Time-resolved ARPES systems in NSRRC

Hao-Hsiang Jia^3,1, Tien-Tien Yeh^1,2, Sheng-Chiao Wang^2,1, Cheng-Maw Cheng¹, Chih-Wei Luo², Ming-Chang Chen³, Ping-Hui Lin^1*

¹National Synchrotron Radiation Research Center, HsinChu, Taiwan
²Department of Electrophysics, National Yang Ming Chiao Tung University, HsinChu, Taiwan
³Institute of Photonics Technologies, National Tsing Hua University, HsinChu, Taiwan

* Presenter:Ping-Hui Lin, email:phlinjoy@gmail.com

Tr-ARPES provides a direct insight into the electron dynamics with temporal, energy, and momentum-resolved information in one experiment. For novel experiments, such as e.g. strongly correlated electron systems, superconductors, topological insulators, and transition metal dichalcogenides, various entangled collective excitations contribute to the emergence of widespread and multifarious intriguing physical properties. The relaxation of the photon-excited hot electrons would redistribute the energy via a sequence of inter- or intra-band scattering, and thus, the system goes back to equilibrium. ARPES reveals detailed band dispersion with momentum and energy resolution. Furthermore, the pump-probe scheme introduces the temporal resolution via ultra-short pulses, allowing us to disentangle series of continuous events that take place at different point-in-time. Additionally, since the pump pulse brought the electrons up to the unoccupied state, Tr-ARPES makes it possible to peek into the band structure above the Fermi level.
Intriguing research works have been performed on various novel material systems recently using Tr-ARPES technique. For instance, the searching of bright/dark excitons in 2D materials [1,2], the tracking of hot carriers in the topological family or graphene/graphite[3, 4], or the ultrafast relaxation behaviors of collective excitations [5,6]. On top of that, in some cases, the pump pulse is no longer simply playing a role as a weak perturbation, but a driving force of a series of photon-induced quantum states [7,8]. All the aforementioned fascinating physics happens in the exciting transient dynamic field. No doubt, Tr-ARPES will be one of the most powerful tools for studying such phenomena, as it provides energy-, momentum- and temporal-resolved information.

Keywords: Tr-ARPES, pump and probe, many body effects