Electrets are dielectric materials that have a quasi-permanent dipole polarization. A single-molecule electret is a long-sought-after nanoscale component because it can lead to miniaturized non-volatile memory storage devices. The signature of a single-molecule electret is the switching between two electric dipole states by an external electric field. The existence of these electrets has remained controversial because of the poor electric dipole stability in single molecules. Here we report the observation of a gate-controlled switching between two electronic states in Gd@C₈₂. The encapsulated Gd atom forms a charged centre that sets up two single-electron transport channels. A gate voltage of ±11 V (corresponding to a coercive field of ~50 mV Å^–1) switches the system between the two transport channels with a ferroelectricity-like hysteresis loop. Using density functional theory, we assign the two states to two different permanent electrical dipole orientations generated from the Gd atom being trapped at two different sites inside the C₈₂ cage. The two dipole states are separated by a transition energy barrier of 11 meV. The conductance switching is then attributed to the electric-field-driven reorientation of the individual dipole, as the coercive field provides the necessary energy to overcome the transition barrier.

驻极体是具有准永久偶极极化的介电材料。单分子驻极体是备受追捧的纳米级组件，因为它可以导致小型化的非易失性存储设备。单分子驻极体的特征是通过外部电场在两个电偶极状态之间进行切换。这些驻极体的存在一直存在争议，因为单个分子的电偶极稳定性差。在这里，我们报告了在Gd @ C _82中两个电子状态之间的门控切换的观察结果。封装的Gd原子形成一个带电中心，该中心建立了两个单电子传输通道。栅极电压为±11 V（对应于〜50 mVÅ ^–1的矫顽场）通过类似铁电的磁滞回线在两个传输通道之间切换系统。使用密度泛函理论，我们将两种状态分配给两个不同的永久性电偶极子方向，这些方向是由Gd原子在C ₈₂笼子内部的两个不同位置捕获而产生的。两个偶极子状态之间的过渡能量势垒为11 meV。然后，电导率切换归因于单个偶极子的电场驱动的重新定向，因为矫顽场提供了克服跃迁势垒所需的能量。