####################################################
# Yen-Ru Lee <junolee@uiuc.edu>
# requesting 8 days, at minimum=6 days
# beamline 33BM, phonon dispersions in CDW material : 2H-NbSe2 by x-ray thermal difuse scattering
# instrument 33BM-C fourc
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# top:/home/www/beamtime-requests/req00697.txt
# UNICAT Member Beam Time Request  #697
# created Sun Dec 05 01:38:07 CST 2004
####################################################

apsrun:
	2005-01

beamline:
	33BM

collaboration:
	No

collaborator_Hawoong:
	ON

contact:
	junolee@uiuc.edu

days:
	8

description:
	Due to electron-phonon interaction, the phase with uniform charge distribution is unstable toward the formation of charge density wave (CDW) at low temperatures. It is know that the 2H-NbSe2 undergoes a phase transition to CDW at Tp=33.5K. The transition appears to be second-order and involve atomic displacements of Sigma-1 symmetry; this phonon branch is of key importance in the CDW transition and formation. By using the temperature dependent x-ray thermal diffuse scattering technique, the phonon dispersion relations along [z 0 0] and [z 0 ½] can be revealed. Besides, Even 2H-NbSe2 undergoes a phase transition of superconductor at Tc=7.2K, the NbSe2 superlattice remains incommensurate to 5k. That might be interesting to reveal the CDW formation and related phonon dispersion near Tc by TDS technique.

equipment_required:
	cryostats,superconducting magnets,Roper CCD, Mar 345

experiment:
	phonon dispersions in CDW material : 2H-NbSe2 by x-ray thermal difuse scattering

foreign_nationals:
	Chao-Hung Du

hazards:
	

instrument:
	33BM-C fourc

instrument_other:
	

minimumdays:
	6

name:
	Yen-Ru Lee

new_request:
	ON

nonmembers:
	

unacceptable_dates:
	March 21-25, 2005
Feb. 8-12, 2005

z34ID_details:
	


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