Spectroscopic Analysis of Vibronic Relaxation Pathways in Molecular Spin Qubit [Ho(W5O18)2]9–: Sparse Spectra Are Key

Blockmon, Avery; Ullah, Aman; Hughey, Kendall D.; Duan, Yan; O’Neal, Kenneth; Ozerov, Mykhaylo; Baldoví, José J.; Aragó, Juan; Gaita‐Ariño, Alejandro; Coronado, Eugenio; Musfeldt, J. L.

doi:10.1021/acs.inorgchem.1c01474

Cited by 25 publications

(32 citation statements)

References 52 publications

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“…The latter are used to define all the coefficients needed to set up the former on a material-specific case and thus enable a nonparametric treatment of all the relevant interactions, such as spin and phonon spectra, and all the spin-phonon coupling coefficients. Applications of this method to magnetic molecules have recently generated large interest, with examples of studies in both molecular qubits (14,17,(20)(21)(22)(23) and single-ion magnets (15,16,(24)(25)(26)(27)(28)(29)(30). Coordination compounds offer a versatile playground to test relaxation theories as their chemical structure and properties can be finely controlled and characterized experimentally (31,32).…”

Section: Introductionmentioning

confidence: 99%

Toward exact predictions of spin-phonon relaxation times: An ab initio implementation of open quantum systems theory

Lunghi

2022

Sci. Adv.

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Spin-phonon coupling is the main driver of spin relaxation and decoherence in solid-state semiconductors at finite temperature. Controlling this interaction is a central problem for many disciplines, ranging from magnetic resonance to quantum technologies. Spin relaxation theories have been developed for almost a century but often use a phenomenological description of phonons and their coupling to spin, resulting in a nonpredictive tool and hindering our detailed understanding of spin dynamics. Here, we combine time-local master equations up to the fourth order with advanced electronic structure methods and perform predictions of spin-phonon relaxation time for a series of solid-state coordination compounds based on both transition metals and lanthanide Kramers ions. The agreement between experiments and simulations demonstrates that an accurate, universal, and fully ab initio implementation of spin relaxation theory is possible, thus paving the way to a systematic study of spin-phonon relaxation in solid-state materials.

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Section: Introductionmentioning

confidence: 99%

Toward exact predictions of spin-phonon relaxation times: An ab initio implementation of open quantum systems theory

Lunghi

2022

Sci. Adv.

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“…In particular, it has been suggested that improved SMM behaviour may be achieved with more rigid systems with fewer low energy phonon modes that afford fast relaxation. [39,40] The magnetic properties of the deuterated compounds 1-Tb D and 1-Dy D were measured for two different particle sizes of the samples, with the observation that for 1-Tb D , particle size influences the slow magnetic relaxation of Raman-like T ~2 relaxation rate, while for 1-Dy D , the slow magnetic relaxation in both the higher temperature Raman regime and lower temperature T 6 phonon-bottleneck regime is unaffected by particle size, as expected for a spectral phonon bottleneck. [34] New solvatomorphs of 1-Ln have also been synthesised, yielding a dichloromethane solvate 2-Ln, and a toluene solvate 3-Ln for Ln = Tb, Dy.…”

Section: Discussionmentioning

confidence: 99%

Magnetic properties and neutron spectroscopy of lanthanoid-{tetrabromocatecholate/18-crown-6} single-molecule magnets

