Rice University

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Seminar

Electrical and Computer Engineering
Dean of Engineering
Faculty Host: Jun Kono

Speaker: Ikufumi Katayama
Professor of Engineering
Yokohama National University

ECE Seminar Series: Terahertz-field-induced tunneling for future applications including ultrafast scanning tunneling microscope (698/699)

Tuesday, March 28, 2017
2:00 PM  to 3:00 PM

300  Brockman Hall for Physics
Rice University
6100 Main St
Houston, Texas, USA

Field-induced-tunneling has been an important ingredient for many kinds of electronic devices and optical nonlinear phenomena. However, when we use DC field or near-infrared light field, it is rather difficult to understand the dynamical behaviors because of its non-perturbative nature and the possible damage because the field strength required for tunneling is nearly equal to the damage threshold of the materials and devices. Here, we will show that combination of terahertz electric field with narrow gap semimetals and metal nano-structures offers an interesting playground to investigate such tunneling dynamics without causing damage on the sample. This combination will also be applicable to promising ultrafast scanning tunneling microscope, which may be useful for revealing ultrafast dynamics of the nanoscale materials. In the experiment, we generated an intense terahertz waves via tilted-pulse front technique, and the generated single cycle pulse have a maximum electric field of about 300 kV/cm. This field strength is enough to induce many kinds of nonlinearity in materials. We first apply this pulse to a single crystalline film of semimetal Bismuth, and the field induced transparency is observed. This could be understood as a result of Dirac band dispersion in Bismuth. When we apply it to the percolated Au film, we observed the field induced absorption due to the electron tunneling through nano-gaps in the film. Finally, we demonstrate that this terahertz field induced tunneling can be controlled by the carrier envelope phase (CEP) of the terahertz pulse. Electrons can be injected into or retracted from a sample via CEP, which could be very useful for future ultrafast nanoscopy using terahertz scanning tunneling microscope.

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