Evidence for a Singlet-Triplet Transition in Spin-Peierls System CuGe<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">O</mml:mi></mml:mrow><mml:mrow><mml:mn>3</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>

Fujita, Osamu; Akimitsu, Jun; Nishi, Masakazu; Kakurai, Kazuhisa

doi:10.1103/physrevlett.74.1677

Cited by 68 publications

(46 citation statements)

References 21 publications

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“…Inelastic neutron and light scattering experiments are very sensitive to magnetic excitations and, in the case of CuGeO 3 , they have been very powerful tools in detecting the singlet-triplet magnetic gap, 8,9 separated by a second gap from a continuum of magnon excitations, 38-41 and a singlet bound-states within the two energy gaps. 29,42 On the other hand, optical spectroscopy is usually not the elective technique to study this kind of processes, unless a static (charged magnons 43,44 ) or a dynamic (phonon assisted bi-magnons 27 ) breaking of symmetry is present in the system under investigation.…”

Section: Magnetic Excitationsmentioning

confidence: 99%

Optical spectroscopy of pure and dopedCuGeO3

et al. 2000

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We investigated in detail the optical properties of several Cu 1−δ Mg δ GeO3 (with δ = 0, 0.01), and CuGe1−xBxO3 with B=Si (x = 0, 0.007, 0.05, 0.1), and Al (x = 0, 0.01) single crystals, in the frequency range 20 -32 000 cm −1 . We report temperature dependent reflectivity and transmission measurements, performed with polarized light in order to probe the anisotropy of the crystals along the b and c axes, and optical conductivity spectra obtained by Kramers-Kronig transformation or direct inversion of the Fresnel formula. Special emphasis is given to the far-infrared phonon spectra. The temperature dependence of the phonon parameters is presented and discussed in relation to the soft mode issue in CuGeO3. For T < TSP we could detect zone boundary folded modes activated by the spin-Peierls phase transition. Following the temperature dependence of these modes, which shows the second order character of the phase transition, we were able to study the effect of doping on TSP. Moreover, in transmission experiments we detected a direct singlet-triplet excitation at 44 cm −1 , across the magnetic gap, which is not understandable on the basis of the magnetic excitation spectrum so far assumed for CuGeO3. The optical activity of this excitation and its polarization dependence confirm the existence of a second (optical) magnetic branch, recently suggested on the basis of inelastic neutron scattering data. The anisotropy in the magnetic exchange constants along the b axis, necessary for the optical triplet mode to gain a finite intensity, and the strong effect of Si substitution on the phonon spectra are discussed in relation to the alternative space group P 212121, recently proposed for CuGeO3 in the high temperature uniform phase.

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Section: Magnetic Excitationsmentioning

confidence: 99%

Optical spectroscopy of pure and dopedCuGeO3

et al. 2000

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“…Crystal structure of CuGeO 3 consists of a unique arrangement of corner-shared GeO 4 tetrahedral chains linked by an edge-sharing CuO 6 octahedral chain [2]. A large number of investigations concerned with the characterization of its structural and physical properties was done at low temperature and high pressure because of the strong correlation between structural, elastic, and magnetic properties in spin-Peierls transition system [3,4]. Evidence for the lattice dimerization, which is accompanied by the spin-Peierls transition at low temperature, was observed in electron [5], x-ray and neutron diffraction experiments [6±8].…”

Section: Introductionmentioning

confidence: 99%

Crystal Structure of the High Pressure Phase(II) in CuGeO3

Yoshiasa¹,

Yagyu²,

Ito³

et al. 2000

Z. anorg. allg. Chem.

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“…First of all, such a transition is not allowed in first-order Raman scattering due to total spin conservation. Second, we have performed corresponding experiments with magnetic fields up to 15 T. The low-energy peak does not split nor does it shift significantly below the critical field of ϳ 12.5 T, although the splitting of the triplet state was observed by inelastic neutron scattering as expected [19][20][21].…”

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Low-energy magnetic excitations in the dimerized and incommensurate phase of CuGeO3

Loa

Gronemeyer

Thomsen

et al. 1999

Solid State Communications

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Low-energy magnetic excitations in the dimerized (D) and incommensurate (I) phase of CuGeO 3 were studied by Raman spectroscopy. Based on temperature and magnetic field dependent experiments on pure and Si-doped samples the Raman peak at 17 cm Ϫ1 for T 2 K in the D-phase is attributed to a soliton-assisted one-magnon excitation. We further present a Ramanstudy of the low-energy spin dynamics of a spin-Peierls system in the incommensurate phase. The magnetic field induced transition between D-and I-phase of CuGeO 3 (B c տ 12.5 T) is characterized by the appearance of an intense new low-energy mode. For the incommensurate phase a finite zone-center excitation gap of D 2.3^0.2 cm Ϫ1 is deduced. ᭧

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Evidence for a Singlet-Triplet Transition in Spin-Peierls System CuGeO3

Cited by 68 publications

References 21 publications

Optical spectroscopy of pure and dopedCuGeO3

Optical spectroscopy of pure and dopedCuGeO3

Crystal Structure of the High Pressure Phase(II) in CuGeO3

Low-energy magnetic excitations in the dimerized and incommensurate phase of CuGeO3

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