Anomalous optical properties of the mixed-valent lithium cuprate<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mi>LiCu</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:msub><mml:mi mathvariant="normal">O</mml:mi><mml:mn>2</mml:mn></mml:msub></mml:mrow></mml:math>

Pisarev, R. V.; Moskvin, A. S.; Kalashnikova, A.M.; Bush, A. A.; Rasing, T.H.M.

doi:10.1103/physrevb.74.132509

Cited by 22 publications

(26 citation statements)

References 19 publications

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“…The optical response of multiferroic 1D cuprate LiCu 2 O 2 has been measured by the ellipsometry method 101 and reflectivity. 102 Optical properties of LiCu 1+ Cu 2+ O 2 in the spectral range of 0.6-5.8 eV radically differ from those of all other known Cu 1+ , Cu 2+ , and mixed-valence oxide cuprates.…”

Section: Discussionmentioning

confidence: 99%

Optical spectroscopy of charge transfer transitions in multiferroic manganites, ferrites, and related insulators

Moskvin¹,

Pisarev

2010

Low Temperature Physics

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The results of theoretical and experimental studies of charge transfer (CT) transitions in multiferroic manganites, ferrites, and related insulators are reviewed. Starting with a simple cluster model approach one-center p-d and two-center d-d CT transitions, their polarization properties, the role played by structural parameters, orbital mixing, and spin degree of freedom are all addressed. Optical ellipsometry data in the spectral range of 0.6–5.8eV in perovskite and hexagonal rare-earth manganites RMnO3 and in orthorhombic manganites RMn2O5 are analyzed. Two groups of iron oxides, where Fe3+ ions occupy either only octahedral positions (BiFeO3, orhoferrites RFeO3 et al.) and materials with Fe3+ ions both in octahedral and tetrahedral positions (hematite α-Fe2O3, garnets RFe5O12, lithium ferrite LiFe5O8, Ca2Fe2O5 et al.), are discussed.

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Section: Discussionmentioning

confidence: 99%

Optical spectroscopy of charge transfer transitions in multiferroic manganites, ferrites, and related insulators

Moskvin¹,

Pisarev

2010

Low Temperature Physics

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“…However, the actual coordination of the native Cu + interchain site approaches most likely an axially distorted square, or rhombic coordination due to an extremely small interdumbbell separation ͑d Ϸ 2.86 Å͒ as compared with other O-Cu + -O dumbbell bearing compounds ͑e.g., YBa 2 CuO 6 , d Ϸ 3.8 Å͒. 13 In other words, the ZhangRice singlet within the CuO 2 chains becomes unstable with respect to a hole transfer to one of the neighboring Cu + sites. Details of this instability will be discussed elsewhere.…”

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confidence: 99%

Nonrelativistic multiferrocity in the nonstoichiometric spin-12spiral-chain cuprateLiCu2O
Moskvin¹,
Panov²,
Drechsler³
2009
Phys. Rev. B
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Puzzling multiferroic behavior observed recently in spin-1/2 one-dimensional chain cuprate LiCu 2 O 2 with edge-shared arrangement of CuO 4 plaquettes and incommensurate spiral spin ordering is consistently explained to be a result of the nonrelativistic exchange-induced electric polarization on the Cu 2+ centers substituting for the positions native for the Cu 1+ ions. These substituent centers are proven to be an effective probe of the spin incommensurability and magnetic field effects.Intensive study of magnetoelectric and multiferroic materials is stimulated both by their potential application in novel technological devices and growing interest to fundamental problems of magnetoelectric coupling which proved to be a very sensitive tool to uncover subtle details of interrelation between charge, orbital, and spin ordering. However, due to its complexity, theoretical understanding of the mechanism͑s͒ of strong magnetoelectric coupling is far from being satisfactory. Remarkable demonstration of the present day situation is provided by a hot discussion around recent observations of multiferroic behavior concomitant the incommensurate spin spiral ordering in chain cuprates LiCuVO 4 ͑Refs. 1-3͒ and LiCu 2 O 2 ͑Ref. 4͒ challenging the multiferroic community. At first sight, these cuprates seem to be prototypical examples of 1D spiral-magnetic ferroelectrics revealing the relativistic mechanism of "ferroelectricity caused by spin-currents 5 " with the textbook expression for the uniform polarization induced by a spin spiral with the wave vector Q: P ϰ ͓e 3 ϫ Q͔, where e 3 is a vector orthogonal to the spin spiral plane 6 or P ij ϰ [R ij ϫ ͓S i ϫ S j ͔], where R ij denotes the vector connecting the two sites and ͓S i ϫ S j ͔ is a local spin current. 5 However, both systems reveal a mysterious behavior with conflicting results obtained by different groups. Indeed, Yasui et al. 2 claim the LiCuVO 4 reveals clear deviations from the predictions of spin-current models 5,6 while Schrettle et al. 3 assure its applicability. In contrast to LiCuVO 4 , the LiCu 2 O 2 shows up a behavior which is obviously counterintuitive within the framework of spiralmagnetic ferroelectricity. 4 It is worth noting that at variance with Park et al., 4 Naito et al. 1 have not found any evidence for ferroelectric anomalies in LiCu 2 O 2 . Such a discrepancy one observes in microscopic model approaches as well. The relativistic LSDA calculations 7 seemingly explain the LiCuVO 4 data 3 but fail in case of LiCu 2 O 2 . However, a detailed analysis of relativistic effects for the system of e g holes in a perfect chain structure of edge-shared CuO 4 plaquettes as in LiCuVO 4 and LiCu 2 O 2 shows that the in-chain spin current does not produce an electric polarization because of an exact cancellation of two Cu-O-Cu paths. 8 Moreover, recently we have shown 9 that the multiferroicity in LiCuVO 4 may have nothing to do with relativistic effects and can be consistently explained, if the nonrelativistic exchangeinduced electric polarization on the out-of-c...

