Abstract:We present measurements of the plasmon shift in shock-compressed matter as a function of momentum transfer beyond the Fermi wavevector using an X-ray Free Electron Laser. We eliminate the elastically scattered signal retaining only the inelastic plasmon signal. Our plasmon dispersion agrees with both the random phase approximation (RPA) and static Local Field Corrections (sLFC) for an electron gas at both zero and finite temperature. Further, we find the inclusion of electron-ion collisions through the Born-Me… Show more
“…To that end, in Fig. 7 we show the EELF at the wave-number at which the plasmon signal was detected in a recent experiment on Aluminum 84 . We observe that, first of all, our calculations in the homogeneous system reproduce the plasmon position (black curve) measured in the experiment (purple data point).…”
Section: Experimental Feasibilitymentioning
confidence: 96%
“… Figure 7 The EELF at , , . Circle symbol indicates position of the experimentally measured plasmon location of the homogeneous WDM 84 . Vertical dashed curves correspond to uncertainty range in the experiment.…”
We investigate the emergence of electronic excitations from the inhomogeneous electronic structure at warm dense matter parameters based on first-principles calculations. The emerging modes are controlled by the imposed perturbation amplitude. They include satellite signals around the standard plasmon feature, transformation of plasmons to optical modes, and double-plasmon modes. These modes exhibit a pronounced dependence on the temperature. This makes them potentially invaluable for the diagnostics of plasma parameters in the warm dense matter regime. We demonstrate that these modes can be probed with present experimental techniques.
“…To that end, in Fig. 7 we show the EELF at the wave-number at which the plasmon signal was detected in a recent experiment on Aluminum 84 . We observe that, first of all, our calculations in the homogeneous system reproduce the plasmon position (black curve) measured in the experiment (purple data point).…”
Section: Experimental Feasibilitymentioning
confidence: 96%
“… Figure 7 The EELF at , , . Circle symbol indicates position of the experimentally measured plasmon location of the homogeneous WDM 84 . Vertical dashed curves correspond to uncertainty range in the experiment.…”
We investigate the emergence of electronic excitations from the inhomogeneous electronic structure at warm dense matter parameters based on first-principles calculations. The emerging modes are controlled by the imposed perturbation amplitude. They include satellite signals around the standard plasmon feature, transformation of plasmons to optical modes, and double-plasmon modes. These modes exhibit a pronounced dependence on the temperature. This makes them potentially invaluable for the diagnostics of plasma parameters in the warm dense matter regime. We demonstrate that these modes can be probed with present experimental techniques.
“…If, on the other hand, the plasmon resonance is measured at different scattering angles for a fixed compression condition, the plasmon dispersion is determined. Its shape, in particular at larger momentum transfer exceeding the Fermi wavevector, allows to distinguish the influence of collisional processes and local field corrections at high pressures [104].…”
Section: Inelastic X-ray Scattering and The Dielectric Functionmentioning
Synchrotrons and free electron lasers are unique facilities to probe the atomic structure and electronic properties of matter at extreme thermodynamical conditions. In this context, ‘matter at extreme pressures and temperatures’ was one of the science drivers for the construction of low emittance 4th generation synchrotron sources such as the Extremely Brilliant Source of the European Synchrotron Radiation Facility and hard x-ray free electron lasers, such as the European x-ray free electron laser. These new user facilities combine static high pressure and dynamic shock compression experiments to outstanding high brilliance and submicron beams. This combination not only increases the data-quality but also enlarges tremendously the accessible pressure, temperature and density space. At the same time, the large spectrum of available complementary x-ray diagnostics for static and shock compression studies opens unprecedented insights into the state of matter at extremes. The article aims at highlighting a new horizon of scientific opportunities based on the synergy between extremely brilliant synchrotrons and hard x-ray free electron lasers.
“…Combining such a setup with x-ray and optical diagnostics, the electronic response of WDM [107] is accessed. Higher densities and, therefore, higher pressures can also be reached via isentropic or shock compression using high intensity laser pulses [34,108]. The technical details of our TDDFT calculations are listed in Appendix A.…”
Section: B Extreme Conditionsmentioning
confidence: 99%
“…In the compressed case, the available data set is restricted to two measurements, i.e., at small and large q [108].…”
The numerical modeling of plasmon behavior is crucial for an accurate interpretation of inelastic scattering diagnostics in many experiments. We highlight the utility of linear-response timedependent density functional theory (LR-TDDFT) as an appropriate first-principles framework for a consistent modeling of plasmon properties. We provide a comprehensive analysis of plasmons from ambient throughout warm dense conditions and assess typical properties such as the dynamical structure factor, the plasmon dispersion, and the plasmon width. We compare them with experimental measurements in aluminum accessible via x-ray Thomson scattering and with other dielectric models such as the Lindhard model, the Mermin approach based on parametrized collision frequencies, and the dielectric function obtained using static local field corrections of the uniform electron gas parametrized from path integral Monte Carlo simulations both at the ground state and at finite temperature. We conclude with the remark that the common practice of extracting and employing plasmon dispersion relations and widths is an insufficient procedure to capture the complicated physics contained in the dynamic structure factor in its full breadth.
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