Externally triggerable optical pump-probe scanning tunneling microscopy

Optical pump-probe scanning tunneling microscopy (OPP-STM) has enabled the measurement of ultrafast dynamics in real space. However, the use of a pulse picker to extract selected laser pulses to realize delay-time modulation, which efficiently suppresses the thermal expansion problems, limits the availability of time-resolved measurement. Here, we present a more applicable type of OPP-STM that we have developed. Two externally triggerable pulse lasers were used to produce pump and probe pulses, and wide-range delay-time modulation was simply realized by adjusting the timing of the pulses. The performance of this new type of OPP-STM was demonstrated by measuring the carrier dynamics in WSe2. (C) 2019 The Japan Society of Applied Physics