Electronic anisotropies revealed by detwinned angle-resolved photo-emission spectroscopy measurements of FeSe

Watson, M. D.; Haghighirad, Amir A.; Rhodes, Luke C.; Hoesch, Moritz; Kim, T. K.

doi:10.1088/1367-2630/aa8a04

Cited by 84 publications

(152 citation statements)

References 33 publications

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“…ARPES measurements deep in the nematic state do detect two sharp excitations [15,17,[22][23][24][25][26]33], and a recent polarized ARPES study [25] provided strong evidence that these two states are indeed xz-and yzdominated, by tracking them from the M to the Γ point. However, as T increases towards T nem , the two states do not merge and remain split even above T nem [15,17,[22][23][24][25][26]33]. In Ref.…”

Section: Introductionmentioning

confidence: 99%

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

Christensen

Fernandes

Chubukov

2020

Phys. Rev. Research

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We consider the electronic spectrum near M = (π, π) in the nematic phase of FeSe (T < Tnem) 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 Tnem, but remain split at T > Tnem, in apparent contradiction to the fact that in the tetragonal phase the xz and yz orbitals are degenerate. We argue that the data can be understood if we include spin-orbit coupling at the M point. We show that a finite spin-orbit coupling gives rise to the phenomenon of orbital transmutation, by which the dominant orbital character of some bands changes between T > Tnem and T Tnem. Due to this effect, one of the modes, identified as xz (yz) at T Tnem, becomes predominantly xy at T > Tnem and hence does not merge with the predominantly yz (xz) mode. Since both ARPES and STM are surface probes, we also discuss a complimentary, surface-specific scenario, which explores the hybridization between the xz and yz orbitals. This is not allowed in the bulk, but can exist at the surface. In this case, the orbital character of the modes changes from xz and yz at T Tnem to xz ± yz at T > Tnem. The two modes again do not merge at Tnem as they are split by the hybridization.

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Section: Introductionmentioning

confidence: 99%

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

Christensen

Fernandes

Chubukov

2020

Phys. Rev. Research

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“…Additionally, to study single crystals it must be possible to cleave samples mounted on the apparatus. For ARPES measurements, large strains have been applied to low-elastic-modulus materials 28 , and spring-and piezo-based devices have been used for detwinning [29][30][31][32] . In Ref.…”

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confidence: 99%

Direct observation of a uniaxial stress-driven Lifshitz transition in Sr2RuO4

et al. 2019

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Pressure represents a clean tuning parameter for traversing the complex phase diagrams of interacting electron systems 1,2 , and as such has proved of key importance in the study of quantum materials. Application of controlled uniaxial pressure has recently been shown to more than double the transition temperature of the unconventional superconductor Sr 2 RuO 4 for example 3-5 , leading to a pronounced peak in T c vs. strain whose origin is still under active debate 4,6,7 . Here, we develop a simple and compact method to apply large uniaxial pressures passively in restricted sample environments, and utilize this to study the evolution of the electronic structure of Sr 2 RuO 4 using angle-resolved photoemission. We directly visualize how uniaxial stress drives a Lifshitz transition of the γ-band Fermi surface, pointing to the key role of strain-tuning its associated van Hove singularity to the Fermi level in mediating the peak in T c 7 . Our measurements provide stringent constraints for theoretical models of the strain-tuned electronic structure evolution of Sr 2 RuO 4 . More generally, our novel experimental approach opens the door to future studies of straintuned phase transitions not only using photoemission, but also other experimental techniques where large pressure cells or piezoelectric-based devices may be difficult to implement.The layered perovskite Sr 2 RuO 4 has been extensively studied both because of its celebrated unconventional superconductivity 5,8-11 and the accuracy with which its normal state properties can be measured 12-15 and analysed [16][17][18][19] . In spite of a quarter of a century of work, there is still no consensus on the symmetry of its superconducting order parameter, or the mechanism by which the superconductivity condenses 5 . This is a major unsolved problem because its electronic structure, which is relatively simple compared to that of many other unconventional superconductors, is now known in considerable detail and its metallic state is firmly established to be a Fermi liquid below approximately 30 K 13 . A full understanding of the Sr 2 RuO 4 problem is therefore a benchmark for the progress of the fields of strongly interacting systems and unconventional superconductivity.

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“…This form of the spin orbit coupling matrix is defined in [25]. The removal of states "by hand", makes this model highly phenomenological, however, within the energy region of ±50 meV, this approach quantitatively reproduces the experimental band dispersions measured by ARPES experiments on detwinned crystals [17][18][19]. The calculation of the local density of states (LDOS), N (r, ω), measured by QPI experiments, has been discussed extensively within the literature [14,26,27].…”

Section: Methodsmentioning

confidence: 90%

“…The black line describes the Brillouin zone boundary. b) Fermi surface map of FeSe near kz = π (hν = 56 eV) measured by ARPES on a mostly detwinned sample [17]. c) Band dispersion alongMy −Γ −Mx with projected kz states.…”

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kz Selective Scattering within Quasiparticle Interference Measurements of FeSe

et al. 2019

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Quasiparticle interference (QPI) provides a wealth of information relating to the electronic structure of a material. However, it is often assumed that this information is limited to two-dimensional electronic states. Here, we provide direct evidence that out-of-plane scattering vectors can also be observed within QPI experiments. We focus on the case of FeSe, where detailed photoemission and QPI data are available. By using a three-dimensional tight binding model, fit directly to photoemission measurements, we show that the highly anisotropic scattering vectors, measured by QPI, can be directly reproduced using a model of FeSe which includes both kz = 0 and kz = π states. This result unifies both tunnelling and photoemission based experiments on FeSe and highlights the importance of out-of-plane scattering vectors within the surface sensitive technique of QPI. arXiv:1906.02150v1 [cond-mat.supr-con]

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Electronic anisotropies revealed by detwinned angle-resolved photo-emission spectroscopy measurements of FeSe

Cited by 84 publications

References 33 publications

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

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

Direct observation of a uniaxial stress-driven Lifshitz transition in Sr2RuO4

kz Selective Scattering within Quasiparticle Interference Measurements of FeSe

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