D. Bossini - Academia.edu (original) (raw)

Papers by D. Bossini

Review of Scientific Instruments

Physical Review B

The impulsive generation of two-magnon modes in antiferromagnets by femtosecond optical pulses, s... more The impulsive generation of two-magnon modes in antiferromagnets by femtosecond optical pulses, so-called femto-nanomagnons, leads to coherent longitudinal oscillations of the antiferromagnetic order parameter that cannot be described by a thermodynamic Landau-Lifshitz approach. We argue that this dynamics is triggered as a result of a laser-induced modification of the exchange interaction. In order to describe the oscillations we have formulated a quantum mechanical description in terms of magnon pair operators and coherent states. Such an approach allowed us to derive an effective macroscopic equation of motion for the temporal evolution of the antiferromagnetic order parameter. An implication of the latter is that the photo-induced spin dynamics represents a macroscopic entanglement of pairs of magnons with femtosecond period and nanometer wavelength. By performing magneto-optical pump-probe experiments with 10 femtosecond resolution in the cubic KNiF 3 and the uniaxial K 2 NiF 4 collinear Heisenberg antiferromagnets, we observed coherent oscillations at the frequency of 22 THz and 16 THz, respectively. The detected frequencies as a function of the temperature fit the two-magnon excitation up to the Néel point. The experimental signals are described as dynamics of magnetic linear dichroism due to longitudinal oscillations of the antiferromagnetic vector.

Physica Scripta

Article 25fa pilot End User Agreement This publication is distributed under the terms of Article ... more Article 25fa pilot End User Agreement This publication is distributed under the terms of Article 25fa of the Dutch Copyright Act (Auteurswet) with explicit consent by the author. Dutch law entitles the maker of a short scientific work funded either wholly or partially by Dutch public funds to make that work publicly available for no consideration following a reasonable period of time after the work was first published, provided that clear reference is made to the source of the first publication of the work. This publication is distributed under The Association of Universities in the Netherlands (VSNU) 'Article 25fa implementation' pilot project. In this pilot research outputs of researchers employed by Dutch Universities that comply with the legal requirements of Article 25fa of the Dutch Copyright Act are distributed online and free of cost or other barriers in institutional repositories. Research outputs are distributed six months after their first online publication in the original published version and with proper attribution to the source of the original publication. You are permitted to download and use the publication for personal purposes. All rights remain with the author(s) and/or copyrights owner(s) of this work. Any use of the publication other than authorised under this licence or copyright law is prohibited. If you believe that digital publication of certain material infringes any of your rights or (privacy) interests, please let the Library know, stating your reasons.

Nature Physics, 2016

Circularly polarized optical pulses have been shown to induce a breaking of time reversal invaria... more Circularly polarized optical pulses have been shown to induce a breaking of time reversal invariance in solids, allowing for the control of magnetism through electronic Raman scattering. Here, we combine this principle with elements of magnetoelastics, and show that optical excitation of pairs of infrared-active optical phonons can excite coherent spin waves in the rare-earth orthoferrite ErFeO3. This phenomenon relies on the real-space rotations of the crystal-field atoms and on the resulting effective magnetic field onto the Fe 3+ orbitals. Coherent control of lattice rotations could be used not only in magnetic solids, but more generally in materials with interesting topological properties.

Ultrafast Bandgap Photonics, 2016

Nature Communications, 2016

The understanding of how the sub-nanoscale exchange interaction evolves in macroscale correlation... more The understanding of how the sub-nanoscale exchange interaction evolves in macroscale correlations and ordered phases of matter, such as magnetism and superconductivity, requires to bridging the quantum and classical worlds. This monumental challenge has so far only been achieved for systems close to their thermodynamical equilibrium. Here we follow in real time the ultrafast dynamics of the macroscale magnetic order parameter in the Heisenberg antiferromagnet KNiF 3 triggered by the impulsive optical generation of spin excitations with the shortest possible nanometre wavelength and femtosecond period. Our magneto-optical pump-probe experiments also demonstrate the coherent manipulation of the phase and amplitude of these femtosecond nanomagnons, whose frequencies are defined by the exchange energy. These findings open up opportunities for fundamental research on the role of short-wavelength spin excitations in magnetism and strongly correlated materials; they also suggest that nanospintronics and nanomagnonics can employ coherently controllable spin waves with frequencies in the 20 THz domain.

