Femtosecond Buildup of a Many-Body Resonance Observed via Two-Dimensional THz Time-Domain Spectroscopy

Huber, Rupert; Tauser, F.; Brodschelm, A.; Leitenstorfer, Alfred

doi:10.1002/1521-3951(200211)234:1<207::aid-pssb207>3.0.co;2-z

Cited by 6 publications

(14 citation statements)

References 18 publications

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“…Interestingly, both solutions, the one for the Hubbard lattice (7) and the one for the gas of particle (21) lead to the same result of the integral equation (16) for the two-time response function The pump pulse was at t0 = −40fs and the probe pulse has a full-width at half-maximum of 27f s. Circles are data from [1,4], solid lines show the electronic part (22) published in [20]. The plasma frequency is given by ωp =14.4 THz and the relaxation time is τ = 85 fs.…”

Section: With the Timedependent Density N(t)mentioning

confidence: 99%

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Universal short-time response and formation of correlations after quantum quenches

Morawetz

2014

Phys. Rev. B

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The short-time evolution of two distinct systems, the pump and probe experiments with semiconductor and the sudden quench of cold atoms in an optical lattice, is found to be described by the same universal response function. This analytic formula at short time scales is derived from the quantum kinetic theory approach observing that correlations need time to be formed. The demand of density conservation leads to a reduction of the relaxation time by a factor of four in quench setups. The influence of finite trapping potential is derived and discussed as well as Singwi-Sjølander local field corrections.

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Section: With the Timedependent Density N(t)mentioning

confidence: 99%

“…Besides pump-and probe experiments in semiconductors like GaAs [1] or InP [2] where the formation of collective modes and quasiparticles have been observed with the help of femtosecond spectroscopy, it is now possible to measure the time-dependent occupation of Hubbard-like set ups and to observe the formation of correlations [3].…”

Section: Introductionmentioning

confidence: 99%

Universal short-time response and formation of correlations after quantum quenches

Morawetz

2014

Phys. Rev. B

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“…The femtosecond spectroscopy has opened the exciting possibility to observe directly the formation of collective modes and quasiparticles in interacting many-body systems. This formation is reflected in the time dependence of the dielectric function [1,2,3] or terahertz emission [4]. For an overview over theoretical and experimental work see [5,6].…”

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confidence: 99%

“…The experimental data in semiconductors like GaAs [2] or InP [3] reveal similar features. These features are explained by several numerically demanding calculations.…”

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Femtosecond formation of collective modes due to mean-field fluctuations

2005

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Starting from a quantum kinetic equation including the mean field and a conserving relaxationtime approximation we derive an analytic formula which describes the time dependence of the dielectric function in a plasma created by a short intense laser pulse. This formula reproduces universal features of the formation of collective modes seen in recent experimental data of femtosecond spectroscopy. The presented formula offers a tremendous simplification for the description of the formation of quasiparticle features in interacting systems. Numerical demanding treatments can now be focused on effects beyond these gross features found here to be describable analytically.PACS numbers: 71.45. Gm, 78.47.+p, 42.65.Re, 82.53.Mj The last ten years have been characterized by an enormous activity about ultrafast excitations in semiconductors, clusters, or plasmas by ultrashort laser pulses. The femtosecond spectroscopy has opened the exciting possibility to observe directly the formation of collective modes and quasiparticles in interacting many-body systems. This formation is reflected in the time dependence of the dielectric function [1, 2, 3] or terahertz emission [4]. For an overview over theoretical and experimental work see [5,6]. Such ultrafast excitations in semiconductors have been satisfactorily described by calculating nonequilibrium Green's functions [7,8]. This approach allows one to describe the formation of collective modes [3,9] and even exciton population inversions [10].The experimental data in semiconductors like GaAs [2] or InP [3] reveal similar features. These features are explained by several numerically demanding calculations. Since some common features are robust, i.e., independent of the actual used material parameters, it should be possible to describe them by a simple theory. The origin of such robust features likely rests in the short-or transienttime behavior itself. At short times higher-order correlations have no time yet to develop, therefore the dynamics is controlled exclusively by mean-field forces.Based on the mean-field character of the short-time evolution we intend to derive a time-dependent response function from the mean-field linear response. We will start from a conserving relaxation-time approximation which dates back to an idea of Mermin [11,12]. Our aim is a simple analytic formula suitable for fits of experimental data.The electron motion is controlled by the kinetic energŷ E, the external perturbationV ext and the induced meanfield potentialV ind . The corresponding kinetic equation for the one-particle reduced density matrixρ readṡwith the relaxation time τ and a local equilibrium density matrixρ l.e. determined in the following. We will calculate the response in the momentum representationwhere |p is an eigenstate of momentum p. For interpretations it is more convenient to transform the reduced density matrix to the Wigner distribution in phase spacewhere R is the spatial coordinate. The relaxation process in Eq.(1) tends to establish a local equilibrium. Following Mermin...

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Dynamic Processes

Klingshirn¹

2010

Zinc Oxide

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Femtosecond Buildup of a Many-Body Resonance Observed via Two-Dimensional THz Time-Domain Spectroscopy

Cited by 6 publications

References 18 publications

Universal short-time response and formation of correlations after quantum quenches

Universal short-time response and formation of correlations after quantum quenches

Femtosecond formation of collective modes due to mean-field fluctuations

Dynamic Processes

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