Quantum Critical Behavior of Clean Itinerant Ferromagnets
We consider the quantum ferromagnetic transition at zero temperature in clean itinerant electron systems. We find that the Landau-Ginzburg-Wilson order parameter field theory breaks down since the electron-electron interaction leads to singular coupling constants in the Landau-Ginzburg-Wilson functional. These couplings generate an effective long-range interaction between the spin or order parameter fluctuations of the form 1/r2d-1, with d the spatial dimension. This leads to unusual scaling behavior at the quantum critical point in 1 < d ≤ 3, which we determine exactly. We also discuss the quantum-to-classical crossover at small but finite temperatures, which is characterized by the appearance of multiple temperature scales. A comparison with recent results on disordered itinerant ferromagnets is given.
T. Vojta et al., "Quantum Critical Behavior of Clean Itinerant Ferromagnets," Zeitschrift fur Physik B-Condensed Matter, vol. 103, no. 3-4, pp. 451-461, Springer Verlag, Apr 1997.
The definitive version is available at http://dx.doi.org/10.1007/s002570050399
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