Terahertz-induced Fermi resonance

• Applicant: Evgeny Mashkovich, Ph.D.
• Subject Area: Experimental Condensed Matter Physics
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 548126838

In many cases, strong nonlinearity between spin and/or lattice eigen states arises due to intense external stimuli and causes energy flow between these eigenstates. In contrast, I propose a novel approach utilizing a Fermi resonance to induce nonlinear coupling between distinct magnonic and/or phononic eigenstates. Remarkably, the strength of nonlinear energy flow between eigenstates in this case is controlled by adjusting the frequency matching conditions. A Fermi resonance occurs when the frequency ratio between two eigenstates, w2/w1, is approximately 1:2, and leads to a significant enhancement of the nonlinear coupling between these eigenstates. Consequently, by adjusting the frequency of an eigenstate through external factors such as temperature, external magnetic field, or chemical stress, my intention is to systematically regulate the transfer of energy from one eigenstate to another in a coherent manner. This approach holds the potential to significantly advance our comprehension of coupled dynamics, surpassing the limitations of the conventional three-temperature model. To realize this ambitious objective, time-resolved coupled dynamics will be investigated using state-of-the-art terahertz spectroscopy techniques, with a particular emphasis on two-dimensional (2D) spectroscopy which is intrinsically sensitive to nonlinear coupled dynamics.

• DFG Programme: Research Grants