Sign-Reversing Orbital Polarization in the Nematic Phase of FeSe due to the<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mi>C</mml:mi><mml:mn>2</mml:mn></mml:msub></mml:math>Symmetry Breaking in the Self-Energy

Onari, Seiichiro; Yamakawa, Youichi; Kontani, Hiroshi

doi:10.1103/physrevlett.116.227001

Cited by 112 publications

(171 citation statements)

References 52 publications

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“…Based on this self-consistent vertex correction (SC-VC) theory, we can explain the strong orbital fluctuations, which are measured by the softening of C 66 and Raman study [27], and the sign-reversing orbital polarization in k space below T S in FeSe [28]. This attractive orbital-order scenario is confirmed by the present study for various Fe-based superconductors.…”

Section: Introductionsupporting

confidence: 79%

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In-plane anisotropy of transport coefficients in electronic nematic states: Universal origin of nematicity in Fe-based superconductors

Onari

Kontani

2017

Phys. Rev. B

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The origin of the electronic nematicity and its remarkable material dependence are famous longstanding unsolved issues in Fe-based superconductors. To attack these issues, we focus on the in-plane anisotropy of the resistivity: In the nematic state in FeSe, the relation ρ x > ρ y holds, where ρ x(y) is the resistivity along the longer (shorter) Fe-Fe axis. In contrast, the opposite anisotropy ρ x < ρ y is realized in other undoped Fe-based superconductors. Such nontrivial material dependence is naturally explained in terms of the strongly orbitaldependent inelastic quasiparticle scattering realized in the orbital-ordered state. The opposite anisotropy between FeSe (ρ x > ρ y ) and other undoped compounds (ρ x < ρ y ) reflects the difference in the number of hole pockets. We also explain the large in-plane anisotropy of the thermoelectric power in the nematic state.

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Section: Introductionsupporting

confidence: 79%

“…At T = T N , α s = 1 is satisfied. We also calculate the self-energy matrixˆ (k) = T N qV (q)Ĝ(k − q), whereĜ is the Green's function matrix, andV is the interaction matrix for the self-energy [7,26,28]. We employ the RPA forV , and calculateĜ = [(Ĝ 0 ) −1 −ˆ ] −1 andˆ self-consistently.…”

Section: Introductionmentioning

confidence: 99%

In-plane anisotropy of transport coefficients in electronic nematic states: Universal origin of nematicity in Fe-based superconductors

Onari

Kontani

2017

Phys. Rev. B

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“…However no enhancement of SFs was found close to the nematic transition. It led to the suggestion that nematic state in β-FeSe is driven by orbital degrees of freedom [34][35][36][37].In this Rapid Communication, we report the investigations of nematic order in the normal and superconducting states of β-FeSe. We show that gluing the sample introduces random local strains (defects) and significantly smears out the otherwise sharp nematic transition resulting in the enhanced onset of nematic ordering.…”

mentioning

confidence: 86%

Nematicity and in-plane anisotropy of superconductivity inβ−FeSedetected bySe77nuclear magnetic resonance

Baek

Efremov

et al. 2016

Phys. Rev. B

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The recent study of 77 Se nuclear magnetic resonance (NMR) in a β-FeSe single crystal proposed that ferro-orbital order breaks the 90• C4 rotational symmetry, driving nematic ordering. Here, we report an NMR study of the impact of small strains generated by gluing on nematic state and spin fluctuations. We observe that the local strains strongly affect the nematic transition, considerably enhancing its onset temperature. On the contrary, no effect on low-energy spin fluctuations was found. Furthermore we investigate the interplay of the nematic phase and superconductivity. Our study demonstrates that the twinned nematic domains respond unequivalently to superconductivity, evidencing the twofold C2 symmetry of superconductivity in this material. The obtained results are well understood in terms of the proposed ferro-orbital order.Many experiments have established the existence of nematic order -a state that spontaneously breaks the rotational symmetry while time-reversal invariance is preserved -in Fe-based superconductors (FeSCs) [1][2][3][4][5][6][7][8]. Although whether spin or orbital degrees of freedom drive the nematic order is still under debate [9][10][11][12][13][14][15], it is widely believed that a nematic instability is an important characteristic of the normal state from which superconductivity emerges. Therefore establishing the mechanism of the nematic order will help to elucidate the Cooper pair glue in FeSCs.In most FeSCs, the nematic state arises in the vicinity of a spin-density wave state. The temperature (T ) interval separating them is small. As a result the strong interaction of various degrees of freedom hides the nature of the nematic order. The only exception is β-FeSe which has a PbO-type crystal structure. The nematic order occurs at T nem ≈ 91 K and at a lower temperature of T c ≈ 9 K SC sets in. The absence of static magnetism in the whole interval of temperature together with its simple structure [16] make β-FeSe the primary object for investigation of nematicity and its interplay with SC [14,[17][18][19][20][21][22][23][24][25][26]. To other spectacular properties of β-FeSe belongs the dramatic increase in T c under pressure [27,28] or by growing mono layer films on substrates [29][30][31].The band structure of β-FeSe is typical for FeSC [32,33]. The low energy is given by two hole bands around the Γ point and two electron bands around the M point. The nesting between the electron and the hole bands advocates strong spin fluctuations (SFs) at low T which indeed were observed in nuclear magnetic resonance (NMR) and neutron studies at T ≪ T nem . However no enhancement of SFs was found close to the nematic transition. It led to the suggestion that nematic state in β-FeSe is driven by orbital degrees of freedom [34][35][36][37].In this Rapid Communication, we report the investigations of nematic order in the normal and superconducting states of β-FeSe. We show that gluing the sample introduces random local strains (defects) and significantly smears out the otherwise sharp nematic tran...

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“…30,31) Here, δE nem = E zx − E yz is the orbital energy splitting at the Γ and M points. We set δE Γ nem = −0.05 eV and δE M nem = 0.15 eV.…”

Section: Superconductivity In Orthorhombic Statementioning

confidence: 99%

Fermi Surface, Pressure-Induced Antiferromagnetic Order, and Superconductivity in FeSe

et al. 2018

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The pressure dependence of the structural (Ts), antiferromagnetic (Tm), and superconducting (Tc) transition temperatures in FeSe is investigated on the basis of the 16-band d-p model. At ambient pressure, a shallow hole pocket disappears due to the correlation effect, as observed in the angular-resolved photoemission spectroscopy (ARPES) and quantum oscillation (QO) experiments, resulting in the suppression of the antiferromagnetic order, in contrast to the other iron pnictides. The orbital-polarization interaction between the Fe d orbital and Se p orbital is found to drive the ferro-orbital order responsible for the structural transition without accompanying the antiferromagnetic order. The pressure dependence of the Fermi surfaces is derived from the first-principles calculation and is found to well account for the opposite pressure dependences of Ts and Tm, around which the enhanced orbital and magnetic fluctuations cause the double-dome structure of the eigenvalue λ in the Eliashberg equation, as consistent with that of Tc in FeSe.

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Sign-Reversing Orbital Polarization in the Nematic Phase of FeSe due to theC2Symmetry Breaking in the Self-Energy

Cited by 112 publications

References 52 publications

In-plane anisotropy of transport coefficients in electronic nematic states: Universal origin of nematicity in Fe-based superconductors

In-plane anisotropy of transport coefficients in electronic nematic states: Universal origin of nematicity in Fe-based superconductors

Nematicity and in-plane anisotropy of superconductivity inβ−FeSedetected bySe77nuclear magnetic resonance

Fermi Surface, Pressure-Induced Antiferromagnetic Order, and Superconductivity in FeSe

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