Friday, 10 May 2013

Phonon Energy Gaps in the Charged Incommensurate Planes of the Spin-Ladder Sr14Cu24O41 Compound by Raman and Infrared Spectroscopy (FULL TEXT)

Physical Review Letters 108, 217401 (2012)
© 2012 American Physical Society
url: http://link.aps.org/doi/10.1103/PhysRevLett.108.217401
doi: 10.1103/PhysRevLett.108.217401
PACS:  78.30.-j, 71.45.Lr, 78.70.Gq

Authors: V. K. Thorsmølle1,2,4,*, C. C. Homes3,†, A. Gozar3,‡, G. Blumberg4, J. L. M. van Mechelen2, A. B. Kuzmenko2, S. Vanishri5, C. Marin5, and H. M. Rønnow6
1 Laboratory for Photonics and Interfaces, École Polytechnique Fédérale de Lausanne (EPFL), CH-1015, Switzerland2 Département de Physique de la Matière Condensée, Université de Genève, CH-1211 Genève 4, Switzerland3 Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, New York 11973, USA4 Department of Physics and Astronomy, Rutgers, The State University of New Jersey, Piscataway, New Jersey 08854, USA5 CEA Grenoble, INAC, SPSMS, IMAPEC, 17 rue des Martyrs, 38054 Grenoble, France6Laboratory for Quantum Magnetism, École Polytechnique Fédérale de Lausanne (EPFL), CH-1015, Switzerland

Abstract

The terahertz (THz) excitations in the quantum spin-ladder system Sr14Cu24O41 have been determined along the c axis using THz time-domain, Raman, and infrared spectroscopy. Low-frequency infrared and Raman active modes are observed above and below the charge-ordering temperature Tco≃200  K over a narrow interval ≃1–2  meV (≃8–16  cm-1). A new infrared mode at ≃1  meV develops below ≃100  K. The temperature dependence of these modes shows that they are coupled to the charge- and spin-density-wave correlations in this system. These low-energy features are conjectured to originate in the gapped sliding motion of the chain and ladder subsystems, which are both incommensurate and charged.

...The THz-TDS experiments (TPI spectra 1000, TeraView Ltd.) were performed in transmission geometry with the sample mounted inside an optical cryostat capable of reaching 5 K...

Full text available at:
http://girsh.rutgers.edu/Papers/Verner_PhysRevLett.108.217401.pdf