Colossal Terahertz Nonlinearity in Angstrom- and Nanometer-Sized Gaps
- Authors
- Han, Sanghoon; Kim, Joon-Yeon; Kang, Taehee; Bahk, Young-Mi; Rhie, Jiyeah; Kang, Bong Joo; Kim, Yong Seung; Park, Joohyun; Kim, Won Tae; Jeon, Hyeongtag; Roterrnund, Fabian; Kim, Dai-Sik
- Issue Date
- Aug-2016
- Publisher
- AMER CHEMICAL SOC
- Keywords
- terahertz nonlinearity; quantum tunneling; angstrom gap; metal-insulator-metal; graphene; aluminum oxide
- Citation
- ACS PHOTONICS, v.3, no.8, pp.1440 - 1445
- Indexed
- SCIE
SCOPUS
- Journal Title
- ACS PHOTONICS
- Volume
- 3
- Number
- 8
- Start Page
- 1440
- End Page
- 1445
- URI
- https://scholarworks.bwise.kr/hanyang/handle/2021.sw.hanyang/22277
- DOI
- 10.1021/acsphotonics.6b00103
- ISSN
- 2330-4022
- Abstract
- We investigated optical nonlinearity induced by electron tunneling through an insulating vertical gap between metals, both at terahertz frequency and at near-infrared frequency. We adopted graphene and alumina layers as gap materials to form gap widths of 3 angstrom and 1.5 nm, respectively. Transmission measurements show that tunneling-induced transmittance changes from strong fields at the gaps can be observed with relatively weak incident fields at terahertz frequency due to high field enhancement, whereas nonlinearity at the near-infrared frequency is restricted by laser-induced metal damages. Even when the same level of tunneling currents occurs at both frequencies, transmittance in the terahertz regime decreases much faster than that in the near-infrared regime. An equivalent circuit model regarding the tunneling as a resistance component reveals that strong terahertz nonlinearity is due to much smaller displacement currents relative to tunneling currents, also explaining small nonlinearity of the near-infrared regime with orders of magnitude larger displacement currents.
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