Descripción del proyecto
Un nuevo diseño experimental para examinar la dinámica electrónica a escalas diminutas
El proyecto UpTEMPO, financiado con fondos europeos, prevé desarrollar instrumentos ultrarrápidos basados en láser para estudiar el funcionamiento interno de los materiales. La gran velocidad de los impulsos láser inducirá corrientes a través de las muestras, permitiendo a los investigadores estudiar el comportamiento y la dinámica de los electrones en nanoestructuras y moléculas. El éxito del proyecto se basará en establecer nuevos experimentos en el punto de encuentro de la óptica ultrarrápida y la microscopía de sonda de barrido. La comprensión exhaustiva de los mecanismos que determinan las propiedades de la materia podría ayudar en el diseño de materiales avanzados para un amplio espectro de aplicaciones.
Objetivo
The project aims at imaging electronic dynamics in molecules with atomic precision and sub-femtosecond temporal resolution. This result will be achieved by establishing new experiments at the boundary of ultrafast optics and scanning probe microscopy where the electric field of single-cycle light pulses is harnessed to control currents in nanojunctions. The basic concept relies on the fact that state-of-the-art femtosecond optical wave packets exhibit only one cycle of radiation with a defined electric field maximum. These pulses need to be phase locked to a “cosine-like” electric field profile. If such radiation is focused onto a junction with a nonlinear current-voltage characteristics, a net charge flow results solely due to the bias induced by the optical field.
In detail, we want to exploit the time resolution provided by this new technique and induce electron transport at the probe tip of a scanning tunneling microscope (STM). The optical control of the current over a sub-optical-cycle interval will guarantee a temporal resolution better that one femtosecond, thus improving by several orders of magnitude what can be achieved with standard electronic bias.
The core of the experimental system will be an ultrabroadband and passively phase-locked Er:fiber laser that is designed to generate single-cycle optical pulses in the near/mid-infrared, i.e. off resonant to the transition energies of III-V and II-VI semiconductors and large molecules. This laser will operate at 80-MHz repetition rate for enhanced sensitivity and stability when coupled to an ultra-high-vacuum STM. The setup will allow for the direct combination of independent pulse trains to resonantly excite few-femtosecond dynamics and then probe the electron density via the optically driven tunneling. In this pump-probe scheme it will be possible to map with atomic resolution the coherent evolution of electronic wavefunctions that in molecules and nanosystems follows an impulsive photoexcitation.
Ámbito científico
Palabras clave
Programa(s)
Régimen de financiación
ERC-COG - Consolidator GrantInstitución de acogida
4365 ESCH-SUR-ALZETTE
Luxemburgo