Sorry, my yesterday's reply is not submitted successfully.
From your results, it is clear that the enhavement is inside the nano particle instead of at the gap of the tips. This means the excitation is not correct, or the device configuration is not correct. You can use log scale to check the field intensity at the gap. Such device needs careful design. unfortuately it is not that obvious whe things are changed. Please take some time to optimize the device configuration.
I guess it is due to the whipser gallery modes inside each triangle. Due to symmetry effect, the location of such modes cannot be uniquely positioned, probably due to excitation. Such personal observation is purely for your reference.
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