${\ m{EuTe}}_{4}$中的多层选择性极化电荷密度波
Multiple Layer-Selective Polar Charge Density Waves in ${\rm{EuTe}}_{4}$
AI总结：
本研究通过第一性原理计算揭示${\ m{EuTe}}_{4}$中存在多层选择性极化电荷密度波，并通过电场和光场调控实现非易失态切换。
摘要：
${\ m{EuTe}}_{4}$是一种极化电荷密度波（CDW）材料，具有在电场和光场下表现出巨热滞回和非易失态切换的特性，近年来引起了广泛关注。然而，这些异常现象的深入理解仍然不足。本文通过第一性原理计算揭示，${\ m{EuTe}}_{4}$中的极化CDW状态具有新的层选择性性质，其中多个能量相近的CDW构型共存并表现出低的相互转换能垒。蒙特卡罗模拟表明，${\ m{EuTe}}_{4}$中的巨热滞回源于由构型熵变化主导的相变，该相变过程中材料表现出具有多种局部极化构型的亚稳CDW状态，这些构型破坏了垂直方向的平移对称性。该亚稳CDW状态的构型组成可通过电场和光场有效调控，从而实现非易失态切换。我们的理论发现与最近${\ m{EuTe}}_{4}$中的实验观测一致，并为探索多层系统中极化CDW的新兴现象和应用铺平了道路。
英文摘要：
${\rm{EuTe}}_{4}$ is a polar charge density wave (CDW) material, with giant thermal hysteresis and non-volatile state switching under electric and optical fields, attracting great attention in recent years. However, the in-depth understanding of these anomalous phenomena remains elusive. Herein, via first-principles calculations, we reveal that the polar CDW state in ${\rm{EuTe}}_{4}$ hosts a novel layer-selective nature, wherein multiple energetically close CDW configurations coexist and exhibit low interconversion energy barriers. Monte Carlo simulations indicate that the giant thermal hysteresis in ${\rm{EuTe}}_{4}$ originates from a phase transition mainly driven by the change of configurational entropy, around which the material hosts a metastable CDW state characterized by diverse local polar configurations breaking the out-of-plane translational symmetry. The configurational composition of this metastable CDW state can be effectively controlled by electric and optical fields, thereby enabling non-volatile state switching. Our theoretical findings align well with recent experimental observations in ${\rm{EuTe}}_{4}$ and pave the way for exploring the emerging phenomena and applications of polar CDW in multilayered systems.
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