Ultrafast time- and angle-resolved photoemission spectroscopy with widely tunable probe photon energy of 5.3–7.0 eV for investigating dynamics of three-dimensional materials

Abstract

Time- and angle-resolved photoemission spectroscopy (TrARPES) is a powerful technique for capturing the ultrafast dynamics of charge carriers and revealing photo-induced phase transitions in quantum materials. However, the lack of widely tunable probe photon energy, which is critical for accessing the dispersions at different out-of-plane momentum kz in TrARPES measurements, has hindered the ultrafast dynamics investigation of 3D quantum materials, such as Dirac or Weyl semimetals. Here, we report the development of a TrARPES system with a highly tunable probe photon energy from 5.3 to 7.0 eV. The tunable probe photon energy is generated by the fourth harmonic generation of a tunable wavelength femtosecond laser source by combining a β-BaB2O4 crystal and a KBe2BO3F2 crystal. A high energy resolution of 29–48 meV and time resolution of 280–320 fs are demonstrated on 3D topological materials ZrTe5 and Sb2Te3. Our work opens up new opportunities for exploring ultrafast dynamics in 3D quantum materials.

Population Inversion and Dirac Fermion Cooling in 3D Dirac Semimetal Cd3As2

“…In TrARPES, the maximum photon energy generated from the fourth harmonic generation (FHG) of the BBO crystal is 6.3 eV, , which is not sufficient to access the Dirac node yet. The KBBF crystal can extend the FHG output to 7.0 eV, and a continuously tunable photon source covering 5.6–7.0 eV has been used in static laser-based ARPES measurements. , Here we develop its time-resolved version to facilitate ultrafast dynamic studies of 3D materials as shown in Figure d (see more details in ref ). A laser beam with a tunable wavelength of 710–930 nm and a pulse duration of 50–80 fs is generated from a Ti:sapphire oscillator and split into pump and probe beams.…”

High-resolution time- and angle-resolved photoemission studies on quantum materials

“…A combination of two β-BaB 2 O 4 (BBO) crystals is used to generate probe pulses with a wavelength at 205 nm to realize high time and energy resolution, and an optional combination of a BBO and a KBe 2 BO 3 F 2 (KBBF) crystal is used to generate probe pulses with a wavelength longer than 185 nm in air to reach higher probe photon energy. In a recent study, the KBBF crystal is used to extend the wavelength of the probe laser pulse to 177 nm in the vacuum chamber [51].…”

Multispectral time-resolved energy-momentum microscopy using high-harmonic extreme ultraviolet radiation

“…Thus, our tomographic data cover ≈39% of the BZ volume. For crystalline materials with smaller k z dimensions, particularly layered 3D electron materials, 9,10,17,34 larger portions of the bulk BZ or entire bulk BZs can be scanned. Similarly, for layers of 3D molecules, 62 3D orbital momentum tomograms can be recorded.…”

“…Over the past fifteen years, trARPES has evolved into a powerful ARPES modality providing direct dynamical information on electronic structure at the fundamental time scales of electronic and atomic motion, particularly on photoinduced transient changes of electronic states and their population. [23][24][25][26][27][28][29][30][31][32] trARPES is now routinely performed using table-top laser sources based on fourth and higher harmonic generation (HHG) in solids 33,34 and gases [35][36][37][38][39][40][41][42][43][44][45][46][47][48][49][50] , respectively, as well as using free-electron lasers (FELs) based on the self-amplification of spontaneous emission (SASE) of free electrons in undulators. 21 The corresponding probe photon energies in trARPES range from the far UV to soft x-rays where a sweet spot currently is the intermediate extreme ultraviolet (XUV) regime.…”