Erratum: Dynamics and scaling in a quantum spin chain material with bond randomness. [Phys. Rev. Lett 93, 077206 (2004)]
T. Masuda
erratum1.1.tex
\newcommand{\BaCuSiO}{BaCu$_2$Si$_2$O$_7$}

\newcommand{\BaCuSiGexO}{BaCu$_2$(Si$_{1-x}$Ge$_x$)$_2$O$_7$}

\newcommand{\BaCuSiGeO}{BaCu$_2$(Si$_{0.5}$Ge$_{0.5}$)$_2$O$_7$}

\newcommand{\BaCuGeO}{BaCu$_2$Ge$_2$O$_7$}


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\begin{document}
\title{Erratum: Dynamics and scaling in a quantum spin chain material with bond randomness.
[Phys. Rev. Lett 93, 077206 (2004)] }

\author{T. Masuda}
\author{A. Zheludev}
\author{K. Uchinokura}
\author{J.-H. Chung}
\author{S. Park}

\maketitle



The described experiments were performed on a rather small
\BaCuSiGeO\ single crystal sample of approximate mass 0.5 g. We
have since performed follow-up neutron studies using a much larger
($\approx$7~g) sample, to verify our initial result and to extend
the measurements to higher energy transfers \cite{Zheludev2006}.
To our dismay, the new results were in contradiction with the
original findings. As shown in Fig.~\ref{fig}, $\omega S(\omega)$
measured on the new sample (circles) increases linearly in the
range 2.5--45~meV. Moreover, we found no anomalous wave-vector
broadening of the inelastic peaks. The widths and peak shapes at
all energies are fully accounted for by the M\"uller ansatz
\cite{Muller}, that approximates the dynamic structure factor in
disorder-free quantum spin chains, assuming $J=37$~meV for
\BaCuSiGeO.

\begin{figure}
\includegraphics[width=3in]{fig.eps}
\caption{Scaling of $\omega S(\omega)$ measured in
\protect\BaCuSiGeO\ at $T=4$ and $T=12$~K using the new sample
(circles, \protect\cite{Zheludev2006}), and the corrected original
data (triangles). Open, greyed and black symbols correspond to
time-of-flight (MAPS spectrometer at ISIS), thermal-neutron 3-axis
(HB1 instrument at ORNL) and cold-neutron 3-axis (SPINS
spectrometer at NIST) measurements, respectively.\label{fig}}
\end{figure}

Reviewing the raw data of the initial study, we found two separate
sources of systematic error that affected the data analysis. The
first problem had to do with background subtraction. Assuming a
linear background appears to have been a bad choice for the scans
collected at 12 and 15~meV energy transfers. By comparing scans
measured in the new sample at several equivalent wave vectors we
concluded that the original scans are distorted by an underlying
broad background peak. As a result, the signal appeared more
intense and broader than in reality, and had the unusual
Lorentzian shape. The second problem was caused by an trivial
mistake in the data reduction: we have incorrectly applied the
$\lambda/2$ correction for efficiency of the thermal neutron flux
monitor. Once the data points affected by the structured
background are dropped, and the $\lambda/2$ correction is properly
applied, the intensity scaling deduced from the original
experiment (Fig.~1, triangles) becomes consistent with the new
measurements of \cite{Zheludev2006} (circles).

We sincerely apologies for the misguided analysis and
interpretation of the neutron data. However, we would like to
re-iterate that quenched disorder in \BaCuSiGeO\ is present and
manifests itself in the unusual behavior of magnetic
susceptibility and other bulk properties.



\begin{thebibliography}{99}


\bibitem{Zheludev2006} A. Zheludev, T. Masuda, G. Dhalenne, A.
Revcolevschi, C. Frost and T. Perring, to be published (2006).


\bibitem{Muller} G. M\"{u}ller, H. Thomas, M.~W. Puga, and H. Beck, J. Phys. C {\bf
14}, 3399 (1981).

\end{thebibliography}


\pagebreak

\end{document}

cond-mat0404688.extracted_bib
\begin{thebibliography}{99}


\bibitem{Zheludev2006} A. Zheludev, T. Masuda, G. Dhalenne, A.
Revcolevschi, C. Frost and T. Perring, to be published (2006).


\bibitem{Muller} G. M\"{u}ller, H. Thomas, M.~W. Puga, and H. Beck, J. Phys. C {\bf
14}, 3399 (1981).

\end{thebibliography}