Evolution of a Polaron Band through the Phase Diagram of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi>Nd</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn><mml:mo>−</mml:mo><mml:mi mathvariant="italic">x</mml:mi></mml:mrow></mml:msub></mml:mrow><mml:mrow><mml:msub><mml:mrow><mml:mi>Ce</mml:mi></mml:mrow><mml:mrow><mml:mi mathvariant="italic">x</mml:mi></mml:mrow></mml:msub></mml:mrow><mml:mrow><mml:msub><mml:mrow><mml:mi>CuO</mml:mi></mml:mrow>

Lupi, S.; Maselli, P.; Capizzi, M.; Calvani, P.; Giura, P.; Roy, Pascale Le

doi:10.1103/physrevlett.83.4852

Cited by 87 publications

(103 citation statements)

References 22 publications

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“…3) [20]. The peculiar ω and T dependence of σ described above is indeed seen in the optical spectra of the electron-doped NCCO at x > ∼ 0.15 [3,4] and of the hole-doped Bi2201 [1] in the non-superconducting phase. Despite the limited amount of available data, we find quite encouraging that our approach is in remarkable agreement with experiments whenever a comparison is possible (i.e.…”

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confidence: 85%

“…The extrapolation to zero frequency of this latter spectral contribution matches well with the d.c. value σ(ω = 0, T ) as obtained from transport data. Althought this is the only case where a separate narrow Drude term is directly observed, there are other cases both in hole-and electron-doped cuprates, like La 2−x Sr x CuO 4 (LSCO, x = 0.184, 0.22) [2] and Nd 2−x Ce x CuO 4−y at x > ∼ 0.15 (NCCO) [3,4], where a strongly temperature dependent peak at a finite frequency Ω Max is observed. Moreover, in LSCO, for ω < Ω Max , σ(ω) decreases and moves away from the substantially higher d.c. value.…”

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confidence: 99%

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Anomalous Optical Absorption in the Normal State of Overdoped Cuprates Near the Charge-Ordering Instability

Caprara¹,

Castro²,

Fratini

et al. 2002

Phys. Rev. Lett.

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confidence: 99%

Anomalous Optical Absorption in the Normal State of Overdoped Cuprates Near the Charge-Ordering Instability

Caprara¹,

Castro²,

Fratini

et al. 2002

Phys. Rev. Lett.

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“…The last broad band is similar to the d band observed in Nd 2-x Ce x CuO 4 and assigned to the excitation of charges self-trapped in the polar Cu-O lattice (polarons). 12 The intensity of all these features increases for T→0 through a transfer of spectral weight from higher-to-lower energy, which can hardly be appreciated on the logarithmic scale of the figure. A mid-infrared background (MIR band) also appears in Fig.…”

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confidence: 98%

“…3). We have then subtracted 12 the phonon contribution σ ph (ω) and the background due to the bands d, MIR, and CT from σ(ω), as reconstructed from a fitting procedure, thus obtaining…”

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Phase Diagram ofLa2−xSrxC

Lucarelli¹,

Lupi²,

Ortolani³

et al. 2003

Phys. Rev. Lett.

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According to theoretical predictions, 1-3 the charges injected by doping into the Cu-O planes of high-T c superconductors may gather into fluctuating, one-dimensional structures (stripes) below a temperature T* >> T c . Their existence is confirmed indirectly by the magnetic order 4,5 attributed to the regions between the stripes, by lattice distortions detected in the Extended X-ray Absorption Fine Structure, 6 or by the opening at T* of "pseudogaps" in the density of states of the carriers. 7 However, the excitation of charge arrays in the polar Cu-O lattice should also produce strong dipole fluctuations that could be directly detected by infrared spectroscopy.The phase diagram of La 2-x Sr x CuO 4 (LSCO) is recalled in the inset of Fig. 3. The insulator-to-superconductor transition occurs 8 at x = 0.055 at T = 0, while x = 0.15 corresponds approximately to the optimum doping, where one achieves the highest-T c in LSCO. In order to explore the "stripe phase" 4 as extensively as possible, the optical conductivity σ(ω) of LSCO was determined between 295 and 30 K in seven single crystals with x = 0, 0.03, 0.05, 0.07, 0.10, 0.12, and 0.15 grown in different laboratories. The reflectivity R(ω) of the a-b planes, which include the Cu-O planes where superconductivity 1

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“…Polaronic and bipolaronic effects are found in many materials like transition metal-oxides 1 , superconducting materials 2 and conjugated polymers 3 . In the last years there has been growing experimental evidence that even in the fashionable strongly correlated materials like manganates and cuprates, aside from the unscreened Coulomb repulsion the electron-lattice interaction is extremely important 4,5 .…”

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Two-dimensional Hubbard-Holstein bipolaron

2004

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We present a diagrammatic Monte Carlo study of the properties of the Hubbard-Holstein bipolaron on a two-dimensional square lattice. With a small Coulomb repulsion, U , and with increasing electron-phonon interaction, and when reaching a value about two times smaller than the one corresponding to the transition of light polaron to heavy polaron, the system suffers a sharp transition from a state formed by two weakly bound light polarons to a heavy, strongly bound on-site bipolaron. Aside from this rather conventional bipolaron a new bipolaron state is found for large U at intermediate and large electron-phonon coupling, corresponding to two polarons bound on nearest-neighbor sites. We discuss both the properties of the different bipolaron states and the transition from one state to another. We present a phase diagram in parameter space defined by the electron-phonon coupling and U . Our numerical method does not use any artificial approximation and can be easily modified to other bipolaron models with longer range electron-phonon and/or electron-electron interaction.

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Evolution of a Polaron Band through the Phase Diagram ofNd2−xCexCuO

Cited by 87 publications

References 22 publications

Anomalous Optical Absorption in the Normal State of Overdoped Cuprates Near the Charge-Ordering Instability

Anomalous Optical Absorption in the Normal State of Overdoped Cuprates Near the Charge-Ordering Instability

Phase Diagram ofLa2−xSrxC

Two-dimensional Hubbard-Holstein bipolaron

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