Abstract
AbstractThe readout in the dispersive regime is originally developed—and it is now largely exploited—for non‐demolitive measurement of super‐ and semiconducting qubits. More recently it has been successfully applied to probe collective spin excitations in ferro(i)magnetic bulk samples or collections of paramagnetic spin centers embedded into microwave cavities. The use of this readout technique within a semiclassical limit of excitation is only marginally investigated although it holds for a wide class of problems, including advanced magnetic resonance techniques. In this work, the coupling between a coplanar microwave resonator and diphenyl‐nitroxide organic radical diluted in a fully deuterated benzophenone single crystal is investigated. Two‐tone transmission spectroscopy experiments demonstrate the possibility to reconstruct the spectrum of the spin system with little loss of sensitivity with respect to the resonant regime. Likewise, pulse sequences of detuned microwave frequency allow the measurement of the spin‐lattice relaxation time (T1). The independent tunability of the probe and the drive power enables one to adjust the signal‐to‐noise ratio of the spectroscopy. These results suggest that electron spin dispersive spectroscopy can be used as a complementary tool of electron spin resonance to investigate the spin response.
Highlights
The readout in the dispersive regime is originally developed—and it is spectroscopy
We report an extensive investigation on the dispersive regime achieved between a 1.5% diluted crystal of DPNO molecular spin ensemble and a superconducting coplanar microwave resonator at low temperature (2 K)
We investigated the transmission spectroscopy in the dispersive limit of the coupling between a DPNO organic radical diluted in its nonmagnetic host crystal and a coplanar microwave resonator at low temperature
Summary
We consider the interaction of an ensemble of N spins s coupled to a photon mode (resonant frequency ν0) within the Tavis– Cummings model, whose Hamiltonian reads as[22,45,46,47,48]:. According to the Bloch equations, the response of the spins is expected to be proportional to the applied MW magnetic field, as for the quantum regime.[56,60] This suggests that in the weakly coupled dispersive limit (defined by Δ ≫ Ω), effects on the energy of the resonator are expected. This situation corresponds to a transmission spectroscopy of the spin ensemble which, differently from ESR spectroscopy, 2100039 (3 of 12). A similar measurement at 0 T gives no shifts, confirming that this effect is given by the interaction with the spins
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