Dresden 2017 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 61: Correlated Electrons: (General) Theory 2
TT 61.8: Talk
Thursday, March 23, 2017, 11:30–11:45, HSZ 204
The role of fluctuations for density-wave instabilities — •Mareike Hoyer1,2, Sonja Fischer3,1, and Jörg Schmalian1,2 — 1Institut für Theorie der Kondensierten Materie, Karlsruher Institut für Technologie, Deutschland — 2Institut für Festkörperphysik, Karlsruher Institut für Technologie, Deutschland — 3Institute for Theoretical Physics, Universiteit Utrecht, Niederlande
Density-wave instabilities have been observed and studied in a multitude of materials. In particular, in the context of unconventional superconductors like the iron-based superconductors, they have excited considerable interest, since they compete with the superconducting state in these materials. We analyze the fluctuation corrections to the equation of state of the density-wave order parameter for commensurate charge and spin-density waves due to perfect nesting. For XY magnets, we find that contributions due to longitudinal and transverse fluctuations cancel each other, making the mean-field analysis of the problem controlled. This is consistent with the observation by Kos, Millis, and Larkin [1], who analyzed fluctuation corrections to the BCS theory of superconductivity. However, in case of charge-density waves and spin-density waves with Heisenberg symmetry, we find that fluctuation corrections are not negligible, and hence mean-field theories are not justified. These singular fluctuations originate from the intermediate length-scale regime, with wavelengths between the lattice constant and the T=0 correlation length. We comment on strategies to resolve this challenge in the description of density-wave instabilities.
[1] Š. Kos, A. J. Millis, and A. I. Larkin, PRB 70, 214531 (2004)