Hsueh-Hui Kuo

Divergent Nematic Susceptibility in an Iron Arsenide Superconductor

Lattice Trailing the Electrons Superconducting order recedes with decreased chemical doping in a typical iron-based superconductor family. Thus, the symmetry of the material is broken by almost simultaneous antiferromagnetic and structural phase transitions. However, some pnictides also exhibit an electronic nematic transition manifested by anisotropy of the electrical resistance. Because this anisotropy occurs at the same time as the structural transition, it is not clear whether it is a consequence of the broken crystal lattice symmetry or its cause. Chu et al. (p. 710) performed constant strain experiments on the series Ba(Fe1−xCox)2As2, which can distinguish between the two scenarios, and confirm that the electrons drive the lattice transition. Electrons are shown to drive a structural transition in a pnictide superconductor. Within the Landau paradigm of continuous phase transitions, ordered states of matter are characterized by a broken symmetry. Although the broken symmetry is usually evident, determining the driving force behind the phase transition can be complicated by coupling between distinct order parameters. We show how measurement of the divergent nematic susceptibility of the iron pnictide superconductor Ba(Fe1−xCox)2As2 distinguishes an electronic nematic phase transition from a simple ferroelastic distortion. These measurements also indicate an electronic nematic quantum phase transition near the composition with optimal superconducting transition temperature.

Ubiquitous signatures of nematic quantum criticality in optimally doped Fe-based superconductors.

Discerning the nematic connection The phase diagram of any given family of iron-based superconductors is complicated: Superconductivity competes with antiferromagnetism, with a structural transition often thrown in for good measure. Transport experiments have shown that in one of these families, Ba(Fe1-xCox)2As2, a rotational electronic asymmetry, dubbed nematicity, drives the structural transition. Kuo et al. detected nematic fluctuations in five Fe-based superconductor families in the vicinity of optimal chemical doping: the doping that maximizes the superconducting transition temperature. Thus, nematicity may play a role in the mechanism of superconductivity in these compounds. Science, this issue p. 958 Transport data in five families of iron-based superconductors suggest that nematicity plays a role in superconductivity. A key actor in the conventional theory of superconductivity is the induced interaction between electrons mediated by the exchange of virtual collective fluctuations (phonons in the case of conventional s-wave superconductors). Other collective modes that can play the same role, especially spin fluctuations, have been widely discussed in the context of high-temperature and heavy Fermion superconductors. The strength of such collective fluctuations is measured by the associated susceptibility. Here we use differential elastoresistance measurements from five optimally doped iron-based superconductors to show that divergent nematic susceptibility appears to be a generic feature in the optimal doping regime of these materials. This observation motivates consideration of the effects of nematic fluctuations on the superconducting pairing interaction in this family of compounds and possibly beyond.

Measurement of the elastoresistivity coefficients of the underdoped iron arsenide Ba(Fe0.975Co0.025)2As2

A new method is presented for measuring terms in the elastoresistivity tensor

High Current Density and Low Thermal Conductivity of Atomically Thin Semimetallic WTe2

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Possible origin of the nonmonotonic doping dependence of the in-plane resistivity anisotropy of Ba(Fe1−xTx)2As2 (T = Co, Ni and Cu)

of single crystal samples with tetragonal symmetry. The technique is applied to a representative underdoped Fe-arsenide, Ba(Fe

Effect of disorder on the resistivity anisotropy near the electronic nematic phase transition in pure and electron-doped BaFe(2)As(2).

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Susceptibility Anisotropy in an Iron Arsenide Superconductor Revealed by X-Ray Diffraction in Pulsed Magnetic Fields

Co

Magnetoelastically coupled structural, magnetic, and superconducting order parameters in BaFe₂(As₁₋xPx)₂

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Temperature dependence of the excitation spectrum in the charge-density-wave ErTe3 and HoTe3 systems

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Resonant enhancement of charge density wave diffraction in the rare-earth tritellurides

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