Abstract
Manipulating symmetry environments of metal ions to control functional properties is a fundamental concept of chemistry. For example, lattice strain enables control of symmetry in solids through a change in the nuclear positions surrounding a metal centre. Light–matter interactions can also induce strain but providing dynamic symmetry control is restricted to specific materials under intense laser illumination. Here, we show how effective chemical symmetry can be tuned by creating a symmetry-breaking rotational bulk polarisation in the electronic charge distribution surrounding a metal centre, which we term a meta-crystal field. The effect arises from an interface-mediated transfer of optical spin from a chiral light beam to produce an electronic torque that replicates the effect of strain created by high pressures. Since the phenomenon does not rely on a physical rearrangement of nuclear positions, material constraints are lifted, thus providing a generic and fully reversible method of manipulating effective symmetry in solids.
Highlights
Manipulating symmetry environments of metal ions to control functional properties is a fundamental concept of chemistry
Polarised light (CPL) can induce symmetry reduction in chemical environments of photoactive materials[8,9,10,11], an ability that is associated with its inherent sense of handedness, a property known as chirality, conveyed by its intrinsic spin angular momentum
We propose that the effect arises from a transfer of optical spin angular momentum from a chiral light beam through an interfacial mechanism
Summary
Manipulating symmetry environments of metal ions to control functional properties is a fundamental concept of chemistry. By analogy with the crystal field established by ligands around a coordinated metal ion, the bulk polarisation effectively acts as a “meta-crystal field” to create an electrostatic potential that acts as a second-order perturbation on the symmetry environment of the metal centres. This effect is considered to be generic for ionic inorganic films containing transition and lanthanide metal ion centres. We use chiral nanostructures to modulate the amount of spin angular momentum transferred to the Eu2O3 films In both cases, symmetry reduction is reversible because the electronic torque is removed when the light is switched off. Experimental results are complemented with numerical finiteelement simulations allowing the spin transfer to be quantified directly, demonstrating this effect as the cause of changes in Eu3+
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