Project

Ultrafast dynamics of phase transitions; Femtosecond x-ray diffraction; Ultrafast phenomena in solid matter; manganites; ultrafast phenomena

Lead
Lay summary
In the past two decades modern solid state research has discovered many new materials with exotic but highly technologically relevant properties such as high-temperature superconductivity, colossal magnetoresistance, and multiferroicity. A common feature of these materials, often referred to as "strongly correlated electron systems," is a complex phase diagram arising from strong interactions among local charges, orbitals, spins, and distortions of the atomic lattice. Since standard perturbation theory usually fails to describe these effects even qualitatively, understanding these correlations poses a great challenge for modern physics. One approach to understanding the complex interactions between different degrees of freedom in strongly correlated systems is to use time-resolved methods to study the response of a material after it has been driven out of equilibrium on a time scale shorter or comparable to the period of the fastest atomic vibrations of 10 - 1000 femtoseconds (1 fs = 0.000000000000001 s). Our proposed studies will focus on several related perovskite manganite compounds. We will study the proposed manganites over a wide parameter range with ultrafast optical methods and will study selected samples with femtosecond x-ray diffraction. Time-resolved X-ray measurements can offer new physical insights into these strong correlations by separating correlated effects in the time domain, giving direct access to the dynamic atomic and electronic long range structure. In addition our research offers the opportunity to develop experimental techniques that have important future ap-plication to other areas of fundamental research. In view of the emerging XFEL facilities (XFEL = x-ray free electron laser), which soon will deliver x-ray beams of high brilliance and ultrashort duration, it is vitally important to the scientific community to refine and develop experimental methods to tackle new emerging scientific problems on ultrashort time scales.

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Last update: 21.02.2013

Active participation

Self-organised

Number	Title	Start	Funding scheme

The proposed research will advance our current understanding of the interplay of the electronic system with the lattice in strongly correlated electron systems. In many such solids there are strong coupling mechanisms between the electronic and lattice energy subsystems, often resulting in a subtle balance between opposing forces. Femtosecond x-ray diffraction is a unique tool that provides unambiguous, quantitative structural information on time scales relevant for the lattice dynamics of these systems. Our proposed studies will focus on several related manganite compounds. We intend to measure in the same systems both the structural dynamics using femtosecond x-ray diffraction and the static electronic ordering using resonant diffraction. The ultimate goal of our studies at the SLS is to combine these efforts towards a time-resolved resonant x-ray diffraction experiment at the FLASH soft x-ray FEL and at future hard x-ray FELs to reveal correlated structural and electronic dynamics as they develop. In the present proposal we ask for funding of a PhD student. He or she will study the proposed manganites over a wide parameter range with ultrafast optical methods and will study selected samples together with the FEMTO team with femtosecond x-ray diffraction. The FEMTO-project at the Swiss Light Source (SLS) is currently the only operational tunable source delivering femtosecond hard x-rays tunable in the energy range from 5 to 12 keV with a well-collimated beam. The proposed diffraction experiments in the hard x-ray range cannot be performed today at any other facility worldwide.