Electronic structure and polarons in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mi mathvariant="normal">Ca</mml:mi><mml:mi mathvariant="normal">Mn</mml:mi><mml:msub><mml:mi mathvariant="normal">O</mml:mi><mml:mrow><mml:mn>3</mml:mn><mml:mo>−</mml:mo><mml:mi>δ</mml:mi></mml:mrow></mml:msub></mml:mrow></mml:math>single crystals: Optical data

Loshkareva, N. N.; Nomerovannaya, L. V.; Mostovshchikova, E. V.; Махнев, А. А.; Sukhorukov, Yu. P.; Solin, N. I.; Arbuzova, T. I.; Наумов, С. В.; Kostromitina, N. V.; Balbashov, A. M.; Rybina, L.N.

doi:10.1103/physrevb.70.224406

Cited by 57 publications

(39 citation statements)

References 21 publications

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“…While it is absent in our absorption spectra and very weak in the photoconductivity by Jung et al 80 , it is clearly seen in the photoconductivity spectra of Loshkareva et al 79 shown in figure 9. A possible explanation for the different shapes of the experimental spectra is that not only the G-type antiferromagnetic order, but also other antiferromagnetic orders such as C-and A-type magnetic order contribute considerably to the thermal ensemble.…”

Section: A Camno3contrasting

confidence: 51%

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Electronic structure of Pr1−xCaxMnO3

et al. 2017

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The electronic structure of Pr1−xCaxMnO3 has been investigated using a combination of firstprinciples calculations, X-ray photoelectron spectroscopy (XPS), X-ray absorption spectroscopy (XAS), electron-energy loss spectroscopy (EELS), and optical absorption. The full range of compositions, x = 0, 1/2, 1, and a variety of magnetic orders have been covered. Jahn-Teller as well as Zener polaron orders are considered. The free parameters of the local hybrid density functionals used in this study has been determined by comparison with measured XPS spectra. A model Hamiltonian, valid for the entire doping range, has been extracted. A simple local-orbital picture of the electronic structure for the interpretation of experimental spectra is provided. The comparison of theoretical calculations and different experimental spectra provide a detailed and consistent picture of the electronic structure. The large variations of measured optical absorption spectra are traced back to the coexistence of magnetic orders respectively to the occupation of local orbitals. A consistent treatment of the Coulomb interaction indicate a partial cancellation of Coulomb parameters and support the dominance of the electron-phonon coupling.

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Section: A Camno3contrasting

confidence: 51%

“…79 The calculated fundamental band gap is with 1.47 eV slightly smaller than the direct gap. In CaMnO 3 , we expect at room temperature a thermal average of different magnetic orders due to their near degeneracy.…”

Section: A Camno3mentioning

confidence: 80%

Electronic structure of Pr1−xCaxMnO3

et al. 2017

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“…For 300 K ≥ T ≥ 175 K the data are described by E a = 31 meV, while for 110 K ≥ T ≥ 70 K, the fit yields E a = 48 meV. Because the optical gap of CaMnO 3 is ∼ 1.5 eV, 12 the transport is consistent with thermal excitation of carriers from a shallow impurity level below the conduction band, most likely due to oxygen defects. 13,14 Interestingly, the linear extrapolations of the fitted curves cross right at the Néel temperature T N = 125 K. The difference in the activation energies of 17 meV is therefore associated with the formation of magnetic polarons.…”

Section: A DC Transportmentioning

confidence: 58%

“…[8][9][10][11] and CaMnO 3 (Refs. [12][13][14][15] and show that a comparison between far-infrared and dc-MR measurements can yield insights into the origin of this behavior. Interest in this system was sparked by the discovery of interface ferromagnetism for temperatures below the Néel temperature of the CaMnO 3 layers.…”

Section: Introductionmentioning

confidence: 99%

Far-infrared and dc magnetotransport of CaMnO3-CaRuO3superlattices

et al. 2011

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We report temperature and magnetic field dependent measurements of the dc resistivity and the far-infrared reflectivity (photon energies ω = 50 − 700 cm −1 ) of superlattices comprising 10 consecutive unit cells of the antiferromagnetic insulator CaMnO3, and 4 -10 unit cells of the correlated paramagnetic metal CaRuO3. Below the Néel temperature of CaMnO3, the dc resistivity exhibits a logarithmic divergence upon cooling, which is associated with a large negative, isotropic magnetoresistance. The ω → 0 extrapolation of the resistivity extracted from the FIR reflectivity, on the other hand, shows a much weaker temperature and field dependence. We attribute this behavior to scattering of itinerant charge carriers in CaRuO3 from sparse, spatially isolated magnetic defects at the CaMnO3-CaRuO3 interfaces. This field-tunable "transport bottleneck" effect may prove useful for functional metal-oxide devices.

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“…The broad maximum in optical conductivity at around 1.5 eV is typical for narrow-bandwidth manganites and is a fingerprint for small-polaron absorption. [11,14,15] This absorption band at about 1.5 eV is generally attributed to a transition between Jahn-Teller (JT) split Mn 3d e g states (Figure 1b), either occurring as an intrasite or as an intersite transition between Mn 3+ and Mn 4+ sites. [12,16,17] The transition is broadened by a polaron hopping feature at 0.5-0.8 eV and coupling to a phonon bath.…”

Section: Introductionmentioning

confidence: 99%

Evolution of Hot Polaron States with a Nanosecond Lifetime in a Manganite Perovskite

Raiser

Mildner

Ifland

et al. 2017

Advanced Energy Materials

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Understanding and controlling the relaxation process of optically excited charge carriers in solids with strong correlations is of great interest in the quest for new strategies to exploit solar energy. Usually, optically excited electrons in a solid thermalize rapidly on a femtosecond to picosecond timescale due to interactions with other electrons and phonons. New mechanisms to slow down thermalization will thus be of great significance for efficient light energy conversion, e.g., in photovoltaic devices. Ultrafast optical pump–probe experiments in the manganite Pr0.65Ca0.35MnO3, a photovoltaic, thermoelectric, and electrocatalytic material with strong polaronic correlations, reveal an ultraslow recombination dynamics on a nanosecond‐time scale. The nature of long living excitations is further elucidated by photovoltaic measurements, showing the presence of photodiffusion of excited electron–hole polaron pairs. Theoretical considerations suggest that the excited charge carriers are trapped in a hot polaron state. Escape from this state is possible via a slow dipole‐forbidden recombination process or via rare thermal fluctuations toward a conical intersection followed by a radiation‐less decay. The strong correlation between the excited polaron and the octahedral dynamics of its environment appears to be substantial for stabilizing the hot polaron.

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Electronic structure and polarons inCaMnO3−δsingle crystals: Optical data

Cited by 57 publications

References 21 publications

Electronic structure of Pr1−xCaxMnO3

Electronic structure of Pr1−xCaxMnO3

Far-infrared and dc magnetotransport of CaMnO3-CaRuO3superlattices

Evolution of Hot Polaron States with a Nanosecond Lifetime in a Manganite Perovskite

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