Two-color field enhancement at an STM junction for spatiotemporally resolved photoemission
- Columbia Univ., New York, NY (United States)
- Columbia Univ., New York, NY (United States); Univ. of Michigan, Ann Arbor, MI (United States)
- Brookhaven National Lab. (BNL), Upton, NY (United States); The Univ. of Texas at Austin, Austin, TX (United States)
- Brookhaven National Lab. (BNL), Upton, NY (United States); Univ. of Nebraska, Lincoln, NE (United States)
- Brookhaven National Lab. (BNL), Upton, NY (United States)
Here, we report measurements and numerical simulations of ultrafast laser-excited carrier flow across a scanning tunneling microscope (STM) junction. The current from a nanoscopic tungsten tip across a ~1 nm vacuum gap to a silver surface is driven by a two-color excitation scheme that uses an optical delay-modulation technique to extract the two-color signal from background contributions. The role of optical field enhancements in driving the current is investigated using density functional theory and full three-dimensional finite-difference time-domain computations. We find that simulated field-enhanced two-photon photoemission (2PPE) currents are in excellent agreement with the observed exponential decay of the two-color photoexcited current with increasing tip–surface separation, as well as its optical-delay dependence. The results suggest an approach to 2PPE with simultaneous subpicosecond temporal and nanometer spatial resolution.
- Research Organization:
- Brookhaven National Laboratory (BNL), Upton, NY (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC), Basic Energy Sciences (BES)
- Grant/Contract Number:
- SC0012704; AC02-98CH10886; FG02-90ER14104
- OSTI ID:
- 1409641
- Alternate ID(s):
- OSTI ID: 1367373
- Report Number(s):
- BNL-114695-2017-JA; OPLEDP; R&D Project: CO007; KC0301050
- Journal Information:
- Optics Letters, Vol. 42, Issue 13; ISSN 0146-9592
- Publisher:
- Optical Society of America (OSA)Copyright Statement
- Country of Publication:
- United States
- Language:
- English
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