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Context. Stellar feedback plays a crucial role in star formation and the life cycle of molecular clouds. The intense star formation region 30 Doradus, which is located in the Large Magellanic Cloud (LMC), is a unique target for detailed investigation of stellar feedback owing to the proximity of the hosting galaxy and modern observational capabilities that together allow us to resolve individual molecular clouds – nurseries of star formation. Aims. We study the impact of large-scale feedback on the molecular gas using the new observational data in the 12CO(3 − 2) line obtained with the APEX telescope. Methods. Our data cover an unprecedented area of 13.8 sq. deg. of the LMC disc with a spatial resolution of 5 pc and provide an unbiased view of the molecular clouds in the galaxy. Using these data, we located molecular clouds in the disc of the galaxy, estimated their properties, such as the areal number density, relative velocity and separation, width of the line profile, CO line luminosity, size, and virial mass, and compared these properties of the clouds of 30 Doradus with those in the rest of the LMC disc. Results. We find that, compared with the rest of the observed molecular clouds in the LMC disc, those in 30 Doradus show the highest areal number density; they are spatially more clustered, they move faster with respect to each other, and they feature larger linewidths. In parallel, we do not find statistically significant differences in such properties as the CO line luminosity, size, and virial mass between the clouds of 30 Doradus and the rest of the observed field. Conclusions. We interpret our results as signatures of gas dispersal and fragmentation due to high-energy large-scale feedback. [ABSTRACT FROM AUTHOR]

Usually, the presence of multiple eigenstates (magnons and phonons) in a system makes it difficult to analyze the coupled excitation mechanism using conventional single-pulse terahertz (THz) spectroscopy. On the contrary, 2D THz spectroscopy reveals energy flows between these states, which facilitates the identification of the coupled dynamics. In this article, we provide a theoretical description of this advanced technique and an experimental demonstration of its performance in antiferromagnet CoF2. Here, 2D THz spectroscopy shows that the THz pulse induces energy transfer from the magnon mode to the Raman-active phonon mode via a nonlinear excitation pathway. [ABSTRACT FROM AUTHOR]

An intense THz pulse excites a high-Q magnetic resonance mode in the antiferromagnetic insulator HoFeO3 by the THz Zeeman torque. By using magneto-optical detection and sweeping the temperature, we observed an anomalous beating in the magnon dynamics for certain temperatures. The beating originates from the formation of cavity magnon-polaritons upon the intersection of the antiferromagnetic resonance frequency with the frequencies of the Fabry–Pérot modes inside the etalon formed by the sample cavity in the weak coupling limit. The validity of this idea is demonstrated by simulations using Maxwell's equations. Furthermore, the observed beating pattern depends on the polarization of the probe pulse. This dependence can be reproduced in the simulations by considering an imaginary Verdet constant, which could be a result of an interplay between the magneto-optical Faraday effect and static linear birefringence. [ABSTRACT FROM AUTHOR]

Employing polarization sensitive terahertz (THz) transmission spectroscopy, we explored how the waveform of initially single-cycle linearly polarized THz pulses changes upon propagation through a thick antiferromagnetic crystal of CoF2. The changes upon propagation through CoF2 are found to depend strongly on both the incoming polarization and temperature. In particular, the ellipticity and polarization rotation acquired by initially linearly polarized light are quantified and explained in terms of magnetic linear birefringence and dichroism. Although the magneto-optical effects are often considered to be relatively weak, our experiments reveal that the polarization of the THz pulse substantially changes along the pulse duration. The pulse shape is further complicated by features assigned to the formation of magnon-polaritons. The findings clearly show the importance of accounting for propagation effects in antiferromagnetic spintronics and magnonics. [ABSTRACT FROM AUTHOR]

Subpicosecond pumping of ferromagnetic semiconductor InMnAs in the ranges of intra- and interband electronic transitions can result in an efficient demagnetization of the medium up to 60% of the initial magnetic moment. Here, we report about the efficiency of ultrafast demagnetization by a duo of terahertz and infrared pulses that trigger intra- and interband electronic transitions, respectively. Varying the intensities of the pulses and the delay between them, we study the degree of demagnetization caused by the pulse duo. It is shown that the result of the excitation does not depend on the pulse sequence. Our findings indicate that both intra- and interband electronic transitions result in ultrafast demagnetization of the semiconductor via the very same mechanism, which evolves at a ps timescale. Independent of the origin of the electronic transition, ultrafast demagnetization is a result of a temperature increase in the free charge carriers (holes). [ABSTRACT FROM AUTHOR]

The light scattering in the form of ring structures in SnPS crystals at the propagation of intense laser pump radiation along the b crystallographic axis is detected. Radiation passing through a crystal is completely scattered into a cone whose angle increases with the pump power and decreases reversibly with a decrease in this power. The observed effect can be attributed to a spontaneous increase in the amplitude of photoinduced bulk diffraction gratings and to the scattering of light on them in the directions where the phase increments of the photorefractive and diffraction natures compensate each other. A similar type of scattering was observed previously in other photorefractive crystals, but the appearance of gratings with the period easily varied by varying the pump power is demonstrated for the first time. [ABSTRACT FROM AUTHOR]

Optical second harmonic generation at the photon energy of 2ℏω = 2eV in the model centrosymmetric antiferromagnet NiO irradiated with picosecond terahertz pulses (0.4-2.5 THz) at room temperature is detected. The analysis of experimental results shows that induced optical second harmonic generation at the moment of the impact of a terahertz pulse arises through the electric dipole mechanism of the interaction of the electric field of a pump pulse with the electron subsystem of NiO. Temporal changes in optical second harmonic generation during 7 ps after the action of the pulse are also of an electric dipole origin and are determined by the effects of propagation of the terahertz pulse in a NiO platelet. Coherent oscillations of spins at the antiferromagnetic resonance frequency induced by the magnetic component of the terahertz pulse induce a relatively weak modulation of magnetic dipole optical second harmonic generation. [ABSTRACT FROM AUTHOR]

WSe films have been studied by the method of second harmonic generation (SHG) in the 1200-1420 nm wavelength range at room temperature. Preliminary investigations of photoluminescence spectra and atomic force microscopy showed that the film consists of extended microcrystals and has a thickness of about 1 nm, which corresponds to a single monolayer. The SHG intensity spectrum showed the presence of a 1s (B)-exciton for 1.95-eV photon energy. [ABSTRACT FROM AUTHOR]

The ultrafast dynamics of electrons and phonons excited by femtosecond light pulses in ferroelectric semiconductor SnPS is investigated using the optical pump-probe technique. It is demonstrated that a soft mode can be excited in this ferroelectric in the vicinity of the phase transition initiated by laser radiation. [ABSTRACT FROM AUTHOR]