Reply: In the preceding Comment [1], Narozhny and Fedotov (NF) raise several points of criticism regarding the validity of our recent Letter [2] on the muon decay in a laser field. NF argue that the parameters eE 0 =m ! and E S m 2 c 3 =e@ are very small in our case, and hence there are no reasons for a noticeable change of the muon lifetime (here m 207m e , e is the electric charge, E 0 and ! are the electric field amplitude of the laser and its frequency). We agree on the smallness of these two parameters; physically, quantifies the velocity of the muon quiver motion in the laser field whereas the condition for the value of E S follows from the requirement that the energy transferred from the laser field to the muon within a Compton wave length of the muon should be comparable to the rest energy of the muon, i.e., e E S m c 2 [here h=m c]. In our case, the field is weak, and since the moun is heavy, the laser dressing of the moun plays only a minor role and is, therefore, as stated in our Letter, neglected altogether in [2]. As discussed in details in [2], we argued that the driving mechanism for the laserassisted decay is the laser dressing of the electronic states. So while we agree to the NF estimates of and E S and to the expectations based upon them, these parameters do not determine the nonlinear energy and momentum transfer from the laser field within our adopted framework. Furthermore, NF indicate that Ref.[3] should have been cited. We agree on this point, even though we referred to the related works (Refs. [14, 15] of [2]) where [3] is discussed. NF further discuss our Eq. (6) and draw attention to a missing 2 prefactor and that E in the integrand should read E . These two corrections are typographical errors. This can also be inferred from Fig. (2) of [2] where our low-field results coincide with the laser-free case, as NF expect. In an attempt to derive explicit expressions for the decay rate, NF drop in our equation (6) the terms 1 l altogether, and they obtain their expression (1) from which they conclude that there should be no laser-induced enhancement. We note that, as stated in [2], the functions 1 l and their interplay are decisive to accomplish our results [the cutoff on the allowed l and hence on the 1 l contributions is evident from Fig. (1)]. It is still to be clarified to which extent the formula Eq. (1) proposed by NF conforms to our full numerical calculations. As for the general validity of our model, we remark that, as explicitly stated in [2], we drop in the Volkov state the dependence on terms quadratic in the vector potential due to the relatively weak laser fields under consideration. We also ignored completely the direct laser influence on the moun, for the reasons mentioned above. At this stage, it is not clear whether and to which extent the incorporation of these additional factors in the calculations would alter the conclusions of [2].

Using a combination of first-principles and magnetization-dynamics calculations, we study the effect of the intense optical excitation of phonons on the magnetic behavior in insulating magnetic materials. Taking the prototypical magnetoelectric Cr2O3 as our model system, we show that excitation of a polar mode at 17 THz causes a pronounced modification of the magnetic exchange interactions through a change in the average Cr-Cr distance. In particular, the quasi-static deformation induced by nonlinear phononic coupling yields a structure with a modified magnetic state, which persists for the duration of the phonon excitation. In addition, our time-dependent magnetization dynamics computations show that systematic modulation of the magnetic exchange interaction by the phonon excitation modifies the magnetization dynamics. This temporal modulation of the magnetic exchange interaction strengths using phonons provides a new route to creating non-equilibrium magnetic states and suggests new avenues for fast manipulation of spin arrangements and dynamics. arXiv:1707.03216v3 [cond-mat.str-el]

Recent experiments access the time-resolved photoelectron signal originating from plasmon satellites in correlated materials and address their build-up and decay in real time. Motivated by these developments, we present the Kadanoff-Baym formalism for the nonequilibrium time evolution of interacting fermions and bosons. In contrast to the fermionic case the bosons are described by second-order differential equations. Solution of the bosonic Kadanoff-Baym equations -which is the central ingredient of this work -requires substantial modification of the usual two-times electronic propagation scheme. The solution is quite general and can be applied to a number of problems, such as the interaction of electrons with quantized photons, phonons and other bosonic excitations. Here, the formalism is applied to the photoemission from a deep core hole accompanied by plasmon excitation. We compute the time-resolved photoelectron spectra and discuss the effects of intrinsic and extrinsic electron energy losses and their interference.

A quantum thermodynamic cycle with a chiral multiferroic working substance such as LiCu2O2 is presented. Shortcuts to adiabaticity are employed to achieve an efficient, finite time quantum thermodynamic cycle which is found to depend on the spin ordering. The emergent electric polarization associated with the chiral spin order, i.e. the magnetoelectric coupling, renders possible steering of the spin order by an external electric field and hence renders possible an electric-field control of the cycle. Due to the intrinsic coupling between of the spin and the electric polarization, the cycle performs an electro-magnetic work. We determine this work's mean square fluctuations, the irreversible work, and the output power of the cycle. We observe that the work mean square fluctuations are increased with the duration of the adiabatic strokes while the irreversible work and the output power of the cycle show a non-monotonic behavior. In particular the irreversible work vanishes at the end of the quantum adiabatic strokes. This fact confirms that the cycle is reversible. Our theoretical findings evidence the existence of a system inherent maximal output power. By implementing a Lindblad master equation we quantify the role of thermal relaxations on the cycle efficiency. We also discuss the role of entanglement encoded in the non-collinear spin order as a resource to affect the quantum thermodynamic cycle.

Vanadium dioxide, an archetypal correlated-electron material, undergoes an insulator-metal transition near room temperature that exhibits electron-correlation-driven and structurally-driven physics. Using ultrafast optical spectroscopy and x-ray scattering we show that these processes can be disentangled in the time domain. Specifically, following intense sub-picosecond electric-field excitation, a partial collapse of the insulating gap occurs within the first ps. Subsequently, this electronic reconfiguration initiates a change in lattice symmetry taking place on a slower timescale. We identify the kinetic energy increase of electrons tunneling in the strong electric field as the driving force, illustrating a novel method to control electronic interactions in correlated materials on an ultrafast timescale.