High resolution time- and angle-resolved photoemission spectroscopy with 11 eV laser pulses

Abstract

Performing time and angle resolved photoemission spectroscopy (tr-ARPES) at high momenta necessitates extreme ultraviolet laser pulses, which are typically produced via high harmonic generation (HHG). Despite recent advances, HHG-based setups still require large pulse energies (hundreds of µ J to mJ) and their energy resolution is limited to tens of meV. Here, we present a novel 11 eV tr-ARPES setup that generates a flux of 5× 10 10 photons/s and achieves an unprecedented energy resolution of 16 meV. It can be operated at high repetition rates (up to 250 kHz) while using input pulse energies down to 3 µ J. We demonstrate these unique capabilities by simultaneously capturing the energy and momentum

Time-resolved ARPES on cuprates: Tracking the low-energy electrodynamics in the time domain

“…As a final outlook, we remark that although most of the TR-ARPES studies carried out so far on cuprates have relied on near ∼ 6 eV probe systems with near-IR pump excitation, in the coming years we foresee new and fascinating explorations of ultrafast dynamics and light-induced phases of matter. The development of highrepetition rate and high-energy/temporal resolution TR-ARPES systems with high-harmonic XUV probes [57][58][59][60], and pump excitations in the mid-IR/THz range [9,10,66], will surely pave the way towards exciting and unprecedented investigations of out-of-equilibrium properties of quantum materials over the full momentum space. The most exciting times lie ahead!…”

“…As a final consideration to conclude this brief overview of the TR-ARPES investigations of cuprates, one may notice that most of the aforementioned works have been performed using a near-IR pump excitation and lowenergy (∼ 6 eV) probe photons [42], which are intrinsically limited to the study of the near-nodal momentum region. Even though high-harmonics-based TR-ARPES systems have been available for more than a decade, only very recently has the combination of high-stability, highrepetition rate, and sub-50 meV energy resolution been achieved [57][58][59][60], thus paving the way towards fascinating studies of low-energy electrodynamics over the whole Brillouin zone of cuprates, as well as other quantum materials. As for the optical excitation, despite its easy accessibility, the commonly-used ∼ 1.5 eV pump energy bears some critical limitations, as it redistributes carriers around the entire momentum space, without cou-…”

Expanding the momentum field of view in angle-resolved photoemission systems with hemispherical analyzers

“…The application of a bias voltage is not limited to photoemission with 6 eV photons used in this study. In this context we note the recent development of an ultrafast 11 eV laser for time-resolved studies 32,33 and a quasi-continuous wave 11 eV laser for high resolution ARPES. 7,34 Time-resolved ARPES experiments relying on 6 eV probe photon energies particularly benefit from measuring the electron dynamics over a large part of the Brillouin zone in a fixed configuration.…”

A narrow bandwidth extreme ultra-violet light source for time- and angle-resolved photoemission spectroscopy

“…Over the past decades, there have been great improvements in synchrotron-based light sources which, together with new and more versatile electron analyzers, have pushed the energy and momentum-space resolutions in ARPES experiments to ever increasing levels 4,5 . In parallel to this development, ARPES has taken a leap into the time-domain due to the advent of femtosecond high-power lasers that have enabled ultrafast extreme-ultraviolet (XUV) light sources based on high-harmonic generation (HHG) in noble gases [6][7][8][9] or nonlinear crystals [10][11][12] . While several successful implementations of time-and angle-resolved photoemission spectroscopy (tr-ARPES) systems have been demonstrated, the technique continues to rapidly evolve and there is still much progress to be made in terms of increased repetition rate, photon flux, improved time and energy resolutions, photon energy and momentum range coverage as well as pump versatility.…”