Optical absorption of an interacting many-polaron gas

Tempere, J.; Devreese, Jozef T.

doi:10.1103/physrevb.64.104504

Cited by 72 publications

(132 citation statements)

References 46 publications

(100 reference statements)

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“…A decay of the short-lived (ps timescale) excitons created in the initial photoabsorption process leads to polaron formation. For ZnO, a wide-bandgap metal oxide with desirable physical and chemical properties, only indirect experimental 2 and limited theoretical 4,5 information on the existence of polarons is available: theoretical description of large (weak coupling) electron polarons agrees with experimental observation 2,5 ; and small (strong coupling) polarons are not stable 6 . This contrasts with excitons, which have been studied in detail and whose lifetimes (around 60 ps (ref.…”

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confidence: 99%

Evidence for photogenerated intermediate hole polarons in ZnO

et al. 2015

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Despite their pronounced importance for oxide-based photochemistry, optoelectronics and photovoltaics, only fairly little is known about the polaron lifetimes and binding energies. Polarons represent a crucial intermediate step populated immediately after dissociation of the excitons formed in the primary photoabsorption process. Here we present a novel approach to studying photoexcited polarons in an important photoactive oxide, ZnO, using infrared (IR) reflection-absorption spectroscopy (IRRAS) with a time resolution of 100 ms. For welldefined (10-10) oriented ZnO single-crystal substrates, we observe intense IR absorption bands at around 200 meV exhibiting a pronounced temperature dependence. On the basis of first-principles-based electronic structure calculations, we assign these features to hole polarons of intermediate coupling strength.

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confidence: 99%

Evidence for photogenerated intermediate hole polarons in ZnO

et al. 2015

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“…17 In the former case those peaks were tentatively assigned to polarons, in the latter case to disorder effects related to the Sr impurities. However, either for isolated 18 or for interacting polarons 19,20 the main absorption is predicted at frequencies higher than ω LO , where LO is a longitudinal optical mode of the polar lattice. As ω LO > ω 1 TO , the peaks observed in Figs.…”

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confidence: 99%

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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“…These results along with optical- [5][6][7] and neutron-scattering 8,9 spectroscopies unambiguously show that lattice vibrations play a significant but unconventional role in high-temperature superconductivity. The interpretation of the optical spectra of high-T c materials as due to many-polaron absorption 10 strengthens the view 11 that the Fröhlich EPI is important in those structures. Operating together with a short-range deformation potential and molecular-type ͑e.g., Jahn-Teller 12 ͒ EPIs, the Fröhlich EPI can readily overcome the Coulomb repulsion at a short distance of about the lattice constant for electrons to form realspace intersite bipolarons or Cooper pairs depending on doping.…”

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confidence: 73%