Temperature-dependent x-ray diffraction of the low-dimensional spin 1/2
quantum magnet TiOCl shows that the phase transition at T_{c2} = 90 K
corresponds to a lowering of the lattice symmetry. Below T_{c1} = 66 K a
twofold superstructure develops, that indicates the formation of spin-singlet
pairs via direct exchange between neighboring Ti atoms, while the role of
superexchange is found to be negligible. TiOCl thus is identified as a
spin-Peierls system of pure 1D chains of atoms. The first-order character of
the transition at T_{c1} is explained by the competition between the
structurally deformed state below T_{c2} and the spin-Peierls state below
T_{c1}.Comment: Phys. Rev. B (Rapid Communications) in pres
Fluorescence detection is a convenient way to measure x-ray absorption spectra in situations where samples cannot be made in the required configuration. However, self-absorption effects cause considerable distortion of spectra measured in fluorescence. We describe a straightforward procedure to correct for such distortion in the hard-x-ray region using the known energy dependence of the x-ray absorption coefficients. This procedure is used to obtain the vanadium K-edge spectrum of single crystal V 2 O 3 and we demonstrate that self-absorption is properly corrected. This facilitates the use of fluorescence detection even in the hard-x-ray region.
We have studied the electronic structure of the spin-1/2 quantum magnet TiOCl by polarizationdependent momentum-resolved photoelectron spectroscopy. From that, we confirm the quasi-onedimensional nature of the electronic structure along the crystallographic b-axis and find no evidence for sizable phonon-induced orbital fluctuations as origin for the non-canonical phenomenology of the spin-Peierls transition in this compound. A comparison of the experimental data to our own LDA+U and Hubbard model calculations reveals a striking lack of understanding regarding the quasi-one-dimensional electron dispersions in the normal state of this compound.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.