Evolving Devil's Staircase Magnetization from Tunable Charge Density Waves in Nonsymmorphic Dirac Semimetals

While several magnetic topological semimetals have been discovered in recent years, their band structures are far from ideal, often obscured by trivial bands at the Fermi energy. Square‐net materials with clean, linearly dispersing bands show potential to circumvent this issue. CeSbTe, a square‐net material, features multiple magnetic‐field‐controllable topological phases. Here, it is shown that in this material, even higher degrees of tunability can be achieved by changing the electron count at the square‐net motif. Increased electron filling results in structural distortion and formation of charge density waves (CDWs). The modulation wave‐vector evolves continuously leading to a region of multiple discrete CDWs and a corresponding complex “Devil's staircase” magnetic ground state. A series of fractionally quantized magnetization plateaus is observed, which implies direct coupling between CDW and a collective spin‐excitation. It is further shown that the CDW creates a robust idealized nonsymmorphic Dirac semimetal, thus providing access to topological systems with rich magnetism. Fractionally quantized Hall plateaus originate from translational symmetry breaking in 2D systems. It is also possible to observe similar quantization of other physical properties in bulk materials in the presence of coupled collective excitations. Such a state is realized and tuned by changing the electron count in CeSbTe. It also creates an idealized nonsymmorphic Dirac semimetal state in this compound.