Low-temperature magnetic studies of two isotopologues dimers, with and without nuclear spins, reveal that, at very low temperatures, the nuclear spin facilitates the coupling to the phonon bath enhancing the direct relaxation process; observation reflected in the temperature and field dependence of the relaxation rates, whilst at higher temperatures the effect of the nuclear spins is less relevant.
As an extension of two-level quantum bits (qubits), multilevel systems, so-called qu dits, where d represents the Hilbert space dimension, have been predicted to reduce the number of iterations in quantum-computation algorithms. This has been tested in the well-known [TbPc] single-molecule magnet (SMM), which allowed implementation of the Grover algorithm in a single molecular unit. In the quest for molecular systems possessing an increased number of accessible nuclear spin states, we explore herein a dimeric Tb-SMM via single-crystal μ-SQUID measurements at sub-Kelvin temperatures. We observe ferromagnetic interactions between the Tb ions and cooperative quantum tunneling of the electronic spins with spin ground state | J = ±6⟩. Strong hyperfine coupling with the Tb nuclear spins leads to a multitude of spin-reversal paths, leading to seven strong hyperfine-driven tunneling steps in the hysteresis loops. Our results show the possibility of reading out the Tb nuclear spin states via cooperative tunneling of the electronic spins, making the dimeric Tb-SMM an excellent nuclear spin qu dit candidate with d = 16.
Quantum tunneling dominates the low temperature magnetization dynamics in molecular magnets and presents features that are strongly system dependent. The current discussion is focused on the terbium(III) bis(phtalocyanine) ([TbPc2]−1) complex that should serve as a prototypical case for lanthanide molecular magnets. We analyze numerically the effect of non-axial interactions on the magnitude of the intrinsic tunnel splitting and show that usual suspects like the transverse ligand field and Zeeman interaction fail to explain the experimentally observed dynamics. We then propose through the nuclear quadrupolar interaction a viable mechanism that mixes, otherwise almost degenerate hyperfine states.
Results on dynamical fluctuations of charged particles in the pseudorapidity space of central C-Cu interactions at 4.5 A GeV/c are performed in the transformed variables and using higher order scaled factorial moments modifyied to remove the bias of infinite statistics in the normalization. The intermittency behavior is found up to eighth order of the moments increasing with the order and leading to the pronounced multifractality. Two differed intermittent-like rises are obtained, one indicating an occurrence of the non-thermal phase transition, and no critical behavior is found to be reached in another case. The observations may be treated to show different regimes of particle production during the cascade. Comparison with some conventional model approximations notes the multiparticle character of the fluctuations. The results presented can be effective in sense of sensitivity of intermittency to the hadronization phase.
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