recently by angle-resolved photoemission spectroscopy experiments. However, the integrated coupling strength for this mode from our current calculations is still too small to produce the observed high T _c , even through the more efficient pairing mechanism provided by the forward scattering. Also, we arrive at the same qualitative conclusion when considering a checkerboard antiferromagnetic configuration in the Fe layer. In light of the experimental observations of the replica band feature and the relatively high T _c of FeSe monolayers on polar substrates, our results point towards a cooperative role for the electron-phonon interaction, wheremore » the cross-interface interaction acts in conjunction with a purely electronic interaction. Finally, we discuss a few scenarios where the coupling strength obtained here may be enhanced.« less

Authors:

Wang, Y. ^[1]; Linscheid, A. ^[2]; Berlijn, T.  ^[3];

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Johnston, S. ^[1]

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1. Univ. of Tennessee, Knoxville, TN (United States). Dept. of Physics and Astronomy
2. Univ. of Florida, Gainesville, FL (United States). Dept. of Physics
3. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Center for Nanophase Materials Sciences, Computer Science and Mathematics Division

Publication Date:

2016-04-22

Research Org.:

Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

Sponsoring Org.:

USDOE Office of Science (SC)

OSTI Identifier:

1393894

Alternate Identifier(s):

OSTI ID: 1249680

Grant/Contract Number:  

AC05-00OR22725; FG02-05ER46236

Resource Type:

Journal Article: Accepted Manuscript

Journal Name:

Physical Review B

Additional Journal Information:

Journal Volume: 93; Journal Issue: 13; Journal ID: ISSN 2469-9950

Publisher:

American Physical Society (APS)

Country of Publication:

United States

Language:

English

Subject:

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY