11,997 research outputs found
Anomalous Chiral Action from the Path-Integral
By generalizing the Fujikawa approach, we show in the path-integral
formalism: (1) how the infinitesimal variation of the fermion measure can be
integrated to obtain the full anomalous chiral action; (2) how the action
derived in this way can be identified as the Chern-Simons term in five
dimensions, if the anomaly is consistent; (3) how the regularization can be
carried out, so as to lead to the consistent anomaly and not to the covariant
anomaly. Our method uses Schwinger's ``proper-time'' representation of the
Green's function and the gauge invariant point-splitting technique. We find
that the consistency requirement and the point-splitting technique allow both
an anomalous and a non-anomalous action. In the end, the nature of the vacuum
determines whether we have an anomalous theory, or, a non-anomalous theoryComment: 28 page
Frustration of square cupola in Sr(TiO)Cu(PO)
The structural and magnetic properties of the square-cupola antiferromagnet
Sr(TiO)Cu(PO) are investigated via x-ray diffraction,
magnetization, heat capacity, and P nuclear magnetic resonance
experiments on polycrystalline samples, as well as density-functional
band-structure calculations. The temperature-dependent unit cell volume could
be described well using the Debye approximation with the Debye temperature of
550~K. Magnetic response reveals a pronounced
two-dimensionality with a magnetic long-range-order below ~K. High-field magnetization exhibits a kink at of the saturation
magnetization. Asymmetric P NMR spectra clearly suggest strong in-plane
anisotropy in the magnetic susceptibility, as anticipated from the crystal
structure. From the P NMR shift vs bulk susceptibility plot, the
isotropic and axial parts of the hyperfine coupling between P nuclei and
the Cu spins are calculated to be and
~Oe/, respectively. The
low-temperature and low-field P NMR spectra indicate a commensurate
antiferromagnetic ordering. Frustrated nature of the compound is inferred from
the temperature-dependent P NMR spin-lattice relaxation rate and
confirmed by our microscopic analysis that reveals strong frustration of the
square cupola by next-nearest-neighbor exchange couplings.Comment: 11 pages, 13 figures, 1 table, Phys. Rev. B (Accepted, 2018
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