Pulsed electron spin resonance spectroscopy in the Purcell regime

Area of Science:

• Quantum physics
• Solid-state physics
• Spectroscopy

Background:

• Electron paramagnetic resonance (EPR) typically relies on spin-lattice and spin-spin interactions for relaxation.
• The Purcell effect, where spins emit photons into a resonator, can become a dominant relaxation pathway under strong spin-resonator coupling and high resonator quality factors.
• Microresonators are increasingly used in EPR to enhance spin-number sensitivity, necessitating an understanding of this novel relaxation regime.

Purpose of the Study:

• To investigate the influence of the Purcell effect on measured EPR signals, specifically spin-echo amplitude and temporal shape.
• To theoretically and experimentally study this regime under varying spin-linewidth and coupling homogeneity conditions.
• To understand how inhomogeneous spin-resonator coupling affects spin-echo relaxation times and signal shape.

Main Methods:

• Theoretical modeling of spin relaxation influenced by resonator coupling.
• Experimental investigation using donor spins in silicon.
• Utilizing saturation recovery sequences for measuring spin-echo relaxation times.
• Analyzing the impact of spin-linewidth relative to resonator bandwidth.

Main Results:

• Inhomogeneous spin-resonator coupling leads to a strong dependence of the effective spin-echo relaxation time on detection echo parameters.
• When spin linewidth exceeds resonator bandwidth, different Fourier components of the spin echo relax at distinct rates.
• The resonator's role in driving relaxation causes the spin-echo temporal shape to become dependent on the experimental repetition time.

Conclusions:

• The Purcell effect significantly alters spin relaxation dynamics in microresonator-enhanced EPR.
• Understanding the interplay between spin properties, resonator characteristics, and coupling homogeneity is crucial for interpreting EPR signals in this regime.
• The findings provide insights into optimizing experimental parameters for accurate measurements and high sensitivity in microresonator-based EPR systems.