1,059 research outputs found
Dispersion Anomalies in Cuprate Superconductors
We argue that the shape of the dispersion along the nodal and antinodal
directions in the cuprates can be understood as a consequence of the
interaction of the electrons with collective spin excitations. In the normal
state, the dispersion displays a crossover at an energy where the decay into
spin fluctuations becomes relevant. In the superconducting state, the antinodal
dispersion is strongly affected by the spin resonance and displays an S-shape
whose magnitude scales with the resonance intensity. For nodal fermions,
relevant spin excitations do not have resonance behavior, rather they are
better characterized as a gapped continuum. As a consequence, the S-shape
becomes a kink, and superconductivity does not affect the dispersion as
strongly. Finally, we note that optical phonons typically lead to a temperature
independent S-shape, in disagreement with the observed dispersion.Comment: 12 pages, 7 eps figure
Luttinger theorem for a spin-density-wave state
We obtained the analog of the Luttinger relation for a commensurate
spin-density-wave state. We show that while the relation between the area of
the occupied states and the density of particles gets modified in a simple and
predictable way when the system becomes ordered, a perturbative consideration
of the Luttinger theorem does not work due to the presence of an anomaly
similar to the chiral anomaly in quantum electrodynamics.Comment: 4 pages, RevTeX, 1 figure embedded in the text, ps-file is also
available at http://lifshitz.physics.wisc.edu/www/morr/morr_homepage.htm
Spin-liquid model of the sharp resistivity drop in
We use the phenomenological model proposed in our previous paper [Phys. Rev.
Lett. {\bf 98}, 237001 (2007)] to analyse the magnetic field dependence of the
onset temperature for two-dimensional fluctuating superconductivity . We demonstrate that the slope of progressively goes down as
increases, such that the upper critical field progressively increases as
decreases. The quantitative agreement with the recent measurements of
in is achieved for the same parameter
value as was derived in our previous publication from the analysis of the
electron self energy.Comment: 4 pages, 2 figure
Signatures of non-monotonic d-wave gap in electron-doped cuprates
We address the issue whether the data on optical conductivity and Raman
scattering in electron-doped cuprates below support the idea that the
wave gap in these materials is non-monotonic along the Fermi surface. We
calculate the conductivity and Raman intensity for elastic scattering, and find
that a non-monotonic gap gives rise to several specific features in optical and
Raman response functions. We argue that all these features are present in the
experimental data on NdCeCuO and PrCeCuO
compounds.Comment: 7 pages, 6 figure
Non-fermi liquid behavior in itinerant antiferromagnets
We consider a two dimensional itinerant antiferromagnet near a quantum
critical point. We show that, contrary to conventional wisdom, fermionic
excitations in the ordered state are not the usual Fermi liquid quasiparticles.
Instead, down to very low frequencies, the fermionic self energy varies as
. This non-Fermi liquid behavior originates in the coupling of
fermions to the longitudinal spin susceptibility
in which the order-induced ``gap'' in the spectrum at dissolves into the
Landau damping term at . The transverse spin fluctuations obey
scaling characteristic of spin waves, but remain overdamped in a finite
range near the critical point.Comment: 5p., 3fig
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