Title: Orbital transmutation and the electronic spectrum of FeSe in the nematic phase

Abstract

We consider the electronic spectrum near M=(π,π) in the nematic phase of FeSe (T < T_nem) and make a detailed comparison with recent ARPES and STM experiments. Our main focus is the unexpected temperature dependence of the excitations at the M point. These have been identified as having xz and yz orbital character well below T_nem, but remain split at T > T_nem, in apparent contradiction to the fact that in the tetragonal phase the xz and yz orbitals are degenerate. Here we present two scenarios which can describe the data. In both scenarios, hybridization terms present in the tetragonal phase leads to an orbital transmutation, a change in the dominant orbital character of some of the bands, between T > T_nem and T << T_nem. The first scenario relies on the spin-orbit coupling at the M point. We show that a finite spin-orbit coupling gives rise to orbital transmutation, in which one of the modes, identified as xz (yz) at T << T_nem, becomes predominantly xy at T > T_nem and hence does not merge with the predominantly yz (xz) mode. The second scenario, complementary to the first, takes into consideration the fact that both ARPES and STM aremore » surface probes. In the bulk, a direct hybridization between the xz and yz orbitals is not allowed at the M point, however, it is permitted on the surface. In the presence of a direct xz/yz hybridization, the orbital character of the xz/yz modes changes from pure xz and pure yz at T << T_nem to xz±yz at T > T_nem, i.e., the two modes again have mono-orbital character at low T, but do not merge at T_nem. We discuss how these scenarios can be distinguished in polarized ARPES experiments.« less

Authors:

Christensen, Morten H. ;

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Fernandes, Rafael M.; Chubukov, Andrey V.

Publication Date:

2020-01-06

Research Org.:

Univ. of Minnesota, Minneapolis, MN (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Basic Energy Sciences (BES). Materials Sciences & Engineering Division; USDOE Office of Science (SC), Basic Energy Sciences (BES)

OSTI Identifier:

1581211

Alternate Identifier(s):

OSTI ID: 1656924; OSTI ID: 1660773

Grant/Contract Number:  

SC0012336; SC0014402; SC0020045

Resource Type:

Published Article

Journal Name:

Physical Review Research

Additional Journal Information:

Journal Name: Physical Review Research Journal Volume: 2 Journal Issue: 1; Journal ID: ISSN 2643-1564

Publisher:

American Physical Society (APS)

Country of Publication:

United States

Language:

English

Subject:

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; Nematic order; Spin-orbit coupling; Chalcogenides; Iron-based superconductors; k dot p method; Fe-based superconductors