Transition between two metallic ferroelectric orders in multiferroic Ca${}_3$Ru${}_2$O${}_7$, induced by magnetism-mediated orbital re-polarization

Zheting Jin, Wei Ku

For the past decades, the low-temperature phase of Ca${}_3$Ru${}_2$O${}_7$ below the 48K first-order phase transition remains a puzzle with controversial suggestions involving metallic f…