Springer Proceedings in Physics, 2014

Physical Review B, 2013

We demonstrate that resonant 32.3 THz pumping of f-f transitions in the samarium ions in SmFeO 3 ... more We demonstrate that resonant 32.3 THz pumping of f-f transitions in the samarium ions in SmFeO 3 leads to a nonlinear regime of radiation-matter interaction. The nonlinearity arises from the photoinduced population of the excited state, the dynamics of which was studied in a pump-probe experiment. The measurements have been performed in the spectral range near the 6 H 5 2 −→ 6 H 7 2 electronic transition. The observations show dynamics with a lifetime of 4 ps. The sign of the dynamics surprisingly differs in different spectral ranges: This phenomenon is interpreted as an excitation-induced shift of the spectral line. The results are described by the nonlinear optical polarization using the optical Bloch equations for an ensemble of two-level systems.

Unveiling the nature of the bosonic excitations that mediate the formation of Cooper pairs is a k... more Unveiling the nature of the bosonic excitations that mediate the formation of Cooper pairs is a key issue for understanding unconventional superconductivity. A fundamental step toward this goal would be to identify the relative weight of the electronic and phononic contributions to the overall frequency (Ω) dependent bosonic function, Π(Ω). We perform optical spectroscopy on Bi2Sr2Ca0.92Y0.08Cu2O 8+δ crystals with simultaneous time-and frequency-resolution; this technique allows us to disentangle the electronic and phononic contributions by their different temporal evolution. The strength of the interaction (λ∼1.1) with the electronic excitations and their spectral distribution fully account for the high critical temperature of the superconducting phase transition.

Review of Scientific Instruments, 2014

Ultrafast supercontinuum fiber-laser based pump-probe scanning magneto-optical Kerr effect micros... more Ultrafast supercontinuum fiber-laser based pump-probe scanning magneto-optical Kerr effect microscope for the investigation of electron spin dynamics in semiconductors at cryogenic temperatures with picosecond time and micrometer spatial resolution Rev. Sci. Instrum. 84, 123903 (2013); 10.1063/1.4842276

Physical Review B, 2014

ABSTRACT We present a femtosecond spectroscopic magneto-optical investigation of the coherent and... more ABSTRACT We present a femtosecond spectroscopic magneto-optical investigation of the coherent and incoherent spin dynamics in the antiferromagnetic dielectric KNiF3. The pathways of the photoinduced energy flow to spins were controlled by tuning the pump photon energy. In particular, we demonstrate that laser pulses, with photon energy tuned to a nearly-zero-absorption region, excite the spin system without any signatures of heating of electrons or phonons. In this regime the ultrafast excitation of coherent spin waves is followed by a gradual increase of the spin temperature solely due to decoherence of the laser-generated magnons, as revealed by our simultaneous measurement of both the transversal and the longitudinal component of the spin dynamics.

Physical Review Letters, 2013

A pairing gap and coherence are the two hallmarks of superconductivity. In a classical BCS superc... more A pairing gap and coherence are the two hallmarks of superconductivity. In a classical BCS superconductor they are established simultaneously at T c . In the cuprates, however, an energy gap (pseudogap) extends above T c [1, 2, 3,. The origin of this gap is one of the central issues in high temperature superconductivity. Recent experimental evidence demonstrates that the pseudogap and the superconducting gap are associated with different energy scales . It is however not clear whether they coexist independently or compete . In order to understand the physics of cuprates and improve their superconducting properties it is vital to determine whether the pseudogap is friend or foe of high temperature supercondctivity . Here we report evidence from angle resolved photoemission spectroscopy (ARPES) that the pseudogap and high temperature superconductivity represent two competing orders. We find that there is a direct correlation between a loss in the low energy spectral weight due to the pseudogap and a decrease of the coherent fraction of paired electrons. Therefore, the pseudogap competes with the superconductivity by depleting the spectral weight available for pairing in the region of momentum space where the superconducting gap is largest. This leads to a very unusual state in the underdoped cuprates, where only part of the Fermi surface develops coherence.