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Register a new userA Proposal to Detect Dark Matter Using Axionic Topological Antiferromagnets
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Antiferromagnetically doped topological insulators (A-TI) are among the candidates to host dynamical axion fields and axion-polaritons; weakly interacting quasiparticles that are analogous to the dark axion, a long sought after candidate dark matter particle. Here we demonstrate that using the axion quasiparticle antiferromagnetic resonance in A-TIs in conjunction with low-noise methods of detecting THz photons presents a viable route to detect axion dark matter with mass 0.7 to 3.5 meV, a range currently inaccessible to other dark matter detection experiments and proposals. The benefits of this method at high frequency are the tunability of the resonance with applied magnetic field, and the use of A-TI samples with volumes much larger than 1 mm$^3$.
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The axion, originated from the Peccei-Quinn mechanism proposed to solve the strong-CP problem, is a well motivated and popular dark matter candidate. Experimental searches for this hypothetical particle are starting to reach theoretically interesting sensitivity levels. However, only a small fraction of the allowed parameter space has been explored so far, mostly in the $mu$eV (GHz) region, relying on large volume solenoid magnetic fields and microwave resonators with signals read out by quantum noise limited amplifiers. There have been intensive experimental efforts to widen the search range by devising various techniques as well as to enhance sensitivities by implementing advanced technologies. The developments and improvements in these orthogonal approaches will enable us to explore most of the parameter space of the axion and axion-like particles within the next five to ten years. We review the experimental aspects of axion physics and discuss the past, present and future of the individual search programs.
Axion is a popular candidate for dark matter particles. Axionic dark matter may form Bose-Einstein condensate and may be gravitationally bound to form axion clumps. Under the presence of electromagnetic waves with frequency $omega=m_{a}/2$, where $m_{a}$ is the axion mass, a resonant enhancement may occur, causing an instability of the axion clumps. With analytical and numerical approaches, we study the resonant instability of axionic dark matter clumps with infinite homogeneous mass distribution, as well as distribution with a finite boundary. After taking realistic astrophysical environments into consideration, including gravitational redshift and plasma effects, we obtain an instability region in the axion density-clump size parameter space with given mass and coupling of axions. In particular, we show that, for axion clumps formed by the QCD axions in equilibrium, no resonant instability will occur.
A network of synchronized detectors can increase the likelihood of discovering the QCD axion, within the Axion Quark Nugget (AQN) dark matter model. A similar network can also discriminate the X-rays emitted by the AQNs from the background signal. These networks can provide information on the directionality of the dark matter flux (if any), as well as its velocity distribution, and can therefore test the Standard Halo Model. We show that the optimal configuration to detect AQN-induced axions is a triangular network of stations 100 km apart. For X-rays, the optimal network is an array of tetrahedral units.
We study large $N$ 2+1 dimensional fermions in the fundamental representation of an $SU(N)_k$ Chern Simons gauge group in the presence of a uniform background magnetic field for the $U(1)$ global symmetry of this theory. The magnetic field modifies the Schwinger Dyson equation for the propagator in an interesting way; the product between the self energy and the Greens function is replaced by a Moyal star product. Employing a basis of functions previously used in the study of non-commutative solitons, we are able to exactly solve the Schwinger Dyson equation and so determine the fermion propagator. The propagator has a series of poles (and no other singularities) whose locations yield a spectrum of single particle energies at arbitrary t Hooft coupling and chemical potential. The usual free fermion Landau levels spectrum is shifted and broadened out; we compute the shifts and widths of these levels at arbitrary tHooft coupling. As a check on our results we independently solve for the propagators of the conjecturally dual theory of Chern Simons gauged large $N$ fundamental Wilson Fisher bosons also in a background magnetic field but this time only at zero chemical potential. The spectrum of single particle states of the bosonic theory precisely agrees with those of the fermionic theory under Bose-Fermi duality.
Cold dark matter in the Milky Way halo may have structure defined by flows with low velocity dispersion. The Axion Dark Matter eXperiment high resolution channel is especially sensitive to axions in such low velocity dispersion flows. Results from a combined power spectra analysis of the high resolution channel axion search are presented along with a discussion of the assumptions underlying such an analysis. We exclude KSVZ axion dark matter densities of {rho} > 0.2 GeV/cm^3 and DFSZ densities of {rho} > 1.4 GeV/cm^3 over a mass range of m_a = 3.3{mu}eV to 3.69{mu}eV for models having velocity dispersions of {Delta}{beta} < 3x10^-6.
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