Chapter 5
Analysis
The experiment we conduct is based on the premise that monopoles traversing the
pickup coil of a SQUID will thread flux ∗ through it, proportional to their charge
±m ∗ . Instead of step function jumps in the SQUID signal (Fig. 2.7), a magnetic
noise (t) (Fig. 2.8) is expected to be detected by the highly sensitive flux noise
spectrometer developed for this experiment. This noise originates from a thermally
stimulated dense plasma of monopoles that get generated and may recombine in
the temperature range 1.2K ≤ T ≤ 4K. In this chapter, the experimental results
of Spin Noise Spectroscopy of Dysprosium Titanate are presented and analyzed.
These results are then compared to the predictions made by the analytic formulation
of generation recombination noise as well as Monte Carlo simulations of spin noise
coming from a Dy 2 Ti 2 O 7 sample.
Our measurements of this magnetic noise S (ω, T ) have revealed a strong
temperature and frequency dependence. We discover that the noise has a distinct
shape—a plateau at low frequencies (ωτ 1) and an eventual decay at higher
frequencies (ωτ 1). The inflection point for this noise (ωτ ≈ 1) can reveal
details about the microscopic time constant in the monopole motion through the
material. We find that the temperature dependence of the detected S (ω, T ) is
counter-intuitive.
5.1 Analytic Structure of Noise
Flux noise from a sample of Dy 2 Ti 2 O 7 , which is theoretically presumed to host
a plasma of magnetic monopoles, is measured via spin noise spectroscopy. To
check if noise originating from generation and eventual recombination of magnetic
monopoles as outlined in the previous chapter best explains the structure of our
© Springer Nature Switzerland AG 2021
R. Dusad, Magnetic Monopole Noise, Springer Theses,
https://doi.org/10.1007/978-3-030-58193-0_5
43
Analysis
The experiment we conduct is based on the premise that monopoles traversing the
pickup coil of a SQUID will thread flux ∗ through it, proportional to their charge
±m ∗ . Instead of step function jumps in the SQUID signal (Fig. 2.7), a magnetic
noise (t) (Fig. 2.8) is expected to be detected by the highly sensitive flux noise
spectrometer developed for this experiment. This noise originates from a thermally
stimulated dense plasma of monopoles that get generated and may recombine in
the temperature range 1.2K ≤ T ≤ 4K. In this chapter, the experimental results
of Spin Noise Spectroscopy of Dysprosium Titanate are presented and analyzed.
These results are then compared to the predictions made by the analytic formulation
of generation recombination noise as well as Monte Carlo simulations of spin noise
coming from a Dy 2 Ti 2 O 7 sample.
Our measurements of this magnetic noise S (ω, T ) have revealed a strong
temperature and frequency dependence. We discover that the noise has a distinct
shape—a plateau at low frequencies (ωτ 1) and an eventual decay at higher
frequencies (ωτ 1). The inflection point for this noise (ωτ ≈ 1) can reveal
details about the microscopic time constant in the monopole motion through the
material. We find that the temperature dependence of the detected S (ω, T ) is
counter-intuitive.
5.1 Analytic Structure of Noise
Flux noise from a sample of Dy 2 Ti 2 O 7 , which is theoretically presumed to host
a plasma of magnetic monopoles, is measured via spin noise spectroscopy. To
check if noise originating from generation and eventual recombination of magnetic
monopoles as outlined in the previous chapter best explains the structure of our
© Springer Nature Switzerland AG 2021
R. Dusad, Magnetic Monopole Noise, Springer Theses,
https://doi.org/10.1007/978-3-030-58193-0_5
43