Dark matter electron interactions in detector materials
Doctoral thesis, 2024
Dark Matter (DM) makes up 85% of the matter content of the universe, and
its gravitational effects are seen on scales ranging from that of cosmology to
that of galactic astrophysics. The nature of DM is, however, unknown. Study-
ing DM in the lab with a class of experiments called direct detection (DD)
experiments is key to understanding its properties. For decades, experiments
have been attempting to do this through searches for DM induced nuclear
recoils. These have not been found, and a possible reason for this is that the
hypothetical DM particle is too light to induce nuclear recoils. Therefore, in
the last decade experiments have been built to study DM through electron
recoils instead. As the electron is 4 orders of magnitude lighter than the nu-
cleus, electron recoils can be induced by DM down to 4 orders of magnitude
lighter than the lightest DM particle probeable with nuclear recoils.
In order to understand current and upcoming results from experiments
searching for DM induced electron recoils, a theoretical understanding of DM
electron scatterings in detector materials is needed. When modelling such
electron interactions, one need input both from DM and material physics.
This thesis improves the theoretical understanding by both improving the
material description using density functional theory (DFT), and by extending
the DM description using non-relativistic effective theory (NR-EFT) tools.
The improvement gives not only a more accurate description of the DM-
electron interactions that the experiments are expected to see; it also vastly
extends the forms of DM that can be studied in direct detection experiments.
Before this extension, one typically focused on a benchmark case of DM, the
so called dark photon model. With this extension, one can cover all forms of
gravitationally bound DM with spins of 0, 1/2 or 1.
In the included works, advances are made in the description of DM-electron
interactions in common detector materials such as liquid xenon, silicon and
germanium, as well as to materials in the research and development phase,
such as graphene and carbon nanotubes (CNTs).
its gravitational effects are seen on scales ranging from that of cosmology to
that of galactic astrophysics. The nature of DM is, however, unknown. Study-
ing DM in the lab with a class of experiments called direct detection (DD)
experiments is key to understanding its properties. For decades, experiments
have been attempting to do this through searches for DM induced nuclear
recoils. These have not been found, and a possible reason for this is that the
hypothetical DM particle is too light to induce nuclear recoils. Therefore, in
the last decade experiments have been built to study DM through electron
recoils instead. As the electron is 4 orders of magnitude lighter than the nu-
cleus, electron recoils can be induced by DM down to 4 orders of magnitude
lighter than the lightest DM particle probeable with nuclear recoils.
In order to understand current and upcoming results from experiments
searching for DM induced electron recoils, a theoretical understanding of DM
electron scatterings in detector materials is needed. When modelling such
electron interactions, one need input both from DM and material physics.
This thesis improves the theoretical understanding by both improving the
material description using density functional theory (DFT), and by extending
the DM description using non-relativistic effective theory (NR-EFT) tools.
The improvement gives not only a more accurate description of the DM-
electron interactions that the experiments are expected to see; it also vastly
extends the forms of DM that can be studied in direct detection experiments.
Before this extension, one typically focused on a benchmark case of DM, the
so called dark photon model. With this extension, one can cover all forms of
gravitationally bound DM with spins of 0, 1/2 or 1.
In the included works, advances are made in the description of DM-electron
interactions in common detector materials such as liquid xenon, silicon and
germanium, as well as to materials in the research and development phase,
such as graphene and carbon nanotubes (CNTs).
effective theory
Dark matter
direct detection
PJ-salen
Opponent: Prof. David Cerdeño, Universidad Autónoma de Madrid, Spain
Author
Einar Urdshals
Chalmers, Physics, Subatomic, High Energy and Plasma Physics
Crystal responses to general dark matter-electron interactions
Physical Review Research,;Vol. 3(2021)
Journal article
Dark matter-electron interactions in materials beyond the dark photon model
Journal of Cosmology and Astroparticle Physics,;Vol. 2023(2023)
Journal article
Direct searches for general dark matter-electron interactions with graphene detectors: Part I. Electronic structure calculations
Physical Review Research,;Vol. 5(2023)
Journal article
Direct searches for general dark matter-electron interactions with graphene detectors: Part II. Sensitivity studies
Physical Review Research,;Vol. 5(2023)
Journal article
R. Catena, L. Marin, M. Matas, N. A. Spaldin, and E. Urdshals. "Density functional theory description of xenon for light dark matter direct detection"
R. Catena and E. Urdshals. Dark Matter-induced electron excitations in silicon and germanium with Deep Learning
All that you touch, and all that you see, is made of light and atoms. The light and atoms do, however, only make up around 5% of the universe. The rest of the universe consists of dark energy and dark matter. The latter is known to be responsible for formation and holding together of galaxies, but little else is known of its nature. Uncovering more of the nature of dark matter is a key task for modern physics.
One of the ways in which we look for the nature of dark matter is by searching for rare interactions between dark matter particles and ordinary matter, hoping to study these interactions in the lab. When doing these searches, we need to know what we are looking for. We need to know what it looks like when a dark matter particle interacts with ordinary matter. This is where my thesis contributes.
In my thesis, I model the interaction between dark matter particles and electrons in materials. I do this for several different materials used to search for dark matter, such as silicon and germanium crystals, graphene, carbon nanotubes and liquid xenon. I push the frontier both by improving upon the existing modelling of dark matter electron interactions in these materials, and by modelling kinds of dark matter particles that have not previously been considered. The approach used in this thesis allows for covering a wide range of possible dark matter electron interactions at the same time, making clear the diversity in possible dark matter electron interactions.
One of the ways in which we look for the nature of dark matter is by searching for rare interactions between dark matter particles and ordinary matter, hoping to study these interactions in the lab. When doing these searches, we need to know what we are looking for. We need to know what it looks like when a dark matter particle interacts with ordinary matter. This is where my thesis contributes.
In my thesis, I model the interaction between dark matter particles and electrons in materials. I do this for several different materials used to search for dark matter, such as silicon and germanium crystals, graphene, carbon nanotubes and liquid xenon. I push the frontier both by improving upon the existing modelling of dark matter electron interactions in these materials, and by modelling kinds of dark matter particles that have not previously been considered. The approach used in this thesis allows for covering a wide range of possible dark matter electron interactions at the same time, making clear the diversity in possible dark matter electron interactions.
Dark Matter electron scattering in detector materials
Stiftelsen Wilhelm och Martina Lundgrens Vetenskapsfond (2021-3861), 2021-06-01 -- 2022-12-31.
Empirical Determination of the Dark Matter Particle Spin
Swedish Research Council (VR) (2018-05029), 2019-01-01 -- 2022-12-31.
Subject Categories
Subatomic Physics
Astronomy, Astrophysics and Cosmology
Condensed Matter Physics
Roots
Basic sciences
Infrastructure
C3SE (Chalmers Centre for Computational Science and Engineering)
ISBN
978-91-8103-031-0
Doktorsavhandlingar vid Chalmers tekniska högskola. Ny serie: 5489
Publisher
Chalmers
PJ-salen
Opponent: Prof. David Cerdeño, Universidad Autónoma de Madrid, Spain