Correlated fermion quantum criticality

• Applicant: Dr. Philipp Strack
• Subject Area: Theoretical Condensed Matter Physics
• Term: from 2010 to 2014
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 188601717

The overall goal of this proposal is to contribute to a consistent understanding of correlated Fermi-systems in the vicinity of quantum phase transitions. Quantum phase transitions are driven by quantum ("zero-point") fluctuations at zero temperature and are currently a very active field in theoretical condensed matter physics and physics in general. Since quantum phase transitions differ significantly from thermal phase transitions, new theories (models and methods) are necessary to describe them.Specifically the physical focus of this proposal rests on three topics: (i) polarized Fermi gases in optical lattices, (ii) quantum critical fluctuations in systems with ("Pomeranchuk-") Fermi surface deformations, and (iii) quantum critical fluctuations in (antiferro-) magnetic systems. In all of these topics, the characterizing properties of quantum phase transitions, such as the critical exponents, the categorization into new universality classes, and an analysis of the order of the transitions (first vs. second order) under inclusion of fluctuations, will be investigated.To compute these characterizing properties, new quantum field theoretical methods need to be developed and applied. Next to the singularities and the divergence of the correlation length, which occur also at thermal phase transitions, at quantum phase transitions the interaction between the quasi-particles (fermions) and the order parameter (bosons) leads to very interesting and novel, but also complicated phenomena. Methodically, the development of quantum field theoretical tools which describe the interplay of fermions and bosons at quantum criticality are at the center of this proposal.

• DFG Programme: Research Fellowships
• International Connection: USA
• Host: Professor Dr. Subir Sachdev