Mid-infrared conductivity from mid-gap states associated with charge stripes

Homes, C. C.; Tranquada, J. M.; Li, Q.; Moodenbaugh, A. R.; Buttrey, Douglas J.

doi:10.1103/physrevb.67.184516

Cited by 50 publications

(44 citation statements)

References 55 publications

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“…Optical conductivity measurements [29][30][31][32] of the stripe-ordered phase in La 2-x Sr x NiO 4 þ y reveal a broad peak centred at 0.6-0.8 eV, with a gap (measured at the peak half-height) about half that size, consistent with localization of the charge. While nickelates develop a finite conductivity (qualifying them as bad metals) on warming through T co , a pseudogap remains, which only gradually decreases on heating to B2T co (refs 29,30,32,33).…”

Section: Discussionmentioning

confidence: 77%

Direct observation of dynamic charge stripes in La2–xSrxNiO4

Anissimova

Parshall

et al. 2014

Nat Commun

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The insulator-to-metal transition continues to be a challenging subject, especially when electronic correlations are strong. In layered compounds, such as La 2-x Sr x NiO 4 and La 2-x Ba x CuO 4 , the doped charge carriers can segregate into periodically spaced charge stripes separating narrow domains of antiferromagnetic order. Although there have been theoretical proposals of dynamically fluctuating stripes, direct spectroscopic evidence of charge-stripe fluctuations has been lacking. Here we report the detection of critical lattice fluctuations, driven by charge-stripe correlations, in La 2-x Sr x NiO 4 using inelastic neutron scattering. This scattering is detected at large momentum transfers where the magnetic form factor suppresses the spin fluctuation signal. The lattice fluctuations associated with the dynamic charge stripes are narrow in q and broad in energy. They are strongest near the charge-stripe melting temperature. Our results open the way towards the quantitative theory of dynamic stripes and for directly detecting dynamical charge stripes in other strongly correlated systems, including high-temperature superconductors such as La 2-x Sr x CuO 4 .

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Section: Discussionmentioning

confidence: 77%

Direct observation of dynamic charge stripes in La2–xSrxNiO4

Anissimova

Parshall

et al. 2014

Nat Commun

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“…This result is consistent with optical conductivity studies [169,170] which show that while the dc conductivity approaches that of a metal above room temperature, the dynamic conductivity in the disordered state never shows the response of a conventional metal.…”

Section: Charge and Spin Stripe Order In Nickelatessupporting

confidence: 80%

Neutron Scattering Studies of Antiferromagnetic Correlations in Cuprates

Tranquada

Handbook of High-Temperature Superconductivity

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Summary. Neutron scattering studies have provided important information about the momentum and energy dependence of magnetic excitations in cuprate superconductors. Of particular interest are the recent indications of a universal magnetic excitation spectrum in hole-doped cuprates. That starting point provides motivation for reviewing the antiferromagnetic state of the parent insulators, and the destruction of the ordered state by hole doping. The nature of spin correlations in stripeordered phases is discussed, followed by a description of the doping and temperature dependence of magnetic correlations in superconducting cuprates. After describing the impact on the magnetic correlations of perturbations such as an applied magnetic field or impurity substitution, a brief summary of work on electron-doped cuprates is given. The chapter concludes with a summary of experimental trends and a discussion of theoretical perspectives. IntroductionNeutron scattering has played a major role in characterizing the nature and strength of antiferromagnetic interactions and correlations in the cuprates. Following Anderson's observation [1] that La 2 CuO 4 , the parent compound of the first high-temperature superconductor, should be a correlated insulator, with moments of neighboring Cu 2+ ions anti-aligned due to the superexchange interaction, antiferromagnetic order was discovered in a neutron diffraction study of a polycrystalline sample [2]. When single-crystal samples became available, inelastic studies of the spin waves determined the strength of the superexchange, J, as well as weaker interactions, such as the coupling between CuO 2 layers. The existence of strong antiferromagnetic spin correlations above the Néel temperature, T N , has been demonstrated and explained. Over time, the quality of such characterizations has improved considerably with gradual evolution in the size and quality of samples and in experimental techniques.Of course, what we are really interested in understanding are the optimallydoped cuprate superconductors. It took much longer to get a clear picture of the magnetic excitations in these compounds, which should not be surprising

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“…Raman and MIR absorption remain and there is one-electron exchange conductivity of the same kind as for the cuprates. The MIR absorption also exist [57][58][59][60].…”

Section: Possible Explanations Of Raman and Mir Absorption For Cupratesmentioning

confidence: 99%

Conductivity in Cuprates Arises from Two Different Sources: One-Electron Exchange and Disproportionation

Larsson

2016

J Supercond Nov Magn

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Simulation of the resistivity in the normal state of doped La 2−x Sr x CuO 4 has been performed using a hopping model based on Marcus theory. The results are in substantial agreement with experimental results. At oxidative doping, Cu(III) sites are formed and electron mobility possible due to hopping: Cu(III)Cu(II) → Cu(II)Cu(III) (one-electron exchange). In the underdoped, non-metallic region, the resistivity (ρ) decreases from almost insulation at T = 0 to a minimum at about T = 100 K. ρ then increases more than linearly with T (∼ T 3/2 ) in the region 100 < T < 500 K. A photo-induced metal-metal (MM) charge transfer transition at 2 eV 2Cu(II) + hν → Cu(I) + Cu(III) is responsible for the strong absorption in the visible spectrum of La 2 CuO 4 . The down-shift of spectral density with doping (x) in La 2−x Sr x CuO 4 depends on the appearance of Cu(III) sites which makes optical as well as thermal one-electron exchange transitions possible with lower energy. Disproportionation occurs spontaneously for x > 0.06, opening up for electron pair formation. Configuration interaction between two-electron states of low chemical potential, but strong vibrational coupling, gives rise to the superconductor and pseudogaps. Data from photo-induced conductivity and absorption spectra are used in the simulation, which gives results in good agreement with experiments. Possible explanations for Raman and MIR absorption suggest themselves.

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Mid-infrared conductivity from mid-gap states associated with charge stripes

Cited by 50 publications

References 55 publications

Direct observation of dynamic charge stripes in La2–xSrxNiO4

Direct observation of dynamic charge stripes in La2–xSrxNiO4

Neutron Scattering Studies of Antiferromagnetic Correlations in Cuprates

Conductivity in Cuprates Arises from Two Different Sources: One-Electron Exchange and Disproportionation

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