10,325 research outputs found
Electronic Transport at Low Temperatures: Diagrammatic Approach
We prove that a diagrammatic evaluation of the Kubo formula for the
electronic transport conductivity due the exchange of bosonic excitations, in
the usual conserving ladder approximation, yields a result consistent with the
Boltzmann equation. In particular, we show that an uncontrolled approximation
that has been used to solve the integral equation for the vertex function is
unnecessary. An exact solution of the integral equation yields the same
asymptotic low-temperature behavior as the approximate one, albeit with a
different prefactor, and agrees with the temperature dependence of the
Boltzmann solution. Examples considered are electron scattering from acoustic
phonons, and from helimagnons in helimagnets.Comment: Submitted to Physics E (FMQT08 Proceedings). Requires Elsevier style
file (included
Quantum ferromagnetic transition in disordered itinerant electron systems
An effective field theory is derived for the ferromagnetic transition of
diffusive electrons at T=0. The static disorder which leads to diffusive
electron dynamics induces an effective long-range interaction between the spins
of the form 1/r^(2d-2). This leads to unusual scaling behavior at the quantum
critical point, which is determined exactly. The crossover from this quantum
fixed point to the classical Heisenberg fixed point should be observable in
ferromagnetic materials with low Curie temperatures.Comment: 4pp, REVTeX, no figs, final version as publishe
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