Ultrafast laser-induced spin-flip or spin transfer on Ni₃@C₄₈H₃₇ carbon system via Λ processes

Current nanospintronics research seeks to shrink logic devices down to the atomic scale by exploiting the spin degree of freedom as an information carrier. Ultrafast optical manipulation of spins allows both efficient data storage, and, more promising, also performing quantum logic on the molecular system. Here we use ab initio calculations to investigate ultrafast spin processes on the three-magnetic-center Ni₃@C₄₈H₃₇ carbon system. Spin-flip and spin-transfer scenarios are achieved via Λ processes. We exemplarily present two kinds of processes: (i) local-spin-flips on individual Ni atoms. These scenarios are reversible with the use of the same laser pulses. (ii) Long-distance spin-transfer between two Ni atoms, located on opposite ends of the structure. Our calculations indicate that a direct transfer is possible, only if some spin density is also localized on the third Ni atom, which in this case acts as a control switch. If not, then a two-step transfer is necessary. We tentatively attribute this unexpected behavior to the specific geometry of our structure, in which long-distance spin-transfer follows the least resistance path via the magnetic center sitting in between the initial and the final magnetic sites. Additionally, the effect of the magnetic field strength on the spin dynamics processes is investigated. We find that the spin-transfer scenario is preserved, whereas the local spin-flip scenario on a Ni atom can be suppressed under different magnetic field strengths. To further improve the individual addressability of the spin-flip process, double pulses are employed. Finally, we also compute the second-harmonic generation spectrum of our system. Our results represent a further step toward the advancement of laser-controlled molecular nanospintronics devices.