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# Eric D. Isaacs <isaacs@Lucent.com>
# requesting 5 days, at minimum=3 days
# beamline 33BM, "Search for Charge ordering in Untwinned LSCO"
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# top:/home/www/beamtime-requests/req00360.txt
# UNICAT Member Beam Time Request  #360
# created Mon Jan 13 09:09:53 CST 2003
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beamline:
	33BM

collaboration:
	Yes

collaborator+Paul:
	on

contact:
	isaacs@Lucent.com

days:
	5

description:
	The competition between the insulating states and superconductivity
	is a key feature of the high-TC problem, yet the character of the 
	insulating state remains elusive.  Striped density waves are one 
	of the primary candidates for the insulating ground state.  However, 
	direct and unambiguous x-ray observation of any charge ordered state 
	in the cuprates remains an outstanding problem in the high-TC 
	community.  In the past year, quasi-elastic Raman scattering data 
	published in Science has provided some of the most compelling 
	evidence for a pinned density wave in the quasi one-dimensional 
	ladder compound Sr14Cu24O41.  Very recently, unpublished results 
	have shown a similar fingerprint of pinned charge density waves 
	in the world's first untwined crystals of La2-xSrxCuO4. The keys 
	to this finding, were the very low doping (x~0.01) and the fact 
	that these samples were untwined.
	    This past December we began the search for charge ordering in LSCO
	with 1% Sr at 20 K at 33BM.  Measurements made in the [hk0]-plane, 
	and just above and below this plane with delL=+/-0.1, showed evidence
	for two sets of two-fold peaks.  The rectangular pattern indicates an
	anisotropic ordering of the doped holes.  We propose making a similar
	set of x-ray measurements in an untwinned sample with 3% Sr.  This will 
	allow us to observe systematic variations in the pattern which would
	be important confirmaiton of the charge ordered state.  A particular
	challenge is seperating out the scattering from the holes at very 
	incommesurate positions and that due to the tails of the very bright
	(2,4,0) Bragg peak.  We also plan to reorient the new samples with
	a* perpendicular to the surface.  This will ensure that our highest
	resolution will be along the direction of the largest incommensurability
	as observed in measurements from the Fall.

equipment+required:
	displex w/Be dome

experiment:
	Search for Charge ordering in Untwinned LSCO

foreign+nationals:
	Yoichi Ando, CRIEPI, Tokyo

hazards:
	none

minimumdays:
	3

name:
	Eric D. Isaacs

nonmembers:
	Eric D. Isaacs, Bell Labs
	Girsh Blumberg, Bell Labs

unacceptable+dates:
	


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