309186 20240928181507.0 G:(GEPRIS)35758978 G:(GEPRIS)35758978 35758978 GEPRIS http://gepris.its.kfa-juelich.de Quantum criticality: coupled renormalization of electrons and order parameter fluctuations 2007 - 2015 Professor Dr. Walter Metzner DFG project G:(GEPRIS)35758978 d 2007 - 2015 Deutsche Forschungsgemeinschaft I:(DE-588b)2007744-0 DFG G:(GEPRIS)21278441 FOR 723: Functional Renormalization Group in Correlated Fermion Systems t In this project we study several types of quantum phase transitions in interacting Fermi systems, between a symmetric phase and an ordered phase with spontaneously broken symmetry. These include the nematic transition in metals, a normal to superfluid transition in semi-metals, and chiral symmetry breaking in the (relativistic) Thirring model. The main focus will be on (2+1)-dimensional systems. We are particularly interested in systems for which an effective order parameter theory truncated at quartic order in the fields (Hertz-Millis theory) does not describe the low energy behavior correctly. The functional RG will be used to analyze the coupled system of electronic excitations and order parameter fluctuations, that is, fermions and bosons will be integrated out simultaneously. We will try to derive and solve a set of flow equations which properly treats all the entangled singularities appearing near the quantum phase transition. We will access all regions of the phase diagram, including the symmetry-broken regime and regimes governed by non-Gaussian fluctuations. We will take full advantage of the possibilities of the functional RG by allowing also for truly functional flows, such as flows of the fullo rder parameter potential, capturing vertices with arbitrary powers of the fields. oai:juser.fz-juelich.de:976061 authority:GRANT authority G AUTHORITY oai:juser.fz-juelich.de:976061