Anomalous Lattice Dynamics of ${\mathrm{EuSi}}_{2}$ Nanoislands: Role of Interfaces Unveiled

Anomalous Lattice Dynamics of ${EuSi}_{2}$ Nanoislands: Role of Interfaces Unveiled

A. Seiler, P. Piekarz, S. Ibrahimkutty, D. G. Merkel, O. Waller, R. Pradip, A. I. Chumakov, R. Rüffer, T. Baumbach, K. Parlinski, M. Fiederle, and S. Stankov

Phys. Rev. Lett. 117, 276101 – Published 28 December 2016

Abstract

We report a systematic lattice dynamics study of ${EuSi}_{2}$ films and nanoislands by in situ nuclear inelastic scattering on ${}^{151}{Eu}$ and ab initio theory. The Eu-partial phonon density of states of the nanoislands exhibits anomalous excess of phonon states at low and high energies, not present in the bulk and at the ${EuSi}_{2} (001)$ surface. We demonstrate that atomic vibrations along the island-substrate interface give rise to phonon states both at low and high energies, while atomic vibrations across the island-island interface result in localized high-energy phonon modes.

Received 27 July 2016

DOI:https://doi.org/10.1103/PhysRevLett.117.276101

Physics Subject Headings (PhySH)

Anharmonic lattice dynamics Interface & surface thermodynamics

Rare-earth alloys Solid-solid interfaces Surfaces

Density functional theory Gamma ray spectroscopy Molecular beam epitaxy

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

A. Seiler^1,2, P. Piekarz³, S. Ibrahimkutty^1,2,†, D. G. Merkel^4,‡, O. Waller^1,2,§, R. Pradip^1,2, A. I. Chumakov⁴, R. Rüffer⁴, T. Baumbach^1,2,5, K. Parlinski³, M. Fiederle⁶, and S. Stankov^2,1,*

¹Laboratory for Applications of Synchrotron Radiation, Karlsruhe Institute of Technology, D-76131 Karlsruhe, Germany
²Institute for Photon Science and Synchrotron Radiation, Karlsruhe Institute of Technology, D-76344 Eggenstein-Leopoldshafen, Germany
³Institute of Nuclear Physics, Polish Academy of Sciences, PL-31342 Kraków, Poland
⁴ESRF-The European Synchrotron, F-38000 Grenoble, France
⁵ANKA Synchrotron Radiation Facility, Karlsruhe Institute of Technology, D-76344 Eggenstein-Leopoldshafen, Germany
⁶Freiburg Materials Research Center, University of Freiburg, D-79104 Freiburg, Germany

^*Corresponding author. Svetoslav.Stankov@kit.edu
^†Present address: Max Planck Institute for Solid State Research, D-70569 Stuttgart, Germany.
^‡On leave from Institute for Particle and Nuclear Physics, Wigner Research Centre for Physics, Hungarian Academy of Sciences, H-1525 Budapest, Hungary.
^§Present address: Polytechnique Montréal, Montréal, Québec H3C 3A7, Canada.