Park Dongsung T, Lee Seokyeong, Kim Uhjin, Choi Hyoungsoon, Choi Hyung Kook
Department of Physics, KAIST, Daejeon, 34141, Republic of Korea.
Department of Physics, Research Institute of Physics and Chemistry, Jeonbuk National University, Jeonju, 54896, Republic of Korea.
Sci Rep. 2020 Nov 12;10(1):19746. doi: 10.1038/s41598-020-76790-z.
Quantum point contacts (QPC) are a primary component in mesoscopic physics and have come to serve various purposes in modern quantum devices. However, fabricating a QPC that operates robustly under extreme conditions, such as high bias or magnetic fields, still remains an important challenge. As a solution, we have analyzed the trench-gated QPC (t-QPC) that has a central gate in addition to the split-gate structure used in conventional QPCs (c-QPC). From simulation and modelling, we predicted that the t-QPC has larger and more even subband spacings over a wider range of transmission when compared to the c-QPC. After an experimental verification, the two QPCs were investigated in the quantum Hall regimes as well. At high fields, the maximally available conductance was achievable in the t-QPC due to the local carrier density modulation by the trench gate. Furthermore, the t-QPC presented less anomalies in its DC bias dependence, indicating a possible suppression of impurity effects.
量子点接触（QPC）是介观物理学中的主要元件，并已在现代量子器件中用于各种目的。然而，制造在诸如高偏置或磁场等极端条件下仍能稳健运行的QPC仍然是一项重大挑战。作为一种解决方案，我们分析了沟槽栅控量子点接触（t-QPC），它除了具有传统量子点接触（c-QPC）中使用的分裂栅结构外，还具有一个中央栅极。通过模拟和建模，我们预测，与c-QPC相比，t-QPC在更宽的传输范围内具有更大且更均匀的子带间距。经过实验验证后，还对这两种量子点接触在量子霍尔区域进行了研究。在高场下，由于沟槽栅极对局部载流子密度的调制，t-QPC能够实现最大可用电导。此外，t-QPC在其直流偏置依赖性方面表现出较少的异常，表明可能抑制了杂质效应。
