Berlin 2012 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 19: Correlated Electrons: (General) Theory 2

TT 19.12: Vortrag

Dienstag, 27. März 2012, 12:45–13:00, H 3010

Temperature evolution of phonon spectra of elemental iron near the α-γ phase transition — •I. Leonov¹, A. I. Poteryaev^2,3, V. I. Anisimov², and D. Vollhardt¹ — ¹TP III, Center for Electronic Correlations and Magnetism, Uni Augsburg, Germany — ²Institute of Metal Physics, Yekaterinburg, Russia — ³Institute of Quantum Materials Science, Yekaterinburg, Russia

We present results of a theoretical investigation of the electronic and lattice dynamical properties of elemental iron at finite temperatures obtained within dynamical mean-field theory implemented with the frozen-phonon method [1]. This approach allows us to compute correlation induced lattice transformations and their temperature evolution. We find that electronic correlations are important to explain the lattice stability of iron at the bcc-fcc phase transition. We notice a weak anomaly in the transverse T₁ acoustic mode in the Γ-N direction of the bcc phase. This behavior can be ascribed to a dynamical precursor effect of the bcc-to-fcc phase transition and is found to occur above the Curie temperature. Upon further heating, the bcc phase becomes dynamically unstable due to the T₁ mode near the N point. By contrast, the fcc lattice is found to be dynamically stable in a broad temperature range, including temperatures above and below the bcc-fcc phase transition temperature. Our results for the structural phase stability and lattice dynamical properties of iron are in good agreement with experiment.
I. Leonov et al., Phys. Rev. Lett. 106, 106405 (2011); I. Leonov et al., arXiv:1110.0439 (2011).