“…Impurity substitution is also of interest in other transition metal oxides. [20][21][22][23][24][25][26][27][28][29][30] Susceptibility measurements show that CuPzN is well described by the 1-D QHAF model, where the data are fit by the Bonner Fischer model. 9, 31 The exchange constant derived from these fits is 2J/k B ) -10.4(1) K, which corresponds to a T ) 0 saturation field of 14.6 T as determined by the molecular field result for S ) 1 / 2 : gµ β H sat ) 2zk B J.…”
Section: Introductionmentioning
confidence: 99%
“…Replacing Cu 2+ ions with Zn 2+ ions breaks the linear magnetic chain. Impurity substitution is also of interest in other transition metal oxides. − 1 Crystal structure of copper pyrazine dinitrate.…”
We report the temperature-dependent infrared spectra of pure, deuterated, Zn-doped, and 2,6-dimethyl-substituted samples of the S ) 1 / 2 , one-dimensional Quantum Heisenberg Antiferromagnet (QHAF) copper pyrazine dinitrate (Cu(C 4 H 4 N 2 )(NO 3 ) 2 ). Of the more than 100 vibrational modes observed in the spectra, nearly one-third of them unexpectedly soften throughout the temperature range of investigation (300-5 K). We discuss the temperature dependence of the vibrational spectra in terms of several different models for mode softening. On the basis of detailed structural information and a comparison of the infrared spectra between pure copper pyrazine dinitrate and its chemically modified relatives, we conclude that the unusual softening observed in this low-dimensional molecular magnet is due to enhanced interchain hydrogen bonding with decreasing temperature.
“…Impurity substitution is also of interest in other transition metal oxides. [20][21][22][23][24][25][26][27][28][29][30] Susceptibility measurements show that CuPzN is well described by the 1-D QHAF model, where the data are fit by the Bonner Fischer model. 9, 31 The exchange constant derived from these fits is 2J/k B ) -10.4(1) K, which corresponds to a T ) 0 saturation field of 14.6 T as determined by the molecular field result for S ) 1 / 2 : gµ β H sat ) 2zk B J.…”
Section: Introductionmentioning
confidence: 99%
“…Replacing Cu 2+ ions with Zn 2+ ions breaks the linear magnetic chain. Impurity substitution is also of interest in other transition metal oxides. − 1 Crystal structure of copper pyrazine dinitrate.…”
We report the temperature-dependent infrared spectra of pure, deuterated, Zn-doped, and 2,6-dimethyl-substituted samples of the S ) 1 / 2 , one-dimensional Quantum Heisenberg Antiferromagnet (QHAF) copper pyrazine dinitrate (Cu(C 4 H 4 N 2 )(NO 3 ) 2 ). Of the more than 100 vibrational modes observed in the spectra, nearly one-third of them unexpectedly soften throughout the temperature range of investigation (300-5 K). We discuss the temperature dependence of the vibrational spectra in terms of several different models for mode softening. On the basis of detailed structural information and a comparison of the infrared spectra between pure copper pyrazine dinitrate and its chemically modified relatives, we conclude that the unusual softening observed in this low-dimensional molecular magnet is due to enhanced interchain hydrogen bonding with decreasing temperature.
“…In the optimally doped and overdoped regime there is substantial evidence of a nodeless order parameter, i.e. of s-wave symmetry [99][100][101]. Within our model the symmetry of the gap is independent of doping and is the same for electron-and hole-doped cuprates, namely s-wave.…”
Since their experimental discovery in 1989, the electron-doped cuprate superconductors have presented both a major challenge and a major opportunity. The major challenge has been to determine whether these materials are fundamentally different from or essentially similar to their hole-doped counterparts; a major opportunity because answering this question would strongly constrain the possible explanations for what is the essential physics that leads to high temperature superconductivity in the cuprates, which is still not agreed upon. Here we argue that experimental results over the past 30 years on electron-doped cuprate materials have provided conclusive answers to these fundamental questions, by establishing that both in hole-and electron-doped cuprates, superconductivity originates in pairing of hole carriers in the same band. We discuss a model to describe this physics that is different from the generally accepted ones, and calculate physical observables that agree with experiment, in particular tunneling characteristics. We argue that our model is simpler, more natural and more compelling than other models. Unlike other models, ours was originally proposed before rather than after many key experiments were performed. PACS numbers:
“…See also reference [10] on this. However, correcting the measured λ ab (T ) dependence for the temperature-dependent susceptibility due to the Nd 3+ moments, Alff et al still insisted on an exponential dependence indicating isotropic s-wave pairing [11]. Note that the quasiparticle tunnelling conductance spectra of NCCO closely resemble those of d-wave LSCO and YBCO [6,11].…”
Section: Introductionmentioning
confidence: 99%
“…However, correcting the measured λ ab (T ) dependence for the temperature-dependent susceptibility due to the Nd 3+ moments, Alff et al still insisted on an exponential dependence indicating isotropic s-wave pairing [11]. Note that the quasiparticle tunnelling conductance spectra of NCCO closely resemble those of d-wave LSCO and YBCO [6,11]. Pair tunnelling measurements indicate the product of the critical current and the junction normal-state resistance (I c R N ) to lie between 0.5 and 6 µV for Pb/NCCO c-axisoriented films and single crystals [12]-almost three orders of magnitude smaller than the 3 mV Ambegaokar-Baratoff limit expected for an s-wave superconductor.…”
Taking the two-local-spin-mediated interaction as a Cooper pair interaction, using the BCS (Bardeen-Cooper-Schrieffer) gap equation and the phase-coherence condition for quantum phase fluctuation, this paper explains basic experimental findings concerning both ptype La 2−x Sr x CuO 4 (LSCO) and n-type Nd 2−x Ce x CuO 4 (NCCO) at the same time, and predicts that the pseudogap should be clearly observed for underdoped NCCO.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
