Imaging fractionalized excitations and their impact on magnetic interactions in two-dimensional quantum spin liquids

• Applicant: Dr. Lucas Schneider
• Subject Area: Experimental Condensed Matter Physics
• Term: since 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 529232793

The physics of quantum spin liquids (QSLs) and their fractionalized quasiparticle excitations has fascinated scientists for decades but is difficult to probe experimentally. Interacting spins in conventional magnetic materials order at sufficiently low temperatures, leading to quasi-classical magnetic ground states such as ferromagnetism, antiferromagnetism, and helical order. In contrast, QSLs are exotic states of matter in which competing interactions between spins lead to massive ground state degeneracy. As a consequence, long-range quantum entanglement without long-range magnetic order is found in QSLs, even when approaching absolute zero temperature. Interestingly, the excitations of the QSL state are fractional quasiparticles, such as spinons, visons, or Majorana quasiparticles (MQPs). Renewed interest in QSLs came with the insight that high-temperature superconductivity may emerge from a doped QSL state and that their excitations can have non-Abelian statistics with promising applications for quantum computation. The goal of this proposal is to demonstrate how scanning tunneling microscopy and -spectroscopy combined with electrostatic gating can be used to access the physics of fractionalized quasiparticles and correlated phases in two candidate QSL materials: 1T-Tantalum Diselenide and Alpha Ruthenium Chloride. These materials will be combined with other 2D materials into heterostructures that exhibit novel properties and functionalities. The proposed experiments could potentially lead to the discovery of spinon-mediated magnetic interactions in an electrical insulator, the characterization of a new class of correlation-driven superconductors, as well as real-space imaging of QSL-based topologically protected MQPs.

• DFG Programme: WBP Fellowship
• International Connection: USA
• Host: Professor Dr. Michael F. Crommie, Ph.D.