arXiv subjects

M. Basini

Publications and source records attributed to M. Basini.

5 recordsLinked to original sources

arXiv2026

THz-induced phonomagnetism in diamagnetic quantum paraelectric KTaO$_3$

The current efforts striving to develop new ways of data manipulation are aimed at ultrafast control of magnetization in magnetic materials, as well as at inducing magnetic moments in diamagnetics. We demonstrate that in the diamagnetic quantum paraelectric KTaO$_3$, the electric field of circularly polarized THz pulses with an amplitude of $\sim 300\,$kV/cm induces a transient magnetic-like response by resonantly exciting its degenerate soft polar phonon. This phonon-mediated response was measured using the THz pump---optical probe technique via the time-resolved magneto-optic Faraday effect. Our detection scheme was set up to cancel out the major part of the electro-optic Kerr effect which also usually significantly contributes to the transient response. The Kerr-effect-related signal was further suppressed by subtracting the experimental data related to oppositely circularly polarized THz radiation. Thus, we were able to unambiguously identify a temperature-dependent magnetic-like behavior of the KTaO$_3$ crystal manifested by the extracted Faraday rotation. We developed a theoretical model describing well quantitatively the measured curves of the transient Faraday effect signal. However, their amplitudes exhibit an unexpected temperature dependence, which might be a key to a deeper understanding of the observed phonomagnetic effect.

cond-mat.mtrl-sci↗

arXiv2024

Terahertz-driven parametric excitation of Raman-active phonons in LaAlO$_{3}$

Achieving parametric excitation in an oscillating physical system involves periodically adjusting one of its parameters to modulate the oscillator's natural frequency. This phenomenon has been observed in numerous systems within physics and engineering, profoundly transforming modern science and technology. Despite rapid progress, the parametric control of collective excitations, such as phonons, remains a challenge while promising to generate novel and intriguing effects in a largely unexplored field. Here, we investigate the terahertz (THz) field-induced dynamics of Raman-active phonons in the perovskite structure of LaAlO$_3$ (LAO). Utilizing intense THz pulses, we demonstrate a novel mechanism of parametric phonon excitation marked by substantial subharmonic components. Theoretical analysis can successfully capture the hallmarks of the observed phenomena in a physical scenario with the THz field inducing a parametric coupling between the Raman mode and pairs of acoustic phonon excitations.

cond-mat.mtrl-sci↗

arXiv2024

Ultrafast terahertz field control of the emergent magnetic and electronic interactions at oxide interfaces

Ultrafast electric-field control of emergent electronic and magnetic states at oxide interfaces offers exciting prospects for the development of new generations of energy-efficient devices. Here, we demonstrate that the electronic structure and emergent ferromagnetic interfacial state in epitaxial LaNiO3/CaMnO3 superlattices can be effectively controlled using intense single-cycle THz electric-field pulses. We employ a combination of polarization-dependent X-ray absorption spectroscopy with magnetic circular dichroism and X-ray resonant magnetic reflectivity to measure a detailed magneto-optical profile and thickness of the ferromagnetic interfacial layer. Then, we use time-resolved and temperature-dependent magneto-optical Kerr effect, along with transient optical reflectivity and transmissivity measurements, to disentangle multiple correlated electronic and magnetic processes driven by ultrafast high-field (~1 MV/cm) THz pulses. These processes include an initial sub-picosecond electronic response, consistent with non-equilibrium Joule heating; a rapid (~270 fs) demagnetization of the ferromagnetic interfacial layer, driven by THz-field-induced nonequilibrium spin-polarized currents; and subsequent multi-picosecond dynamics, possibly indicative of a change in the magnetic state of the superlattice due to the transfer of spin angular momentum to the lattice. Our findings shed light on the intricate interplay of electronic and magnetic phenomena in this strongly correlated material system, suggesting a promising avenue for efficient control of two-dimensional ferromagnetic states at oxide interfaces using ultrafast electric-field pulses.

cond-mat.mtrl-sci↗

arXiv2022

Terahertz electric-field driven dynamical multiferroicity in SrTiO$_3$

The emergence of collective order in matter is among the most fundamental and intriguing phenomena in physics. In recent years, the ultrafast dynamical control and creation of novel ordered states of matter not accessible in thermodynamic equilibrium is receiving much attention. Among those, the theoretical concept of dynamical multiferroicity has been introduced to describe the emergence of magnetization by means of a time-dependent electric polarization in non-ferromagnetic materials. In simple terms, a large amplitude coherent rotating motion of the ions in a crystal induces a magnetic moment along the axis of rotation. However, the experimental verification of this effect is still lacking. Here, we provide evidence of room temperature magnetization in the archetypal paraelectric perovskite SrTiO$_3$ due to this mechanism. To achieve it, we resonantly drive the infrared-active soft phonon mode with intense circularly polarized terahertz electric field, and detect a large magneto-optical Kerr effect. A simple model, which includes two coupled nonlinear oscillators whose forces and couplings are derived with ab-initio calculations using self-consistent phonon theory at a finite temperature, reproduces qualitatively our experimental observations on the temporal and frequency domains. A quantitatively correct magnitude of the effect is obtained when one also considers the phonon analogue of the reciprocal of the Einsten - de Haas effect, also called the Barnett effect, where the total angular momentum from the phonon order is transferred to the electronic one. Our findings show a new path for designing ultrafast magnetic switches by means of coherent control of lattice vibrations with light.

cond-mat.str-el↗

arXiv2021

Ultrafast amplification and non-linear magneto-elastic coupling of coherent magnon modes in an antiferromagnet

We investigate the role of domain walls in the ultrafast magnon dynamics of an antiferromagnetic NiO single crystal in a pump-probe experiment with variable pump photon energy. Analysing the amplitude of the energy-dependent photo-induced ultrafast spin dynamics, we detect a yet unreported coupling between the material's characteristic THz- and a GHz-magnon modes. We explain this unexpected coupling between two orthogonal eigenstates of the corresponding Hamiltonian by modelling the magneto-elastic interaction between spins in different domains. We find that such interaction, in the non-linear regime, couples the two different magnon modes via the domain walls and it can be optically exploited via the exciton-magnon resonance.

cond-mat.other↗