title: Phonon energy gaps in the charged incommensurate planes of the spin-ladder Sr14Cu24O41 compound by Raman and infrared spectroscopy.
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 T(co) is approximately equal to 200 K over a narrow interval approximately equal to 1-2 meV approximately equal to 8-16 cm(-1)). A new infrared mode at approximately equal to 1 meV develops below approximately equal to 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.
authors.affiliation: Laboratory for Photonics and Interfaces, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland. vernerkt@physics.rutgers.edu
authors.forename: V K
authors.initials: VK
authors.lastname: Thorsmølle
authors.forename: C C
authors.initials: CC
authors.lastname: Homes
authors.forename: A
authors.initials: A
authors.lastname: Gozar
authors.forename: G
authors.initials: G
authors.lastname: Blumberg
authors.forename: J L M
authors.initials: JL
authors.lastname: van Mechelen
authors.forename: A B
authors.initials: AB
authors.lastname: Kuzmenko
authors.forename: S
authors.initials: S
authors.lastname: Vanishri
authors.forename: C
authors.initials: C
authors.lastname: Marin
authors.forename: H M
authors.initials: HM
authors.lastname: Rønnow