We study a dimerized spin-1/2 chain, such as ${\mathrm{CuGeO}}_3$, hosting triplon excitations coupled to optical phonons under weak terahertz laser driving. Both phonons and triplons weakly lose energy into the surrounding baths, forming a nonequilibrium steady state. In the strong phonon-triplon coupling regime, phonons near the two-triplon continuum hybridize strongly with triplons. Using mean-field Lindblad dynamics, we show that strong hybridization induces sharp first-order phase transitions—either single or simultaneous double—in the emission spectrum, mainly due to nonlinearities in the chain and the instantaneous breaking of spatial inversion symmetry, as captured by the phonon displacement. Using mean-field Floquet analysis of harmonic modes in both sectors, we analytically confirm the existence of these phase transitions. Furthermore, we map the complete steady-state phase diagram by varying key control parameters and provide experimentally relevant parameters for observing these transitions in laser-driven ${\mathrm{CuGeO}}_3$.

Close

PrevNext

View figure in article

• Dissipative dynamics
• Dynamical phase transitions
• Light-matter interaction
• Magnetism
• Optical bistability
• Optical phonons
• Phonons
• Spin dynamics
• Spin-phonon coupling
• Triplon
• Inversion symmetry
• Spin chains
• Terahertz techniques
• Ultrafast pump-probe spectroscopy