Recently, Song et al [Nature 462, 1039 (2009)] employed transition-voltage spectroscopy to demonstrate that the energy $\varepsilon_H$ of the highest occupied molecular orbital (HOMO) of single-molecule transistors can be controlled by a gate potential $V_G$. To demonstrate the linear dependence $\varepsilon_H-V_G$, the experimental data have been interpreted by modeling the molecule as an energy barrier spanning the spatial source-drain region of molecular junctions. Since, as shown in this work, that crude model cannot quantitatively describe the measured $I$-$V$-characteristics, it is important to get further support for the linear dependence of $\varepsilon_H$ on $V_G$. The results presented here, which have been obtained within a model of a point-like molecule, confirm this linear dependence. Because the two models rely upon complementary descriptions, the present results indicate that the interpretation of the experimental results as evidence for a gate controlled HOMO is sufficiently general.
Depth Profiling of Oxygen Migration in Ta/HfO2 Stacks During Ionic Liquid Gating
Institute of Physics, Johannes Gutenberg University Mainz（美因茨约翰内斯·古腾堡大学物理研究所）；Faculty of Physics, Bielefeld University（比勒费尔德大学物理学院）；Faculty of Physics, Osnabrück University（奥斯纳布吕克大学物理学院）
Mapping the chemical potential dependence of current-induced spin polarization in a topological insulator
我们报告了在拓扑绝缘体器件中电流诱导的表面电流自旋极化的电测量，其中体导电和表面导电的贡献可以通过电门来解开。该器件使用铁磁隧道结（坡莫合金/Al 2 O3）作为背栅（Bi，Sb）2 Te 3通道上的自旋检测器。我们观察到滞后电压信号的检测器铁磁体的磁化切换平行或反平行的自旋极化的表面电流。检测到的电压变化的幅度与（Bi，Sb）2 Te 3通道中施加的DC偏置电流成线性比例。由于化学势从体能带调谐到表面态能带，我们观察到静电门控范围内自旋相关电压的增强高达300%。使用一个简单的模型，我们提取的自旋极化附近的电荷中性（即狄拉克点）。
Giant Voltage Manipulation of MgO-based Magnetic Tunnel Junctions via Localized Anisotropic Strain: a Potential Pathway to Ultra-Energy-Efficient Memory Technology
在压电/铁磁系统中，应变介导的磁化电压控制是实现节能自旋电子存储器件的一种有前途的机制。在这里，我们展示了巨大的电压操纵的MgO磁性隧道结（MTJ）上的Pb（Mg 1/3 Nb 2/3）0.7Ti 0.3O3（PMN-PT）压电基板（001）取向。据发现，磁易轴，开关场，和隧道磁阻（TMR）的MTJ可以有效地控制应变从下面的压电层时，施加的栅极电压。可重复的电压控制的MTJ之间的高/低电阻状态的切换被证明。更重要的是，而不是依赖于压电基板的固有各向异性，以产生所需的应变，我们利用各向异性应变产生的局部选通方案，这是可扩展的，并服从实际的存储器应用。另外，在压电层上采用基于晶体MgO的MTJ使其本身在应变介导MRAM器件中具有高TMR。
