Observation of Tunneling-Assisted Highly Forbidden Single-Photon Transitions in a Ni_{4} Single-Molecule Magnet.
Forbidden transitions between energy levels typically involve violation of selection rules imposed by symmetry and/or conservation laws. A nanomagnet tunneling between up and down states violates angular momentum conservation because of broken rotational symmetry. Here we report observations of highly forbidden transitions between spin states in a Ni_{4} single-molecule magnet in which a single photon can induce the spin to change by several times ℏ, nearly reversing the direction of the spin. These observations are understood as tunneling-assisted transitions that lift the standard Δm=±1 selection rule for single-photon transitions. These transitions are observed at low applied fields, where tunneling is dominated by the molecule's intrinsic anisotropy and the field acts as a perturbation. Such transitions can be exploited to create macroscopic superposition states that are not typically accessible through single-photon Δm=±1 transitions.
Department of Physics and Astronomy, Amherst College, Amherst, Massachusetts 01002-5000, USA.|Department of Physics, University of Massachusetts, Amherst, Massachusetts 01003, USA.
Yiming
Y
Chen
Department of Physics and Astronomy, Amherst College, Amherst, Massachusetts 01002-5000, USA.
Mohammad D
MD
Ashkezari
Department of Physics and Astronomy, Amherst College, Amherst, Massachusetts 01002-5000, USA.
Charles A
CA
Collett
Department of Chemistry, University of Massachusetts, Amherst, Massachusetts 01003, USA.
Rafael A
RA
Allão Cassaro
S3 Instituto Nanoscienze-CNR, I-41124 Modena, Italy.
Filippo
F
Troiani
Department of Chemistry, University of Massachusetts, Amherst, Massachusetts 01003, USA.
Paul M
PM
Lahti
Department of Physics and Astronomy, Amherst College, Amherst, Massachusetts 01002-5000, USA.
Jonathan R
JR
Friedman