Pseudo Jahn-Teller effect driven displacive ferroelectric transition in GeTe
Phys. Rev. Materials 10, 084408 – Published 25 August, 2026
DOI: https://doi.org/10.1103/w7ll-dsct
Abstract
Unifying local and average structural descriptions in germanium telluride (GeTe) remains a critical challenge, highlighting the long-standing displacive versus order-disorder debate in ferroelectric crystals. In this work, we investigate the real-time atomic dynamics and local structural fluctuations in GeTe by coupling density functional theory (DFT) with large-scale molecular dynamics (MD) simulations driven by neuroevolution potentials (NEPs). Our findings demonstrate a displacive ferroelectric phase transition near the tricritical point. By encompassing the spatial correlation length, our mesoscale simulations overcome finite-size effects that can induce multistate hopping artifacts. Crucially, the computed longitudinal current correlation function lacks a quasielastic peak, effectively ruling out thermally activated discrete jumps. Furthermore, time-resolved Crystal Orbital Hamilton Population (tr-COHP) analysis reveals a femtosecond “seesaw” charge transfer driven by the pseudo-Jahn-Teller effect (PJTE). The apparent local disorder in the cubic phase originates from continuous, large-amplitude anharmonic vibrations on a remarkably flat adiabatic potential energy surface, rather than static multiwell hopping. These results support a “macro-ordered yet micro-disordered” displacive paradigm, providing fundamental insights for rationalizing and tailoring the thermal and optoelectronic properties of IV-VI compounds.
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Machine Learning for Materials Discovery and Understanding
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