Raman Scattering From the Superconductor Niobium-Diselenide

At 33 K 2H-NbSe(,2) distorts into an incommensurate charge density wave (CDW) state. The Raman spectrum shows amplitude modes of A and E symmetry near 40 cm('-1) induced by the CDW. At 7 K this material becomes superconducting, and at 2 K we observe additional Raman peaks near 20 cm('-1), one each of A and E symmetry. These are close in energy to the energy gap 2(DELTA), as measured by far infrared transmission. The Raman activity of the gap excitations is believed to be caused by coupling to the Raman active CDW phonon modes. Such coupling is shown directly by the changes in the Raman spectra at 2 K due to an applied magnetic field. The zero field results can be explained by a model (by C. A. Balseiro and L. M. Falicov) in which the optical CDW phonon modes couple to superconducting electrons, and the resulting phonon self energy is calculated using the BCS theory for the electrons.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Physics

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2015

Author dc:creator

• Sooryakumar, Ratnasingham

• Physics, Condensed Matter

Language dc:language

eng

Identifier

(UMI)AAI8108670

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/77197