Vibrational properties of CuInP2S6 across the ferroelectric transition
Vibrational properties of CuInP2S6 across the ferroelectric transition
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DOI：
10.1103/physrevb.105.075151
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发表时间：
2022-02-28
影响因子：
3.7
通讯作者：
Musfeldt, Janice L.
中科院分区：
文献类型：
--
作者：
Neal, Sabine N.;Singh, Sobhit;Musfeldt, Janice L.
为了探索双亚晶格铁电的性质，我们测量了CuInP2S6在铁电和玻璃态转变中的红外和拉曼散射响应，并将我们的发现与对称性分析、相稳定性计算和晶格动力学进行了比较。除了发现位移特征和围绕铁电转变温度T-C的大滞后区域外，我们还确定了稳定极性相的振动模式，并确认了两种相反极化的铁电变体的存在。在T-C以下，T-g处的弛豫或玻璃化转变的特征是局部结构的变化，其形式是微妙的峰移和低频面外含cu和in模式的激活。后者是由于Cu/ in配位环境的变化和相关的有序-无序过程。此外，Tg分两步发生，具有较大的滞后区和明显的底层散射。结合室温相分离成像，为在超薄极限下研究CuInP2S6薄膜奠定了基础。
In order to explore the properties of a two-sublattice ferroelectric, we measured the infrared and Raman scattering response of CuInP2S6 across the ferroelectric and glassy transitions and compared our findings to a symmetry analysis, calculations of phase stability, and lattice dynamics. In addition to uncovering displacive character and a large hysteresis region surrounding the ferroelectric transition temperature T-C, we identify the vibrational modes that stabilize the polar phase and confirm the presence of two ferroelectric variants with opposite polarizations. Below T-C, a poorly understood relaxational or glassy transition at T-g is characterized by local structure changes in the form of subtle peak shifting and activation of low frequency out-of-plane Cu-and In-containing modes. The latter are due to changes in the Cu/In coordination environments and associated order-disorder processes. Moreover, Tg takes place in two steps with another large hysteresis region and significant underlying scattering. Combined with imaging of the room temperature phase separation, this effort lays the groundwork for studying CuInP2S6 under external stimuli and in the ultrathin limit.