54 research outputs found
Probing the Low-Energy Electronic Structure of Complex Systems by ARPES
Angle-resolved photoemission spectroscopy (ARPES) is one of the most direct
methods of studying the electronic structure of solids. By measuring the
kinetic energy and angular distribution of the electrons photoemitted from a
sample illuminated with sufficiently high-energy radiation, one can gain
information on both the energy and momentum of the electrons propagating inside
a material. This is of vital importance in elucidating the connection between
electronic, magnetic, and chemical structure of solids, in particular for those
complex systems which cannot be appropriately described within the
independent-particle picture. The last decade witnessed significant progress in
this technique and its applications, thus ushering in a new era in
photoelectron spectroscopy; today, ARPES experiments with 2 meV energy
resolution and 0.2 degree angular resolution are a reality even for
photoemission on solids. In this paper we will review the fundamentals of the
technique and present some illustrative experimental results; we will show how
ARPES can probe the momentum-dependent electronic structure of solids providing
detailed information on band dispersion and Fermi surface, as well as on the
strength and nature of those many-body correlations which may profoundly affect
the one-electron excitation spectrum and, in turn, determine the macroscopic
physical properties.Comment: Lecture notes for the 2003 Exciting Summer School
(http://www.fysik4.fysik.uu.se/~thor/school.html). A HIGH-RESOLUTION pdf file
is available at http://www.physics.ubc.ca/~damascel/ARPES_Intro.pdf, and
related viewgraphs at http://www.physics.ubc.ca/~damascel/Exciting2003.pd
Optical spectroscopy of quantum spin systems
This thesis work illustrates the results obtained on a number of solid crystalline materials using optical spectroscopy. This experimental technique consists of shing light of different frequencies onto the sample under investigation, and of observing which frequencies are absorbed by the material itself. The experiments were performed in the frequency range extending from the far infrared to the ultra violet (i.e., from 4 meV to 4 eV). ...
Zie: Summary
Time- and Angle-Resolved Photoemission Studies of Quantum Materials
Angle-resolved photoemission spectroscopy (ARPES) -- with its exceptional
sensitivity to both the binding energy and momentum of valence electrons in
solids -- provides unparalleled insights into the electronic structure of
quantum materials. Over the last two decades, the advent of femtosecond lasers,
which can deliver ultrashort and coherent light pulses, has ushered the ARPES
technique into the time domain. Now, time-resolved ARPES (TR-ARPES) can probe
ultrafast electron dynamics and the out-of-equilibrium electronic structure,
providing a wealth of information otherwise unattainable in conventional ARPES
experiments. This paper begins with an introduction to the theoretical
underpinnings of TR-ARPES followed by a description of recent advances in
state-of-the-art ultrafast sources and optical excitation schemes. It then
reviews paradigmatic phenomena investigated by TR-ARPES thus far, such as
out-of-equilibrium electronic states and their spin dynamics, Floquet-Volkov
states, photoinduced phase transitions, electron-phonon coupling, and surface
photovoltage effects. Each section highlights TR-ARPES data from diverse
classes of quantum materials, including semiconductors, charge-ordered systems,
topological materials, excitonic insulators, van der Waals materials, and
unconventional superconductors. These examples demonstrate how TR-ARPES has
played a critical role in unraveling the complex dynamical properties of
quantum materials. The conclusion outlines possible future directions and
opportunities for this powerful technique.Comment: To appear in Reviews of Modern Physic
Tracking local magnetic dynamics via high-energy charge excitations in a relativistic Mott insulator
We use time- and energy-resolved optical spectroscopy to investigate the
coupling of electron-hole excitations to the magnetic environment in the
relativistic Mott insulator NaIrO. We show that, on the picosecond
timescale, the photoinjected electron-hole pairs delocalize on the hexagons of
the Ir lattice via the formation of quasi-molecular orbital (QMO) excitations
and the exchange of energy with the short-range-ordered zig-zag magnetic
background. The possibility of mapping the magnetic dynamics, which is
characterized by typical frequencies in the THz range, onto high-energy (1-2
eV) charge excitations provides a new platform to investigate, and possibly
control, the dynamics of magnetic interactions in correlated materials with
strong spin-orbit coupling, even in the presence of complex magnetic phases.Comment: 5 pages, 4 figures, supplementary informatio
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