New Scientific Opportunities at the European Synchrotron Radiation ...

European Synchrotron Radiation Facility Long-Term Strategy 7 July 2006
basic research effort towards the development of a future quantum computer.
Studies in magnetic fields of unprecedented strength will lead to the discovery of
novel effects and will have a decisive influence on the better understanding of
semiconductors, superconductors and magnetic materials. The use of hard X-rays
as a probe of materials subjected to intense magnetic fields will offer unique
possibilities, as is the case for infrared spectroscopy, where the (soft radiation) free
electron laser ELBE at the high magnetic field laboratory in Dresden will allow
experiments up to 100T.
Although an increasing number of different experimental methods have been
employed over the last decade, X-ray diffraction is expected to remain the most
widely used technique in the context of extreme conditions research because it
provides fundamental structural information that is the basis for other synchrotron
techniques. This area requires a major effort in the development of new beamlines,
new instrumentation (particularly in sample environment and X-ray detectors), and in
the related scientific infrastructure.
New Science: illustrative examples
The construction and installation of a multi-analyser spectrometer capable of
retrieving the sample's complete phonon dispersion curve at only one setting
of the spectrometer (and sample) would enable, for example, the study of
single crystal minerals under pressure and temperature conditions of the
Earth's mantle which can only be reached by combining diamond anvil cell
techniques and laser heating. This is currently impossible due to low countrates
and the difficulties of orienting the sample crystal (in its complicated
sample environment) at many different angles.
Quantum effects in magnetic systems are enhanced by low dimensionality,
low spin and frustrated interactions. Two-dimensional “spin dimer” systems,
where the magnetic interactions are strongly anisotropic and the spin dimers
form spin singlet ground states, are especially interesting. By applying an
external magnetic field above 20 Tesla, we may close the spin gap and form
a gas of spin triplets. At certain characteristic field strengths plateaus are
observed in the magnetisation curves. These arise from the crystallisation of
the triplets into superlattices. Their precise nature is still controversial as no
direct microscopic probes are currently available. Through studies of the
corresponding superlattice reflections under extremely high applied magnetic
fields (above 20T), X-ray resonant magnetic scattering will provide direct
insight into the long range interactions of the triplets. In addition, X-ray
spectroscopy, in particular resonant inelastic x-ray scattering, will
complement these data with information on the relevant energy scales and
local symmetries.
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