Entanglement of Exchange-Coupled Dimers of Single-Molecule Magnets

Abstract

Recent EPR studies of a family of [Mn 4 O 3 Cl 4 (O 2 CR) 3 (py) 3 ] 2 (R = CH 3 , CH 2 CH 3 , etc.) dimers of singlemolecule magnets (SMMs) have demonstrated quantum entanglement between the two SMMs within the dimer. This entanglement is caused by an intra-dimer exchange interaction JŜ 1 •Ŝ 2 , where J ≈ +0.1 K and S 1 = S 2 = 9/2. We compare data for two members of the [Mn 4 O 3 Cl 4 (O 2 CR) 3 (py) 3 ] 2 family, focusing on factors which directly affect the coherence of the tunnel-split superposition states.

Supramolecular aggregates of single-molecule magnets: exchange-biased quantum tunneling of magnetization in a rectangular [Mn3]4 tetramer

“…SMMs have also been shown to display interesting quantum phenomena such as quantum tunneling of magnetization (QTM), 11 , 12 quantum phase interference (QPI), 13 , 14 , 15 spin–spin cross relaxation, 16 and quantum entanglement. 17 , 18 , 19 Consequently, they have been proposed as qubits for quantum computation 20 – 23 and as components in molecular spintronics devices, 24 , 25 which would exploit their quantum tunneling properties. For such applications, weak couplings of two or more SMMs to each other or to other components of a device are essential, while maintaining the intrinsic single-molecule properties of each SMM, and this represents the main goal of this study.…”

“…The report of supramolecular C–H···Cl hydrogen-bonded pairs of [Mn 4 O 3 Cl 4 (O 2 CEt) 3 (py) 3 ] ( S = 9/2) demonstrated such coupling between two SMMs for the first time, manifested as exchange-biased QTM steps, quantum superposition states, and quantum entanglement of the two SMMs. 17 , 18 , 19 , 26 Several supramolecular dimers, chains, and 3D networks of weakly coupled SMMs connected by hydrogen-bonds have since been reported. 27 – 33 Disadvantages of linkage by hydrogen-bonds, however, are (i) de-aggregation into monomeric units on dissolution, and (ii) the major loss of synthetic control, with all the previously mentioned supramolecular aggregates being discovered serendipitously.…”

Covalently Linked Dimer of Mn3 Single-Molecule Magnets and Retention of Its Structure and Quantum Properties in Solution

“…), and these have been crucial in demonstrating that SMMs also display fascinating quantum phenomena such as quantum tunneling of magnetization (QTM), , quantum phase interference, − spin–spin cross relaxation, and quantum entanglement. − SMMs have consequently been proposed as qubits for quantum information processing − and as components in molecular spintronics devices. , These potential applications of SMMs require the quantum mechanical coupling of two or more SMMs to each other or to other components of a device while maintaining the intrinsic single-molecule properties of each SMM. Such couplings were successfully identified for hydrogen-bonded supramolecular pairs of S = 9/2 [Mn 4 O 3 Cl 4 (O 2 CEt) 3 (py) 3 ] SMMs and manifested as exchange-biased QTM, quantum superposition states, and quantum entanglement of SMMs. − , However, reliance on hydrogen bonding to provide the inter-SMM interactions was a weakness of the previous work, since it is not so easy to control the oligomerization or guarantee retention of the oligomeric structure in solution. We therefore recently extended this work to aggregates of Mn SMMs linked by covalent organic linkages to provide greater control of various aspects of the oligomerization while still targeting molecular oligomers rather than polymers.…”

Nanostructures as the Substrate for Single-Molecule Magnet Deposition

“…Also, by depositing multiple SMMs on the substrate in close proximity, one can create coupled systems that exhibit collective magnetic behavior. The conducting substrate acts as a mediator, allowing for magnetic interactions between adjacent SMMs, leading to phenomena such as magnetic ordering, spin dynamics [ 221 ], and quantum entanglement [ 222 ], which are of great interest for both fundamental research and potential technological applications. All of these promising features incline researchers to investigate SMMs anchored on electrically conducting platforms and explore their behavior not only on gold but also on nanostructured carbon (i.e., graphene, carbon nanotubes, fullerenes, and their derivatives), which is well known for possessing outstanding electrical transport properties, arising mainly because of the monolayer hexagonal arrangement of the carbon atoms, and their sp 2 hybridization [ 223 ].…”