Emergent symmetry in lithium molybdate (LMO)

Upon cooling, condensed matter systems typically transition into states of lower symmetry. While the converse, i.e. the emergence of higher symmetry at lower temperatures, has been hypothesized, it is extremely rare. Here, we show how an unusually isotropic 25 magnetoresistance in the highly anisotropic, one-dimensional conductor Li0.9Mo6O17 (LMO), and its temperature dependence, can be interpreted as a renormalization group (RG) flow towards a so-called separatrix. This approach is equivalent to an emergent symmetry in the system. The existence of two distinct ground states – Mott insulator and superconductor – can then be traced back to two opposing RG trajectories. By establishing a direct link between quantum field theory 30 and an experimentally measurable quantity, we uncover a path through which emergent symmetry might be identified in other candidate materials.