Anomalous expansion of the copper-apical-oxygen distance in superconducting cuprate bilayers.
We have introduced an improved x-ray phase-retrieval method with unprecedented speed of convergence and precision, and used it to determine with sub-Angstrom resolution the complete atomic structure of epitaxial La(2-x)Sr(x)CuO(4) ultrathin films. We focus on superconducting heterostructures built from constituent materials that are not superconducting in bulk samples. Single-phase metallic or superconducting films are also studied for comparison. The results show that this phase-retrieval diffraction method enables accurate measurement of structural modifications in near-surface layers, which may be critically important for elucidation of surface-sensitive experiments. Specifically we find that, while the copper-apical-oxygen distance remains approximately constant in single-phase films, it shows a dramatic increase from the metallic-insulating interface of the bilayer towards the surface by as much as 0.45 A. The apical-oxygen displacement is known to have a profound effect on the superconducting transition temperature.
Zhou
Hua
H
Brookhaven National Laboratory, Upton, NY 11973, USA.
Yacoby
Yizhak
Y
Butko
Vladimir Y
VY
Logvenov
Gennady
G
Bozovic
Ivan
I
Pindak
Ron
R
Phys Rev Lett. 2001 Jul 23;87(4):047003
11461638
Nat Mater. 2002 Oct;1(2):99-101
12618822
Proc Natl Acad Sci U S A. 2008 Mar 4;105(9):3203-8
18287001
Science. 2007 Aug 31;317(5842):1196-9
17673621
Phys Rev Lett. 2009 Mar 13;102(10):107004
19392148
Phys Rev Lett. 2008 Oct 10;101(15):156401
18999620
Phys Rev Lett. 2008 Aug 1;101(5):057005
18764422
Acta Crystallogr A. 2005 Jul;61(Pt 4):418-25
15972995
Phys Rev B Condens Matter. 1991 Feb 1;43(4):2968-2982
9997599
Phys Rev B Condens Matter. 1991 Oct 1;44(14):7601-7606
9998675
Acta Crystallogr A. 2003 May;59(Pt 3):201-9
12714770
Nat Mater. 2008 Nov;7(11):855-8
18849974
Phys Rev Lett. 2002 Sep 2;89(10):107001
12225215
Nature. 2003 Apr 24;422(6934):873-5
12712200
Phys Rev B Condens Matter. 1992 May 1;45(18):10647-10669
10000972
Nature. 2008 Oct 9;455(7214):782-5
18843365