Unconventional Temperature Enhanced Magnetism in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mi>Fe</mml:mi><mml:mn>1.1</mml:mn></mml:msub><mml:mi>Te</mml:mi></mml:math>

Zaliznyak, Igor; Xu, Zhijun; Tranquada, J. M.; Gu, Genda; Tsvelik, A. M.; Stone, M. B.

doi:10.1103/physrevlett.107.216403

Cited by 91 publications

(164 citation statements)

References 29 publications

Supporting

Mentioning

138

Contrasting

Order By: Relevance

“…The mean-field treatment of the problem leads to qualitatively correct result for these compounds (with some important caveats [38][39][40] ). Because of this analogy we expect at low temperatures the d electrons in our model to delocalize due to the mixing with the itinerant bands through V (there are evidence of such crossover in the normal state of iron chalcogenides 41,42 ). This delocalization is described on a mean-field level by a phase transition, and the appearance a non-vanishing expectation value of b ≡ b, and can significantly change the electronic spectrum by opening a hybridization gap.…”

mentioning

confidence: 99%

Nematicity driven by hybridization in iron-based superconductors

Stanev

Littlewood

2013

Phys. Rev. B

View full text Add to dashboard Cite

In this paper we study an effective model for the normal state of iron-based superconductors. It has separate, but interacting itinerant and localized degrees of freedom, originating from the dxz and dyz, and from dxy iron orbitals respectively. At low temperatures, below a mean-field phase transition, these different states condense together in an excitonic order parameter. We show that at even lower temperature, after another phase transition, this ordered state can spontaneously break the C4 lattice symmetry and become nematic. We propose this mechanism as an explanation of the tendency towards nematicity observed in several iron-based compounds.Introduction. The discovery of high-temperature superconductivity in iron-based materials 1-3 is one of the most exciting recent developments in physics. It is almost certain that the origin of superconductivity is unconventional (i.e. driven by electron-electron interactions), and is very likely that the order parameter is unconventional as well 4,5 . The normal state properties of these materials, in contrast, at first seemed rather unremarkablea bad metal behavior at high temperatures, which can be followed by structural transition and antiferromagnetic phase at low temperatures. This simple picture was considerably complicated by the growing evidence of nematic fluctuations 6-8 or even long-range order 9 present in some compounds at temperatures well above the antiferromagnetic and structural transitions. Furthermore, this nematicity seems to be of purely electronic (rather than structural) origin 10 . Understanding this state and its connection to the other phases is an important milestone in the study of these materials.

show abstract

mentioning

confidence: 99%

Nematicity driven by hybridization in iron-based superconductors

Stanev

Littlewood

2013

Phys. Rev. B

View full text Add to dashboard Cite

show abstract

“…The excess Fe resides in an interstitial site centered above (or below) a plaquette of four Fe sites. 18,19 The magnetic interaction between an interstitial and the Fe nearest-neighbors results in locally ferromagnetic correlations 20,21 and weak localization of the charge carriers, 22 and acts as a magnetic electron donor. 22 The excess Fe concentration is anticorrelated with the superconducting volume fraction and results in short-range magnetic order.…”

mentioning

confidence: 99%

“…[35][36][37][38] A recent study on Fe 1.1 Te has shown that the localized electrons that contribute to magnetism are not isolated from the itinerant ones, but instead are entangled, as indicated by a temperature-induced enhancement of the instantaneous magnetic moment. 20 In this paper, we use Cu to replace Fe in Fe 1.1 Te, aiming to study the impact of the weakly magnetic Cu dopants on the magnetic order, which we characterize with neutron scattering. We find that Cu drives down the structural and magnetic transitions, with longrange nearly-commensurate magnetic order retained in Fe 1.06 Cu 0.04 Te, but only short-range incommensurate order in FeCu 0.1 Te.…”

mentioning

confidence: 99%

Magnetic order tuned by Cu substitution in Fe1.1−zCuzTe

Wen

et al. 2012

Phys. Rev. B

Self Cite

View full text Add to dashboard Cite

We study the effects of Cu substitution in Fe1.1Te, the non-superconducting parent compound of the iron-based superconductor, Fe1+yTe1−xSex, utilizing neutron scattering techniques. It is found that the structural and magnetic transitions, which occur at ∼ 60 K without Cu, are monotonically depressed with increasing Cu content. By 10% Cu for Fe, the structural transition is hardly detectable, and the system becomes a spin glass below 22 K, with a slightly incommensurate ordering wave vector of (0.5-δ, 0, 0.5) with δ being the incommensurability of 0.02, and correlation length of 12Å along the a axis and 9Å along the c axis. With 4% Cu, both transition temperatures are at 41 K, though short-range incommensurate order at (0.42, 0, 0.5) is present at 60 K. With further cooling, the incommensurability decreases linearly with temperature down to 37 K, below which there is a first order transition to a long-range almost-commensurate antiferromagnetic structure. A spin anisotropy gap of 4.5 meV is also observed in this compound. Our results show that the weakly magnetic Cu has large effects on the magnetic correlations; it is suggested that this is caused by the frustration of the exchange interactions between the coupled Fe spins.

