Quantum criticality in an Ising chain: experimental evidence for emergent E8 symmetry

Understand

Quantum phase transitions take place between distinct phases of matter at zero temperature.

• Near the transition point, exotic quantum symmetries can emerge that govern the excitation spectrum of the system.
• A symmetry described by the E8 Lie group with a spectrum of 8 particles was long predicted to appear near the critical point of an Ising chain.
• We realize this system experimentally by tuning the quasi-one-dimensional Ising ferromagnet CoNb2O6 through its critical point using strong transverse magnetic fields.