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      Femtosecond dynamics of magnetic excitations from resonant inelastic x-ray scattering in CaCu2O3

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          Abstract

          Taking spinon excitations in the quantum antiferromagnet CaCu2O3 as an example, we demonstrate that femtosecond dynamics of magnetic excitations can be probed by direct resonant inelastic x-ray scattering (RIXS). To this end, we isolate the contributions of single and double spin-flip excitations in experimental RIXS spectra, identify the physical mechanisms that cause them and determine their respective timescales. By comparing theory and experiment, we find that double spin flips need a finite amount of time to be generated, rendering them sensitive to the core-hole lifetime, whereas single spin flips are to a very good approximation independent of it. This shows that RIXS can grant access to time-domain dynamics of excitations and illustrates how RIXS experiments can distinguish between excitations in correlated electron systems based on their different time dependence.

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          Most cited references5

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          Attosecond spectroscopy in condensed matter.

          Comprehensive knowledge of the dynamic behaviour of electrons in condensed-matter systems is pertinent to the development of many modern technologies, such as semiconductor and molecular electronics, optoelectronics, information processing and photovoltaics. Yet it remains challenging to probe electronic processes, many of which take place in the attosecond (1 as = 10(-18) s) regime. In contrast, atomic motion occurs on the femtosecond (1 fs = 10(-15) s) timescale and has been mapped in solids in real time using femtosecond X-ray sources. Here we extend the attosecond techniques previously used to study isolated atoms in the gas phase to observe electron motion in condensed-matter systems and on surfaces in real time. We demonstrate our ability to obtain direct time-domain access to charge dynamics with attosecond resolution by probing photoelectron emission from single-crystal tungsten. Our data reveal a delay of approximately 100 attoseconds between the emission of photoelectrons that originate from localized core states of the metal, and those that are freed from delocalized conduction-band states. These results illustrate that attosecond metrology constitutes a powerful tool for exploring not only gas-phase systems, but also fundamental electronic processes occurring on the attosecond timescale in condensed-matter systems and on surfaces.
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            SAXES, a high resolution spectrometer for resonant x-ray emission in the 400–1600 eV energy range

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              Spinons in the strongly correlated copper oxide chains in SrCuO2

              We have investigated the spin dynamics in the strongly correlated chain copper oxide SrCuO\(_2\) for energies up to \(\gtrsim 0.6\) eV using inelastic neutron scattering. We observe an acoustic band of magnetic excitations which is well described by the "Muller-ansatz" for the two-spinon continuum in the S=1/2 antiferromagnetic Heisenberg spin chain. The lower boundary of the continuum extends up to \(\approx 360\) meV, which corresponds to an exchange constant \(J = 226(12)\) meV. Our finding that an effective Heisenberg spin Hamlitonian adequately describes the spin sector of this 1D electron system, even though its energy scale is comparable to that of charge excitations, provides compelling experimental evidence for spin-charge separation.
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                Author and article information

                Journal
                31 July 2013
                Article
                10.1103/PhysRevLett.112.147401
                1307.8393
                69043c81-78ea-401a-8107-c5b36fd13afe

                http://arxiv.org/licenses/nonexclusive-distrib/1.0/

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                Custom metadata
                Physical Review Letters 112, 147401 (2014)
                cond-mat.str-el

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