Optical Study on Phonon Anomalies and Spin Gap inYBa2(Cu1−x

Abstract

Optical reflectivity measurements with E k c on YBa 2 ͑Cu 12x Zn x ͒ 3 O 6.6 reveal a dramatic Znsubstitution effect on the anomaly of the in-plane oxygen bending mode and the broad absorption band around 450 cm 21 which are observed at low temperatures for x 0, whereas the low-v suppression of the optical conductivity remains unchanged. This indicates a close relation between the phonon anomaly and the absorption band, while the conductivity suppression is an independent phenomenon. The former suggests a coupling of the phonons to spin fluctuations at ͑p, p͒, leading to anomalous spectral behavior when a spin gap opens. [S0031-9007(96)01777-2] PACS numbers: 74.25. Gz, 63.20.Kr, 74.72.Bk, 78.30.Er Many of the anomalous properties in the normal state of high-T c superconductors (HTSC) have been discussed in connection with a strong electron correlation and/ or spin fluctuations. Particularly, the so-called "spin gap" phenomenon, observed in the spin-lattice relaxation rate T 21

Phonon anomalies and electron-phonon interaction in theRuSr2GdCu2OBoris1, Mandal2, Bernhard3 et al. 2001Phys. Rev. B24382View full textAdd to dashboardCite

“…This behavior involving an anomaly of the Cu-O bending mode, accompanied by the formation of an additional broad absorption band at phonon frequencies, is well studied in the c-axis IR-conductivity of underdoped layered cuprates. 10,11,18,19 The mechanism of this phenomenon is a subject of ongoing discussions. [8][9][10]19 The most favored explanation is based on a model where the bilayer cuprate compounds are treated as a superlattice of inter-and intrabilayer Josephson junctions.…”

“…10,11,18,19 The mechanism of this phenomenon is a subject of ongoing discussions. [8][9][10]19 The most favored explanation is based on a model where the bilayer cuprate compounds are treated as a superlattice of inter-and intrabilayer Josephson junctions. 8,10,11 In this model the additional absorption peak is related to the transverse bilayer plasmon, while the anomalous softening and the loss of the spectral weight of the Cu-O bending mode are explained to be due to the drastic changes of the local electrical fields acting on the in-plane oxygen ions as the Josephson current sets in.…”

New Josephson Plasma Modes in UnderdopedYBa2Cu3O6.6Kojima1, Uchida2, Fudamoto3 et al. 2002Phys. Rev. Lett.Self Cite323300View full textAdd to dashboardCite

“…Observations of a broad peak at ∼ 400cm −1 in the optical conductivity which appears below the pseudo-gap temperature have been made by several groups [8,9,10,11,12]. This "400cm −1 " peak has been interpreted as the out-of-phase coupling of the two types of Josephson junctions in YBCO, which correspond to the intra-and the inter-bilayer coupling [17,18].…”

“…Depending on the anisotropy parameter γ = λ c /λ ab , the Josephson plasma frequency ranges from the microwave (γ ∼ 300 − 1000 for Bi 2 Sr 2 CaCu 2 O 8+δ (Bi-2212) [5,6,7]) to the far infrared frequency (γ ∼ 50 for underdoped YBCO [8,9,10,11,12] and La 2−x Sr x CuO 4 (LSCO) [1,13]). The optical/microwave response originates from the restoration of coherent transport due to the tunneling of superconducting carriers between the CuO 2 layers.…”

Pseudogap Study Usingc-axis Optical Spectra of Underdoped YBa2Cu3O7-δ

“…For the pseudogap state, the lost spectral weight with suppression is transferred to the higher energy region, while in the superconducting condensation case, it is redistributed as a delta function at ω = 0. It has been shown that the superconducting condensation can be suppressed with Zn-doping [2] that makes easy to observe the features due to the pseudogap.…”