show abstract

“…Therefore, a careful investigation of the wave vector and energy dependence of spin excitations across the magnetic ordering temperature can provide important information concerning the nature of the magnetic order and spin-spin correlations. For example, a recent inelastic neutron scattering study of spin excitations in one of the parent compounds of iron-based superconductors, the iron chalcogenide Fe 1.1 Te which has a bicollinear antiferromagnetic (AF) structure and Néel temperature of T N = 67 K [5][6][7][8][9][10][11], reveals that the effective spin per Fe changes from S ≈ 1 in the AF state to S ≈ 3/2 in the paramagnetic state, thus providing evidence that Fe 1.1 Te is not a conventional Heisenberg antiferromagnet but a nontrivial local moment system coupled with itinerant electrons [12].Since antiferromagnetism may be responsible for electron pairing and superconductivity in iron-based superconductors [13,14], it is important to determine if the observed anomalous spin excitation behavior in iron telluride Fe 1.1 Te is a general phenomenon in the parent compounds of iron-based superconductors. For this purpose, we study the spin excitations of another parent compound of iron-based superconductors, the iron pnictide BaFe 2 As 2 which has a collinear AF structure with T N ≈ 138 K [15][16][17][18], over a wide temperature range (0.05T N ≤ T ≤ 2.1T N ).…”

mentioning

confidence: 99%

mentioning

confidence: 99%

Temperature dependence of the paramagnetic spin excitations in BaFe2As2

et al. 2012

View full text Add to dashboard Cite

We use inelastic neutron scattering to study temperature dependence of the paramagnetic spin excitations in iron pnictide BaFe2As2 throughout the Brillouin zone. In contrast to a conventional local moment Heisenberg system, where paramagnetic spin excitations are expected to have a Lorentzian function centered at zero energy transfer, the high-energy (hω > 100 meV) paramagnetic spin excitations in BaFe2As2 exhibit spin-wave-like features up to at least 290 K (T = 2.1TN ). Furthermore, we find that the sizes of the fluctuating magnetic moments m 2 ≈ 3.6 µ 2 B per Fe are essentially temperature independent from the AF ordered state at 0.05TN to 2.1TN , which differs considerably from the temperature dependent fluctuating moment observed in the iron chalcogenide Fe1.1Te [I. A. Zaliznyak et al., Phys. Rev. Lett. 107, 216403 (2011).]. These results suggest unconventional magnetism and strong electron correlation effects in BaFe2As2. The elementary magnetic excitations (spin waves and paramagnetic spin excitations) in a ferromagnet or an antiferromagnet can provide direct information about the itinerancy of the unpaired electrons contributing to the ordered moment. In a local moment system, spin waves are usually well-defined throughout the Brillouin zone and can be accurately described by a Heisenberg Hamiltonian in the magnetically ordered state. The total moment sum rule requires that the dynamical structure factor S(q, ω), when integrated over all wave vectors (q) and energies (E =hω), is a temperature independent constant and equals to m 2 = (gµ B ) 2 S(S + 1), where g is the Landé g factor (≈ 2) and S is the spin of the system [1]. Upon increasing temperature to the paramagnetic state, spin excitations in the low-q limit can be described by a simple Lorentzian scattering function, where κ 1 is the temperature dependent inverse spin-spin correlation length and Γ is the wave vector dependent characteristic energy scale [2][3][4]. At sufficiently high temperatures above the magnetic order, spin excitations should be purely paramagnetic with no spin-wave-like correlations. Therefore, a careful investigation of the wave vector and energy dependence of spin excitations across the magnetic ordering temperature can provide important information concerning the nature of the magnetic order and spin-spin correlations. For example, a recent inelastic neutron scattering study of spin excitations in one of the parent compounds of iron-based superconductors, the iron chalcogenide Fe 1.1 Te which has a bicollinear antiferromagnetic (AF) structure and Néel temperature of T N = 67 K [5][6][7][8][9][10][11], reveals that the effective spin per Fe changes from S ≈ 1 in the AF state to S ≈ 3/2 in the paramagnetic state, thus providing evidence that Fe 1.1 Te is not a conventional Heisenberg antiferromagnet but a nontrivial local moment system coupled with itinerant electrons [12].Since antiferromagnetism may be responsible for electron pairing and superconductivity in iron-based superconductors [13,14], it is important to determine...

show abstract

Unconventional Temperature Enhanced Magnetism inFe1.1Te

Cited by 91 publications

References 29 publications

Nematicity driven by hybridization in iron-based superconductors

Nematicity driven by hybridization in iron-based superconductors

Magnetic order tuned by Cu substitution in Fe1.1−zCuzTe

Temperature dependence of the paramagnetic spin excitations in BaFe2As2

Contact Info

Product

Resources

About