Deconfined quantum criticality and the stability of U (1) spin liquids

• Applicant: Professor Dr. Hagen Kleinert
• Subject Area: Theoretical Condensed Matter Physics
• Term: from 2006 to 2010
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 23896453

Mott insulators exhibit interesting quantum phase transitions. Typical Mott insulators are Heisenberg antiferromagnet such as, for example, the compound La2CuO4, whose ground state is a Néel state. In a Néel state, the SU (2) symmetry of the Hamiltonian is broken. A quantum phase transition to a paramagnetic state occurs by varying a certain characteristic parameter g of the system. In many Mott insulators, the paramagnetic phase breaks the lattice symmetries, leading to a valence bond solid (VBS) or a Peierls states. Also other exotic paramagnetic states are possible such as, for example, the so-called resonating valence bond (RVB) state. Such a pattern of quantum phase transition does not fit in the Landau-Ginzburg paradigm. Possible effective field theories include a compact U (1) gauge field, where topological defects like magnetic monopoles arise. We propose to study these gauge theories, which exhibit many interesting features of high-energy physics models, such as confinement and chiral symmetry breaking.

• DFG Programme: Research Grants