Topic
Nuclear quadrupole resonance
About: Nuclear quadrupole resonance is a research topic. Over the lifetime, 3531 publications have been published within this topic receiving 38801 citations. The topic is also known as: Nuclear quadrupole resonance spectroscopy & NQR.
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TL;DR: In this article, the authors measured the frequencies νQ, the linewidth and the spin-lattice and spin-spin relaxation times T1 and T2, respectively, of the 63Cu NQR signals for chain and planar copper sites in YBa2Cu4O8 were measured between 6 and 750 K; in addition nuclear magnetic resonance (NMR) spectra were taken at 150 and 300 K.
Abstract: The frequencies νQ, the linewidth and the spin-lattice and spin-spin relaxation times T1 and T2, respectively, of the 63Cu nuclear quadrupole resonance (NQR) signals for chain and planar copper sites in YBa2Cu4O8 were measured between 6 and 750 K; in addition nuclear magnetic resonance (NMR) spectra were taken at 150 and 300 K. The results are compared with data known for the related structure YBa2Cu3O7. Above Tc the tensors of the electric field gradient and the anisotropic Knight shift at the copper sites differ in a subtle way from those of YBa2Cu3O7. At the Cu2 site, the derivative of νQ with respect to temperature changes its sign around 200 K. No indication for magnetic ordering at the Cu sites was found. Below Tc there is no evidence for BCS type relaxation and the Cu2 Tc rates vary like exp( T T 0 ) and the Cu1 rates like Tn with n≈1.35. Above Tc the Cu1 rates suggest the presence of quasiparticles (and phonon interactions) while the Cu2 rates can perhaps be explained by a model of Monien et al. postulating the coupling of Cu nuclei to itinerant interacting quasiparticles.
106 citations
TL;DR: In this article, the hole number in the Cu-3 d x 2 - y 2 orbit was found to be more than 0.85 in La 2-x Sr x CuO 4 ( x = 0.075∼0.24), while decreases to 0.74 in Tl 2 Ba 2 Ca 2 Cu 3 O 10.
Abstract: The hole numbers at Cu and oxygen sites in the CuO 2 plane in a wide variety of high- T c materials have been extracted from the measured nuclear quadrupole frequency, ν Q . The hole number in the Cu-3 d x 2 - y 2 orbit, n x 2 - y 2 , is found to be more than 0.85 in La 2- x Sr x CuO 4 ( x =0.075∼0.24), while decreases to 0.74 in Tl 2 Ba 2 Ca 2 Cu 3 O 10 . Thus estimated n x 2 - y 2 is supported by the result that the orbital Knight shift along the c -axis, K c o r b , increases in proportion to n x 2 - y 2 . In contrast to the decrease of n x 2 - y 2 , the hole number in the O-2 p σ orbit, n p σ , increases in going from the La- to the Tl-systems. It has been found that T c is determined by two parameters about holes, i.e., n x 2 - y 2 +2 n p σ and n x 2 - y 2 /2 n p σ . The former tells the microscopic \lq\lqdoping level” of the CuO 2 plane, while a smaller n x 2 - y 2 /2 n p σ results in a weaker antiferromagnetic spin fluctuations of low energy. It has been found that not only a proper n x 2 - y 2 +2 ...
106 citations
TL;DR: It is found that (101)K(c) is invariant with respect to the field and temperature on passing through H(c2) and T(c), which indicates that the spin susceptibility along the c axis does not change in the SC state, at least, in the field greater than 200 Oe.
Abstract: 101Ru-Knight shift (101K) in the spin-triplet superconductor Sr2RuO4 was measured under magnetic fields parallel to the c axis (perpendicular to the RuO2 plane), which is the promising superconducting (SC) d-vector direction in a zero field. We succeeded in measuring K(c) in the field range from 200 to 1200 Oe and at temperatures down to 80 mK, using nuclear-quadrupole-resonance spectra. We found that (101)K(c) is invariant with respect to the field and temperature on passing through H(c2) and T(c) above 200 Oe. This indicates that the spin susceptibility along the c axis does not change in the SC state, at least, in the field greater than 200 Oe. The results imply that the SC d vector is in the RuO2 plane when the magnetic field is applied to the c axis.
106 citations
TL;DR: The non-Abelian gauge structure associated with nuclear quadrupole resonance with Abelian part has been experimentally observed and the phases to be observed in various non- Abelian experiments are computed.
Abstract: We elucidate the non-Abelian gauge structure associated with nuclear quadrupole resonance. The Abelian part of this structure has been experimentally observed. The phases to be observed in various non-Abelian experiments are computed.
104 citations