We report on terahertz (THz) electron paramagnetic resonance generalized spectroscopic ellipsometry (THz-EPR-GSE). Measurements of field and frequency dependencies of magnetic response due to spin transitions associated with nitrogen defects in 4H-SiC are shown as an example. THz-EPR-GSE dispenses with the need of a cavity, permits independently scanning field and frequency parameters, and does not require field or frequency modulation. We investigate spin transitions of hexagonal ( h) and cubic ( k) coordinated nitrogen including coupling with its nuclear spin (I = 1), and we propose a model approach for the magnetic susceptibility to account for the spin transitions. From the THz-EPR-GSE measurements, we can fully determine polarization properties of the spin transitions, and we can obtain the k coordinated nitrogen g and hyperfine splitting parameters using magnetic field and frequency dependent Lorentzian oscillator line shape functions. Magnetic-field line broadening presently obscures access to h parameters. We show that measurements of THz-EPR-GSE at positive and negative fields differ fundamentally and hence provide additional information. We propose frequency-scanning THz-EPR-GSE as a versatile method to study properties of spins in solid state materials.
This content will become publicly available on March 1, 2025
Universal determination of comagnetometer response to spin couplings
We propose and demonstrate a general method to calibrate the frequency-dependent response of selfcompensating
noble-gas–alkali-metal comagnetometers to arbitrary spin perturbations. This includes magnetic
and nonmagnetic perturbations such as rotations and exotic spin interactions. The method is based on a fit of
the magnetic field response to an analytical model. The frequency-dependent response of the comagnetometer
to arbitrary spin perturbations can be inferred using the fit parameters. We demonstrate the effectiveness of this
method by comparing the inferred rotation response to an experimental measurement of the rotation response.
Our results show that experiments relying on zero-frequency calibration of the comagnetometer response can
over- or underestimate the comagnetometer sensitivity by orders of magnitude over a wide frequency range.
Moreover, this discrepancy accumulates over time as operational parameters tend to drift during comagnetometer
operation. The demonstrated calibration protocol enables accurate prediction and control of comagnetometer
sensitivity to, for example, ultralight bosonic dark-matter fields coupling to electron or nuclear spins, as well as
accurate monitoring and control of the relevant system parameters.
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- Award ID(s):
- 2110388
- PAR ID:
- 10533768
- Publisher / Repository:
- American Physical Society
- Date Published:
- Journal Name:
- Physical Review Research
- Volume:
- 6
- Issue:
- 1
- ISSN:
- 2643-1564
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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