Hyperfine Structure and Coherent Dynamics of Rare-Earth Spins Explored with Electron-Nuclear Double Resonance at Subkelvin Temperatures

Abstract

An experimental platform of ultralow-temperature pulsed ENDOR (electron-nuclear double resonance) spectroscopy is constructed for the bulk materials. Coherent property of the coupled electron and nuclear spins of the rare-earth (RE) dopants in a crystal ( 143 Nd 3+ :Y2SiO5) is investigated from 100 mK to 6 K. At the lowest working temperatures, two-pulse-echo coherence time exceeding 2 ms and 40 ms are achieved for the electron and nuclear spins, while the electronic Zeeman and hyperfine population lifetimes are more than 15 s and 10 min. With the aid of the near-unity electron spin polarization at 100 mK, the complete hyperfine level structure with 16 energy levels is measured using ENDOR technique without the assistance of the reconstructed spin Hamiltonian. These results demonstrate the suitability of the deeply cooled paramagnetic RE-doped solids for memory components aimed for quantum communication and quantum computation. The developed experimental platform is expected to be a powerful tool for paramagnetic materials from various research fields.

Twenty-three–millisecond electron spin coherence of erbium ions in a natural-abundance crystal

“…Since the nuclear-spin contribution is temperature independent in the experimental range, we attribute this decrease to spectral diffusion caused by all the other paramagnetic impurities present in similar or larger concentrations than erbium (see section S1.1). This spectral diffusion is quenched at low temperatures when most paramagnetic impurities are highly polarized into their ground state ( 30 , 35 , 36 ). We use the theoretical nuclear spin decoherence curve of Fig.…”

Extending the spin coherence lifetimes of 167Er3+:Y2SiO5 at Sub-Kelvin Temperatures

“…Traditionally, pulsed ENDOR measurements are hard to be applicable for general bulk materials at ultralow temperatures due to the large power dissipation required for nuclear spin manipulations [39]. In our recent work we have achieved this goal by successfully combining the pulsed EPR/ENDOR spectrometer within a dilution refrigerator (Triton 400, Oxford Instruments) [30]. The lowest sample temperature is verified to be less than 100…”

“…Compared with a higher magnetic field, resorting to a lower sample temperature can avoid the problems mentioned above. Moreover, electron spin flips caused by the spin-lattice relaxation (SLR) process will be significantly inhibited due to the reduction in phonon concentration when going to lower temperatures [28,30,31].…”

“…Pulsed EPR (Electron Paramagnetic Resonance Spectroscopy) and ENDOR (Electron Nuclear DOuble Resonance) spectroscopy is the classic methodology to study the coherent dynamics of the coupled electron and nuclear spin systems [32,33]. Compared with optical spectroscopy, it can provide much higher spectral resolution because of the significantly lower inhomogeneous broadening of the spin transitions [30,34]. Coherence can be transferred between the electronic and nuclear spins with high fidelity [35].…”

“…Coherence can be transferred between the electronic and nuclear spins with high fidelity [35]. There have been some previous reports on pulsed-EPR measurements of rare-earth-ion-doped materials at sub-Kelvin temperatures [13,36], while pulsed ENDOR spectroscopy at sub-Kelvin temperatures has only been implemented for 143 Nd 3+ :Y 2 SiO 5 recently [30]. Here, we implement the first pulsed ENDOR investigation for an Er 3+ doped material at sub-Kelvin temperatures.…”