Orientation dependence of phase memory relaxation in the V(IV) ion at high frequencies

Tunable Cr4+ Molecular Color Centers

“…This orientation dependence of T m is similar to S = 1/2 systems, where the longest T m times occur for molecules with the principal axes of the g matrix or hyperfine tensor oriented parallel or perpendicular to B 0 . 68,69 These data clearly illustrate that orienting the highest order rotational axis of S > 1/2 molecular spins parallel or perpendicular to an applied external field can help maximize coherence times in the high field limit (i.e., g i μ B B 0 > |D|), assuming that the rotational axis contains the principal axis of the ZFS tensor. 76 However, precisely assigning the dominant orientation-dependent relaxation mechanisms in S = 1 molecular systems will require higher field and frequency pulsed EPR studies to deconvolute the influence of librational and hyperfine-mediated decoherence pathways.…”

“…76 However, precisely assigning the dominant orientation-dependent relaxation mechanisms in S = 1 molecular systems will require higher field and frequency pulsed EPR studies to deconvolute the influence of librational and hyperfine-mediated decoherence pathways. 68,69,77 For the compounds with E ≠ 0, we observe six total local maxima, since x ≠ y in the EDFS spectra 78 S23−S28). We find a similar relationship between molecular orientation and T m .…”

“…Indeed, the Cr 4+ molarities ranged from ∼7 to ∼40 mM (Table S8), which is relatively high compared to pulsed EPR experiments in solution or frozen glassy matrixes. [30][31][32]68,69 Generally, the samples with the lowest concentrations, such as 2′ and 3′, exhibit longer T m times, while more concentrated samples, such as 1′, exhibit T m times nearly 3 times shorter despite similar 1 H environments between 1′, 2′, and 3′. Indeed, increasing the Cr 4+ concentration for 2′ from 7 to 22 mM results in a 4-fold reduction of T m (Figure S7).…”

“…Previous studies with S = 1/2 transition-metal-based systems have demonstrated that coherence times vary as a function of molecular orientation with respect to an external magnetic field (denoted as B 0 ), for example, due to librational motion. 68,69 Alternatively, hyperfine-mediated relaxation mechanisms have dictated the orientation-dependent T 2 times for NV − centers. 70 Further understanding this orientation dependence is critical when designing molecular-vector-based magnetic field sensors analogous to solid state color centers.…”

Deconvolving Contributions to Decoherence in Molecular Electron Spin Qubits: A Dynamic Ligand Field Approach

“…Finally, the V(IV) qubit (n-Bu3NH)2[V(C6H4O2)3] in a frozen glass has demonstrated 20 % variation in TM times as a function of field position, consistent with motional contributions to decoherence. [60] It is to be expected that other V(IV) qubits will demonstrate the same behavior. These examples show how sample preparation and measurement conditions can place a qubit into any one of the three decoherence regimes.…”