Reentrant Softening in Copper-Oxide Superconductors (original) (raw)
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TMependent "Sn Mossbauer Debye-Wailer factors f(T) in EuBa2Cu2. 9sSnvm07 s display evidence of a substantial softening in lattice vibrations at T &110 K. In a previous ' 'Eu study, no detectable softemng in f(T) was found at the rare-earth site. These results taken together show that Sn atoms as a dilute impurity replace predominantly Cu(1) sites in the Cu-0 chains of the orthorhombic structure. It appears that a softening in vibrational modes localized onto the Cu-0 linear chains occurs as a precursor to the onset of superconductivity. These results show that phonons do appear to play an important role in electron pairing in these high-T, oxide superconductors.
Anomalous breaking of phonon softening in the superconducting state of La1.85Sr0.15CuO4
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Neutron inelastic scattering measurements on single crystals of La2_xSrxCuO4_y have been performed to study the relation between the soft phonon and the superconductivity. The phonon softening of the Z-point mode due to the incipient structural phase transition to the low-temperature tetragonal (P42/ncm) or orthorhombic (Pccn) phase appeared to be frozen below T c. The narrowing of the phonon line-width upon cooling was saturated below T c, suggesting the appearance of the extra line broadening in the superconducting state.
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Journal of Superconductivity and Novel Magnetism, 2012
The anomalous properties of the bond stretching (BS) phonon mode are analyzed in the underdoped region of cuprates by studying the t-t -J -Holstein model and the Hubbard-Holstein model with both numerical and analytical approaches. It is shown that a BS phonon softening occurs at an intermediate wavevector along the horizontal direction of the Brillouin zone (BZ) in agreement with recent INXS experiments as the result of the interaction among strongly correlated holes and antiferromagnetic fluctuations. An explanation of the single vs. double mode scenario is also discussed.
Superconductivity and Phonon Softening
Physical Review Letters, 1972
A new formula is derived which relates changes in electron-phonon coupling strength A, to shifts in phonon frequencies. Using this formula, the superconducting transition temperature T~is discussed for bce transition metals and rock-salt-structure transition-metal carbides. Among superconducting elements and compounds, it is common to find pairs of metals with the same crystal structure, made of elements in neighboring columns of the periodic table, in which the transition temperature T, differs greatly. Good examples are the rock-salt-structure materials HfC (with T, & 0.015'K) and TaC (with T,-11'K). Recently Smith and 615,ser' and Smith' have re