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“…Recently it was found that lithium cuprate LiCu 2 O 2 , where Cu 2+ ions occupy square-planar positions similar to those in Pr, Nd, and Sm cuprates, demonstrates anomalous optical absorption spectra. 38,39 The optical response of LiCu 2 O 2 is characterized by an extremely strong, sharp, and highly anisotropic optical feature at 3.27 eV whereas low-energy 1.6-2.1 eV features seen in R 2 CuO 4 cuprates are suppressed. An exciton-type model was suggested for explaining this feature which is based on strong electron-hole correlations and a crystal-field splitting of the Cu 1+ states.…”

Section: Discussionmentioning

confidence: 99%

Near-band gap electronic structure of the tetragonal rare-earth cupratesR2CuO4and the bismuth cuprateBi2
Pisarev
¹
,
Павлов
²
,
Kalashnikova
³

et al. 2010
Phys. Rev. B
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27
0
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0
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Complex optical dielectric function in the tetragonal rare-earth cuprates R 2 CuO 4 ͑R = La, Pr, Nd, and Sm͒ and in the tetragonal bismuth cuprate Bi 2 CuO 4 is studied in the spectral range of 0.6-5.4 eV using a method of optical ellipsometry. The dielectric spectra are studied for the two main polarizations and analyzed in terms of a cluster model for CuO 4 6− complexes taking into account intracenter p-d and intercenter d-d charge-transfer ͑CT͒ transitions. The band gap in the rare-earth cuprates is defined by an electric-dipole-allowed CT transitions centered at 1.54-1.59 eV in Pr, Nd, and Sm cuprates, and 2.1 eV in La cuprate. Optical response of Bi 2 CuO 4 strongly differs from the rare-earth cuprates which we relate with strong covalency of Bi-O bonding and strong ionicity of Cu͑3d͒-O͑2p͒ bonding. These features are manifested in suppression of low-energy intense intracenter p-d and intercenter d-d CT transitions, and by appearance of strong intense absorption bands near 5 eV. Regardless the strong distinctions of optical response, on one hand, of La, Pr, Nd, and Sm cuprates, and on the other hand, of the Bi cuprate, the dielectric gap in these compounds shows comparable values defined by a superposition of intracenter p-d CT transitions and two-center d-d CT transitions. Thus these cuprates should be classified as compounds intermediate between CT and Mott-Hubbard insulators.

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Anomalous optical properties of the mixed-valent lithium cuprateLiCu2O2

Cited by 22 publications

References 19 publications

Optical spectroscopy of charge transfer transitions in multiferroic manganites, ferrites, and related insulators

Optical spectroscopy of charge transfer transitions in multiferroic manganites, ferrites, and related insulators

Nonrelativistic multiferrocity in the nonstoichiometric spin-12spiral-chain cuprateLiCu2O
Moskvin¹,
Panov²,
Drechsler³
2009
Phys. Rev. B
Self Cite
33
1
28
0
View full text Add to dashboard Cite

Near-band gap electronic structure of the tetragonal rare-earth cupratesR2CuO4and the bismuth cuprateBi2
Pisarev
¹
,
Павлов
²
,
Kalashnikova
³

et al. 2010
Phys. Rev. B
Self Cite
27
0
11
0
View full text Add to dashboard Cite

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Anomalous optical properties of the mixed-valent lithium cuprateLiCu2O2

Cited by 22 publications

References 19 publications

Optical spectroscopy of charge transfer transitions in multiferroic manganites, ferrites, and related insulators

Optical spectroscopy of charge transfer transitions in multiferroic manganites, ferrites, and related insulators

Nonrelativistic multiferrocity in the nonstoichiometric spin-12spiral-chain cuprateLiCu2OMoskvin1, Panov2, Drechsler3 2009Phys. Rev. BSelf Cite331280View full textAdd to dashboardCite

Near-band gap electronic structure of the tetragonal rare-earth cupratesR2CuO4and the bismuth cuprateBi2Pisarev1, Павлов2, Kalashnikova3 et al. 2010Phys. Rev. BSelf Cite270110View full textAdd to dashboardCite

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Nonrelativistic multiferrocity in the nonstoichiometric spin-12spiral-chain cuprateLiCu2O
Moskvin¹,
Panov²,
Drechsler³
2009
Phys. Rev. B
Self Cite
33
1
28
0
View full text Add to dashboard Cite

Near-band gap electronic structure of the tetragonal rare-earth cupratesR2CuO4and the bismuth cuprateBi2
Pisarev
¹
,
Павлов
²
,
Kalashnikova
³

et al. 2010
Phys. Rev. B
Self Cite
27
0
11
0
View full text Add to dashboard Cite