Detection of sub-MeV Dark Matter with Three-Dimensional Dirac Materials (1708.08929v2)

Abstract: We propose the use of three-dimensional Dirac materials as targets for direct detection of sub-MeV dark matter. Dirac materials are characterized by a linear dispersion for low-energy electronic excitations, with a small band gap of O(meV) if lattice symmetries are broken. Dark matter at the keV scale carrying kinetic energy as small as a few meV can scatter and excite an electron across the gap. Alternatively, bosonic dark matter as light as a few meV can be absorbed by the electrons in the target. We develop the formalism for dark matter scattering and absorption in Dirac materials and calculate the experimental reach of these target materials. We find that Dirac materials can play a crucial role in detecting dark matter in the keV to MeV mass range that scatters with electrons via a kinetically mixed dark photon, as the dark photon does not develop an in-medium effective mass. The same target materials provide excellent sensitivity to absorption of light bosonic dark matter in the meV to hundreds of meV mass range, superior to all other existing proposals when the dark matter is a kinetically mixed dark photon.

Detection of Sub-MeV Dark Matter via Dirac Materials

In recent developments at the intersection of condensed matter physics and dark matter research, Dirac materials have emerged as promising candidates for detecting sub-MeV dark matter (DM). This paper explores the utilization of three-dimensional (3D) Dirac materials for the direct detection of DM, specifically focusing on the interactions with kinetically mixed dark photons, which are considered potential mediators in DM-electron interactions.

Overview

The paper proposes that Dirac materials, characterized by a linear electronic dispersion relation, can serve as effective targets for DM, both through electron scattering and DM absorption processes. The materials possess a small band gap, which can be particularly responsive to low-energy dark matter particles. The work details the formalism developed for calculating scattering and absorption events in Dirac materials, highlighting the momentum transfer dynamics and in-medium effects that distinguish these targets from other classes like superconductors and traditional semiconductors.

Numerical Findings

A key claim is the strong sensitivity of Dirac materials to dark photon absorption, rivaling and surpassing existing detection proposals, especially when considering electrons coupling via light kinetically mixed dark photons. The paper includes rigorous computational analyses, such as density functional theory (DFT) applied to potential target materials like ZrTe₅. The computation reveals optimal detection properties under selected parameters, such as Fermi velocities and band gaps within these materials.

Implications

Practically, the research opens avenues for deploying Dirac materials in experimental setups aiming to detect DM in the keV to MeV mass range, providing alternative modalities alongside superconducting targets. Theoretically, the Ward identity's role in maintaining massless photon interactions within Dirac materials suggests potential advantages in probing extremely light DM scenarios that would be otherwise concealed in other mediums due to in-medium mass effects.

Future Prospects

The paper anticipates improvements in sensitivity through the synthesis of better Dirac material candidates, with attention to maximizing electron sensitivity while controlling thermal noise. An intriguing aspect relates to the directional detection potential presented by the anisotropic band structures of some Dirac materials, which might offer detailed insights into the velocity distribution of DM particles beyond standard isotropic assumptions.

In conclusion, Dirac materials stand to deliver enhanced detection capabilities for sub-MeV dark matter, marking a promising direction in the hunt for hidden sectors in DM research. Their unique physical properties underscore the importance of multidimensional approaches in advancing both theoretical understanding and experimental techniques in dark matter detection.