Phonon anomalies and electron-phonon interaction in theRuSr2GdCu2O

Abstract

Critical behavior of the infrared reflectivity of RuSr2GdCu2O8 ceramics is observed near the superconducting TSC = 45 K and magnetic TM = 133 K transition temperatures. The optical conductivity reveals the typical features of the c-axis optical conductivity of strongly underdoped multilayer superconducting cuprates. The transformation of the Cu-O bending mode at 288 cm −1 to a broad absorption peak at the temperatures between T * = 90 K and TSC is clearly observed, and is accompanied by the suppression of spectral weight at low frequencies. The correlated shifts to lower frequencies of the Ru-related phonon mode at 190 cm −1 and the mid-IR band at 4800 cm −1 on decreasing temperature below TM are observed. It provides experimental evidence in favor of strong electron-phonon coupling of the charge carriers in the Ru-O layers which critically depends on the Ru core spin alignment. The underdoped character of the superconductor is explained by strong hole depletion of the CuO2 planes caused by the charge carrier self-trapping at the Ru moments.

Correlation between the Josephson coupling energy and the condensation energy in bilayer cuprate superconductors

“…Although the anomalies start to develop above T c in strongly underdoped compounds, the pronounced and steep changes always occur right at T c [17]. Similar though less spectacular effects have also been observed for other values of δ [14,15,16,17,18,19,34], for several other bilayer compounds [35,36,37,38,39], and for the trilayer compound Tl 2 Ba 2 Ca 2 Cu 3 O 10 [40]. Also shown in Fig.…”

Carrier dynamics and infrared-active phonons in c-axis oriented RuSr2GdCu2O8 film

“…The fact of strongly overdamped carrier dynamics is reflected in almost constant in-plane "background" conductivity in the frequency range below 800 cm −1 . We mention that the absolute values of conductivity are by factor of two higher compared to what was earlier reported for ceramic Ru1212 samples, 14,15 for which the in-plane conductivity was supposed to be a dominant component. 16 The four peaks are the most intensive phonons.…”

Structural, transport, and magnetic properties of pure and La-dopedRuSr2GdCu2OMandal1, Hassen2, Krimmel3 et al. 2002Phys. Rev. BSelf Cite327200View full textAdd to dashboardCite

“…For the isostructural Eu compound these transition temperatures are shifted to 32 K and 132 K respectively 6,7 . The intrinsic nature of bulk superconductivity and the uniform character of the magnetic interactions have been shown utilizing muon-spin rotation 3 , ESR techniques 8 , Raman 9 , and FIR experiments 10 .…”