Department of Physics, Graduate School of Engineering , Yokohama National University , Yokohama 240-8501 , Japan.
Central Research Laboratory , Hamamatsu Photonics K.K. , 5000 Hirakuchi, Hamakita , Hamamatsu City , Shizuoka 434-8601 , Japan.
Nano Lett. 2018 Aug 8;18(8):5198-5204. doi: 10.1021/acs.nanolett.8b02161. Epub 2018 Jul 25.
Light-field-driven processes occurring under conditions far beyond the diffraction limit of the light can be manipulated by harnessing spatiotemporally tunable near fields. A tailor-made carrier envelope phase in a tunnel junction formed between nanogap electrodes allows precisely controlled manipulation of these processes. In particular, the characterization and active control of near fields in a tunnel junction are essential for advancing elaborate manipulation of light-field-driven processes at the atomic-scale. Here, we demonstrate that desirable phase-controlled near fields can be produced in a tunnel junction via terahertz scanning tunneling microscopy (THz-STM) with a phase shifter. Measurements of the phase-resolved subcycle electron tunneling dynamics revealed an unexpected large carrier-envelope phase shift between far-field and near-field single-cycle THz waveforms. The phase shift stems from the wavelength-scale feature of the tip-sample configuration. By using a dual-phase double-pulse scheme, the electron tunneling was coherently manipulated over the femtosecond time scale. Our new prescription-in situ tailoring of single-cycle THz near fields in a tunnel junction-will offer unprecedented control of electrons for ultrafast atomic-scale electronics and metrology.
光场驱动的过程在远远超出光的衍射极限的条件下发生，可以通过利用时空可调的近场来操纵。在纳米间隙电极之间形成的隧道结中，定制的载波包络相位允许对这些过程进行精确控制。特别是，隧道结中近场的特性和主动控制对于推进原子尺度上光场驱动过程的精细操纵至关重要。在这里，我们通过太赫兹扫描隧道显微镜（THz-STM）与相移器证明了在隧道结中可以产生期望的相控近场。对相分辨亚周期电子隧穿动力学的测量揭示了远场和近场单周期太赫兹波形之间出乎意料的大载波包络相位差。相位差源于尖端-样品配置的波长尺度特征。通过使用双相双脉冲方案，可以在飞秒时间尺度上对电子隧穿进行相干操纵。我们在隧道结中对单周期太赫兹近场进行原位定制的新方案将为超快原子尺度电子学和计量学提供前所未有的电子控制。
