The first theoretical proof that an atomically thin material, α-RuCl3, may
be controlled only by inserting it into an optical cavity has been generated
by researchers in the U.S. and Germany. Crucially, the material's magnetic
order can be converted from a zigzag antiferromagnet to a ferromagnet only
by the cavity vacuum fluctuations. The publication of the team's work may be
found
in npj Computational Materials.
Using strong laser light to change the characteristics of magnetic
materials has become a popular issue in material physics study recently.
Through careful manipulation of the laser light's characteristics,
scientists have significantly altered the electrical conductivity and
optical characteristics of several materials.
However, this comes with several practical issues, chief among them being
the difficulty of stopping the material from heating up, and necessitates
constant stimulation by high-intensity lasers. So, instead of utilizing
powerful lasers, researchers are searching for ways to use light to
influence materials in a similar way.
Theorists at the University of Pennsylvania, Stanford University, and the
Max Planck Institute for the Structure and Dynamics of Matter (MPSD) in
Hamburg, Germany have now developed a radically new method for altering a
real material's magnetic properties in a cavity without the use of laser
light. Their cooperation demonstrates that the zigzag antiferromagnet
α-RuCl3 may become a ferromagnet just by virtue of the cavity.
Most importantly, the group shows that α-RuCl3 recognizes changes in the
electromagnetic environment and modifies its magnetic state appropriately,
even in a seemingly dark hollow. This effect is solely of a quantum
mechanical nature, stemming from the fact that the vacuum state, also known
as the empty cavity, is never truly empty in quantum theory. Rather, the
light field varies, causing light particles to appear and disappear, which
in turn modifies the material's characteristics.
Lead author Emil Viñas Boström, a postdoctoral researcher in the MPSD
Theory Group, says, "The optical cavity confines the electromagnetic field
to a very small volume, thereby enhancing the effective coupling between the
light and the material." "Our results show that carefully engineering the
vacuum fluctuations of the cavity electric field can lead to drastic changes
in a material's magnetic properties." Since there is no requirement for
light excitation, the method theoretically avoids the issues related to
continuous laser driving.
This work, which builds on earlier studies into cavity control of
ferroelectric and superconducting materials, is the first to demonstrate
such control over magnetism in a genuine material. By creating precise
chambers, the scientists aim to better comprehend the complex interactions
between light and matter and reveal previously undiscovered phases of
matter.