et al. 2022

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Lanthanoid single-molecule magnets (Ln-SMMs) exhibit slow magnetic relaxation at low temperatures. This arises from an energy barrier to magnetisation reversal associated with the crystal field (CF) splitting of the Ln(III) ion. The magnetic relaxation is impacted by the interaction of the molecule with the crystal lattice, so factors including particle size and crystal packing can play an important role. In this work, a family of compounds of general formula [Ln(18-c-6)(NO 3 ) (Br 4 Cat)]•X (Ln = La, Tb, Dy; 18-c-6 = 18-crown-6; Br 4 Cat 2− = tetrabromocatecholate) has been studied by inelastic neutron scattering (INS) and magnetometry to elucidate the effects of crystal packing on the slow magnetic relaxation of the Tb(III) and Dy(III) compounds. The deuterated analogues [Ln(18-c-6-d 24 )(NO 3 )(Br 4 Cat)]•CH 3 CN-d 3 (1-Ln D ; Ln = La, Tb, Dy) have been synthesised, with 1-Tb D and the diamagnetic analogue 1-La D measured by INS. The dynamic magnetic properties of 1-Tb D and 1-Dy D have also been measured and compared for two samples with different particle sizes. To probe packing effects on the slow magnetic relaxation, two new solvatomorphs of the hydrogenous compounds [Ln(18-c-6)(NO 3 )(Br 4 Cat)]•X (2-Ln: X = CH 2 Cl 2 ; 3-Ln: X = 0.5 toluene) have been obtained for Ln = Tb and Dy. The CF splitting between the ground and first excited CF pseudo-doublets has been experimentally determined for 1-Tb D by INS, and strongly rare earth dependent and anharmonic lattice vibrational modes have also been observed in the INS spectra, with implications for slow magnetic relaxation. Dynamic magnetic measurements reveal significant particle-size dependence for the slow magnetic relaxation for 1-Tb D , while a previously reported anomalous phonon bottleneck effect in the 1-Dy D analogue does not change with particle size. Further dynamic magnetic measurements of 2-Ln and 3-Ln show that the slow magnetic relaxation in these Ln-SMMs is strongly dependent on lattice effects and crystal packing, which has implications for the future use of Ln-SMMs in devices.

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“…In these calculations, the evaluation of spin-phonon coupling constants presents the bottleneck of the overall computation. Most commonly, the ground multiplet of electronic states describing the low temperature magnetism is projected onto a phenomenological spin order electronic and vibrational (system and bath) Hamiltonian and spin-phonon (systembath) interaction: Ĥ = ĤS + ĤPh + VS−Ph [10,13,14]. In the case of lanthanide complexes, the phenomenological crystal field Hamiltonian fully describes the splitting and mixing of the ground J-level.…”

Section: Introductionmentioning

confidence: 99%

“…Conventionally, CFP derivatives have been evaluated numerically sampling explicit distortions of the complex along normal mode vectors around its equilibrium structure at the Complete Active Space Self-Consistent Field (CASSCF) level of theory [4,9,10,14].…”

Section: Introductionmentioning

confidence: 99%

An analytic linear vibronic coupling method for first-principles spin-dynamics calculations in single-molecule magnets

Staab

Chilton

2022

Preprint

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The accurate modeling of vibronically driven magnetic relaxation from ab initio calculations is of paramount importance to the design of next generation single-molecule magnets (SMMs). Previous theoretical studies have been relying on numerical differentiation to obtain spin-phonon couplings in the form of derivatives of spin Hamiltonian parameters. In this work, we introduce a novel approach to obtain these derivatives fully analytically by combining the linear vibronic coupling (LVC) approach with analytic CASSCF derivatives and nonadiabatic couplings computed at a single equilibrium geometry and electronic structure. We apply our analytic approach to the computation of Orbach and Raman relaxation rates in a solvated bis-cyclobutadienyl Dy(III) sandwich complex, where the solution environment is modelled by electrostatic multipole expansions, and benchmark our findings against results obtained using conventional numerical derivatives and a fully electronic description of the whole system. Among the ghost, charge and charge+dipole representations, we find that the point charge model shows the best agreement with the reference calculation, but note that the main source of discrepancies observed in the magnetic relaxation rates originates from the approximate equilibrium electronic structure computed using the electrostatic environment models, rather than from the couplings. We demonstrate that our novel LVC approach exhibits high accuracy over a wide range of coupling strengths and enables computational savings due to its analytic, "single-shot'' nature. Evidently, this offers great potential for advancing the simulation of a wide range of vibronic coupling phenomena in magnetism and spectroscopy, ultimately aiding the design of high-performance SMMs.

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Spectroscopic Analysis of Vibronic Relaxation Pathways in Molecular Spin Qubit [Ho(W₅O₁₈)₂]^9–: Sparse Spectra Are Key

Cited by 25 publications

References 52 publications

Toward exact predictions of spin-phonon relaxation times: An ab initio implementation of open quantum systems theory

Toward exact predictions of spin-phonon relaxation times: An ab initio implementation of open quantum systems theory

Magnetic properties and neutron spectroscopy of lanthanoid-{tetrabromocatecholate/18-crown-6} single-molecule magnets

An analytic linear vibronic coupling method for first-principles spin-dynamics calculations in single-molecule magnets

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