Time, momentum, and energy resolved pump probe tunneling spectroscopy of the nonequilibrium electrons in a Landau level (part 1).*

Spectroscopy of nonequilibrium systems can uncover intricate relaxation mechanisms and short-lived metastable states that are hidden in strongly correlated materials. Here, we developed a novel time, momentum, and energy resolved pump-probe tunneling spectroscopy (Tr-MERTS) that allows visualization of nonequilibrium states in a two-dimensional electronic system. Tr-MERTS operates on samples and regimes inaccessible to standard optical pump-probe spectroscopy. First, Tr-MERTS can easily function in the millikelvin temperature range where many correlated electronic phases emerge. In addition, Tr-MERTS permits a precision control of the pumping electron density. Finally, the electrons can be pumped into a specific energy state even for a system with equidistant energy levels, whereas optical methods excite electrons into any available states when a transition energy equals pump photon energy. In this talk, I will discuss the operational principle of Tr-MERTS and describe basic transient features observed in a quantum Hall system.