arXiv subjects

Man Tou Wong

Publications and source records attributed to Man Tou Wong.

3 recordsLinked to original sources

arXiv2026

Ultrafast non-thermal suppression of ferroelectricity by carrier screening in LiNbO3

Ferroelectric materials are key to energy-efficient electronics, memory, and optical applications. While charge carriers typically screen and suppress ferroelectricity, their role under nonequilibrium conditions remains elusive. Here, we use femtosecond laser pulses to liberate trapped carriers in LiNbO3 and track the response using time-resolved second-harmonic generation and stimulated Raman scattering. Even dilute photoexcited carriers induce a rapid yet enduring suppression of polarization and Raman susceptibility. Fluence- and temperature-dependent analyses confirm the suppression is non-thermal and arises from transient carrier screening. These findings reveal an efficient, reversible, and symmetry-preserving mechanism to modulate ferroelectricity on ultrafast timescales, offering a new route to control ferroic and competing quantum phases.

cond-mat.mtrl-sci↗

arXiv2024

Terahertz stimulated parametric downconversion of a magnon mode in an antiferromagnet

In condensed matter systems, interactions between collective modes offer avenues for nonlinear coherent manipulation of coupled excitations and quantum phases. Antiferromagnets, with their inherently coupled magnon modes, provide a promising platform for nonlinear control of microscopic spin waves and macroscopic magnetization. However, nonlinear magnon-magnon interactions have been only partially elaborated, leaving key gaps in the prospects for potential ultrahigh-bandwidth magnonic signal processing. Here, we use a pair of intense terahertz pulses to sequentially excite two distinct coherent magnon modes in an antiferromagnet and find that the magnon mode with a lower frequency undergoes amplification when the higher-frequency mode is driven. We unveil the nonlinear excitation pathways of this stimulated parametric downconversion process by using polarization-selective two-dimensional terahertz spectroscopy. Our work provides fundamental insights into nonlinear magnonics in antiferromagnets, laying the groundwork for forthcoming spintronic and magnonic devices based on nonlinear magnon-magnon interactions.

cond-mat.mtrl-sci↗

arXiv2024

Terahertz field-induced nonlinear coupling of two magnon modes in an antiferromagnet

Magnons are quantized collective spin-wave excitations in magnetically ordered materials. Revealing their interactions among these collective modes is crucial for the understanding of fundamental many-body effects in such systems and the development of high-speed information transport and processing devices based on them. Nevertheless, identifying couplings between individual magnon modes remains a long-standing challenge. Here, we demonstrate spectroscopic fingerprints of anharmonic coupling between distinct magnon modes in an antiferromagnet, as evidenced by coherent photon emission at the sum and difference frequencies of the two modes. This discovery is enabled by driving two magnon modes coherently with a pair of tailored terahertz fields and then disentangling a mixture of nonlinear responses with different origins. Our approach provides a route for generating nonlinear magnon-magnon mixing.

cond-mat.mtrl-sci↗