Sep 12 – 17, 2010
Europe/Zurich timezone
The conference is now over. Thanks to all for their participation. <p> The talks from the various sessions are all online.

Density of Phonon States at the Fe Sites in Superconducting FeSe as Function of Temperature and Pressure

Sep 15, 2010, 12:10 PM
500/1-001 - Main Auditorium (CERN)

500/1-001 - Main Auditorium


Show room on map


Prof. Gerhard Wortmann (2Department Physik, Universität Paderborn)


The temperature and pressure dependence of the partial density-of-phonon states (phonon-DOS) at the iron sites in superconducting (sc) Fe1.01Se was studied by 57Fe nuclear inelastic scattering (NIS) of synchrotron radiation, a method well adapted for these studies as function of temperature and pressure [1,2]. As proved by a recent study of the isotope effect at the Fe sites on the sc temperature Tc in FeSe, superconductivity is intrinsically connected with the Fe phonon modes [3]. The sc properties of the present Fe1.01Se sample and their pressure dependencies were well characterized in previous studies using various methods, including 57Fe-Mössbauer spectroscopy [4-7]. The high energy resolution in the present 57Fe-NIS study allows for a detailed observation of spectral properties in the phonon-DOS not observed before, e.g. shifts of all spectral features to higher energies by ~4% with decreasing temperature from 296 K to 10 K. No detectable changes in the partial Fe phonon-DOS were observed at the tetragonal–orthorhombic transition around 100 K [7,8]. An applied pressure of 6.7 GPa, combined with an increase of the sc temperature Tc from 8 K to 34 K [8], resulted in an increase of the optical phonon-mode energies by ~12%, and an even more pronounced increase in energies of the lowest-lying transversal acoustic modes. Despite of these strong pressure-induced changes in the partial Fe phonon-DOS we conclude that the pronounced increase of Tc in Fe1.01Se with pressure cannot be described in the framework of classical electron-phonon coupling [8]. This suggests the importance of spin fluctuations for the observed superconductivity [9]. The present results are discussed in conjunction with the phonon-DOS of FeSe0.5Te0.5 X-tals, studied including its polarization dependence by 57Fe-NIS [10], where Tc = 15 K was observed at ambient pressure. Finally we present a synopsis of the complementary information on the sc Fe1.01Se and FeSe0.5Te0.5 systems, obtained from the elastic channel, 57Fe-ME [4-7], as well as from the inelastic channel, 57Fe-NIS [8, 10], of the 57Fe(14.4 keV)-Mössbauer resonance. References: * [1] A.I. Chumakov et al., Phys. Rev. B 54, R9596 (1996). [2] R. Lübbers, H.F. Grünsteudel, A.I. Chumakov, G. Wortmann, Science 287, 1250 (2000). [3] R. Khasanov et al., arXiv:1002.2510.v1. [4] T.M. McQueen et al., Phys. Rev. B 79, 014522 (2009). [5] S. Medvedev et al., Nature Mater. 8, 630 (2009). [6] V. Ksenofontov et al., contribution to this conference. [7] T.M. McQueen et al., Phys. Rev. Lett. 103, 057002 (2009). [8] V. Ksenofontov et al., Phys. Rev. B (in print); see arXiv:1004.2007. [9] T. Imai et al., Phys. Rev. Lett. 102, 177005 (2009). [10] V. Ksenofontov, G. Wortmann, T. Gasi, J. Deisenhofer, V. Tsurkan, C. Felser (unpublished)
Are you a student, a delegate from developing countries or a participant with physical needs and would like to apply for a sponsored accomodation. Please answer with yes or no. no
Please specify whether you would prefer an oral or poster contribution. oral

Primary author

Prof. Gerhard Wortmann (2Department Physik, Universität Paderborn)


A.I. Chumakov3 (European Synchrotron Radiation Facility) C Felser (Institut Anorg. Analyt. Chemie, Universität Mainz) R. J. Cava (Department of Chemistry, Princeton University) S Medvedev (Institut Anorg. Analyt. Chemie, Universität Mainz) T Gasi (Institut Anorg. Analyt. Chemie, Universität Mainz) T. M. McQueen (Department of Chemistry, Princeton University) V Ksenofontov (Institut Anorg. Analyt. Chemie, Universität Mainz)

Presentation materials