Coherent Transfer of Lattice Entropy via Extreme Nonlinear Phononics in Metal Halide Perovskites
arxiv(2024)
摘要
Entropy transfer in metal halide perovskites, characterized by significant
lattice anharmonicity and low stiffness, underlies the remarkable properties
observed in their optoelectronic applications, ranging from solar cells to
lasers. The conventional view of this transfer involves stochastic processes
occurring within a thermal bath of phonons, where lattice arrangement and
energy flow from higher to lower frequency modes. Here we unveil a
comprehensive chronological sequence detailing a conceptually distinct,
coherent transfer of entropy in a prototypical perovskite CH_3NH_3Pbl_3.
The terahertz periodic modulation imposes vibrational coherence into electronic
states, leading to the emergence of mixed (vibronic) quantum beat between
approximately 3 THz and 0.3 THz. We highlight a well-structured, bi-directional
time-frequency transfer of these diverse phonon modes, each developing at
different times and transitioning from high to low frequencies from 3 to 0.3
THz, before reversing direction and ascending to around 0.8 THz.
First-principles molecular dynamics simulations disentangle a complex web of
coherent phononic coupling pathways and identify the salient roles of the
initial modes in shaping entropy evolution at later stages. Capitalizing on
coherent entropy transfer and dynamic anharmonicity presents a compelling
opportunity to exceed the fundamental thermodynamic (Shockley-Queisser) limit
of photoconversion efficiency and to pioneer novel optoelectronic
functionalities.
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