Enhanced interlayer coupling and slowed carrier relaxation in MXene (Ti3C2Tx) under hydrostatic pressure

MXene materials hold great promise for flexible pressure-sensing applications; however, the evolution of their carrier transport and energy relaxation processes under external pressure remains poorly understood. In this work, we systematically investigate the photoexcited ultrafast dynamics of the prototypical MXene Ti3C2Tx under hydrostatic pressures ranging from 0.7 to 6.4 kbar. Our results reveal that with increasing pressure, the relaxation of the excited-state absorption peak centered at ∼520 nm is significantly retarded, manifested by a monotonic increase in both the electron–electron scattering time (τ1) and the electron–phonon scattering time (τ2). The counterintuitive pressure-induced slowdown of carrier relaxation finds its origin in the synergistic effects of enhanced inter-flake charge hopping, reduced carrier densities, and weakened electron–phonon coupling. Furthermore, the accelerated relaxation of the plasmon bleach peak with increasing pressure provides direct evidence for improved lattice cooling efficiency due to weakened electron–phonon coupling and enhanced interlayer thermal diffusion. Collectively, our findings establish a microscopic physical picture of pressure-modulated interlayer coupling and ultrafast dynamics in MXenes, offering new experimental benchmarks and providing a microscopic foundation for the understanding of pressure-sensing mechanisms in MXene-based devices.