2026 Theses Doctoral

Controlling Magnetism and Charge Order in Intercalated van der Waals Materials

Feuer, Margalit L.

Charge and spin are two fundamental aspects of electrons, the behaviors of which underpin many quantum properties. This dissertation dissects their interaction in two dimensional (2D) materials and quasi-one dimensional (1D) materials, mainly by interrogating the van der Waals material CrSBr. The conduction-band orbitals of this system forces an intrinsic and unusual coupling between charge and spin confined to one dimension.

Chapter 1 introduces layered materials generally and reviews CrSBr in specific. The strong coupling between various degrees of freedom in CrSBr are surveyed to serve as a foundation for the subsequent chapters. Chapter 2 investigates how chemical doping of CrSBr manipulates both the magnetic and charge orders. Doping produces Li-CrSBr, a material with a quasi-1D charge denstiy wave (CDW) coupled to enhanced ferromagnetism coupled through spin-polarized conduction bands. Chapter 3 dissects how the charge order affects other properties of Li-CrSBr. The intrinsic coupling between the CDW and the magnetic order is investigated through pump-probe spectroscopy. Further, 1D plasmons in Li-CrSBr are explored. Chapter 4 investigates the coupling between the charge and magnetic ordering by tuning the doping level. This is undertaken first from a theoretical approach and then borne out through experiment where a lower doping level produces a colder magnetic ordering temperature and dynamic charge ordering.

Lastly, Chapter 5 broadens these methodologies to a structurally analogous family of materials to CrSBr: LanSI, Lan = Dy or Gd. Chemical intercalation is used to manipulate the structures and enhance the magnetic orders of these materials. The coupling of spin, charge, structure and orbitals are considered. Together, this body of works explores the chemical levers for manipulating multiple degrees of freedom in bulk layered materials, essential for producing materials with quantum properties, such as magnetoresistance, and integration into device architectures for spintronic and memory devices applications.