Session X12: Charge Density Wave and Charge Order

8:00 AM–10:36 AM, Friday, March 14, 2008
Morial Convention Center - 203

Sponsoring Unit: DCMP
Chair: Eduardo Fradkin, University of Illinois at Urbana-Champaign

Abstract ID: BAPS.2008.MAR.X12.3

Abstract: X12.00003 : Phonon Softening and Displacement Pattern in Commensurate Charge Density Wave in 2H-TaSe$_{2}$

8:24 AM–8:36 AM

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Authors:

  Tom Berlijn
    (Brookhaven National Laboratory)

  Wei-Guo Yin
    (Brookhaven National Laboratory)

  Wei Ku
    (Brookhaven National Laboratory)

The formation of the commensurate charge density wave (CCDW) phase of 2H-TaSe$_{2}$ is investigated via a first-principles study of the phonon spectrum. Both the linear response and the frozen phonon approach reveal strong softening of the $\Sigma_{1}$ branch at the CCDW wave vector (2$\Gamma $M/3), as observed by inelastic neutron scattering[1]. Furthermore, to resolve the disagreement between currently proposed patterns by neutron scattering[1], electron diffraction[2] and TDPAC[3], the size and the pattern of the CCDW displacement are evaluated by an $ab initio$ total energy calculation. The role of nesting and electron-phonon coupling in the miscroscopic origin of the instability will be addressed. [1] D.E. Moncton, J.D. Axe and F.J. DiSalvo, Phys. Rev. B \textbf{16}, 801 (1977), [2] D.M. Bird, S. McKernan and J.W. Steeds, J. Phys. C \textbf{18} 499 (1985), [3] T. Butz, S. Saibene and A. Lerf, J. Phys. C \textrm{19} 2675 (1986).

To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2008.MAR.X12.3