Berlin 2012 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 43: Correlated Electrons: Metal-Insulator Transition 2
TT 43.4: Vortrag
Donnerstag, 29. März 2012, 15:45–16:00, H 3010
Hour-glass dispersion in overdoped single-layered manganites — •H. Ulbrich1, P. Steffens2, D. Lamago3, Y. Sidis3, and M. Braden1 — 1University of Cologne — 2ILL, Grenoble, France — 3LLB Saclay, France
The mechanism of the high-Tc superconductivity in the cuprates is still an unsolved problem in modern solid state physics. Stripe ordering may
play an important role in the physics of high-Tc superconductors. Experimentally, observations of the spin-wave dispersion which forms a shape
like an hour-glass have been taken as proof for stripe scenarios in the cuprates [1]. Stripe ordering can be observed in several
transition-metal compounds. In manganites, additionally the eg-orbitals on Mn3+ ions play a crucial role. A pattern for the ordering
schema in overdoped manganites (x>1/2) has just been established [2]. We studied the single-layered systems Re1−xA1+xMnO4 (Re=Pr,Nd; A=Ca,Sr) with x=2/3. The position of the magnetic superstructure reflections of Mn4+
exhibits a fourfold pattern. Inelastic neutron data around the incommensurate magnetic satellites reveal an hour-glass like spin-wave
dispersion, comparable to the cuprates and recently in cobaltates [1,3]. However, our dispersion in the Pr0.33Ca1.67MnO4 compound,
which exhibits a large correlation length of the magnetic order, showing a branch dispersing outward from the incommensurate zone-center. Upon
heating, the correlation length decreases and concomitantly, the dispersion develops in a full hour-glass shape.
J.M. Tranquada et al., Nature, 429, 534 (2004).
H. Ulbrich et al., Phys. Rev. Lett. 106, 157201 (2011).
A.T. Boothroyd et al., Nature 471, 341 (2011).