Project Details
Projekt
FOR 960: Quantum Phase Transitions
Subject Area
Physics
Term
from 2007 to 2015
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 48554140
One of the most promising routes towards novel states of matter and functional materials with new properties is the investigation of compounds where several phases (e.g., magnetic and nonmagnetic, conducting and insulating) compete with each other. This competition is manifest near a quantum phase transition, where the system switches from one ground state to another. Quantum phase transitions (QPTs) are phase transitions that occur in a strict sense only at temperature T = 0 can be tuned by a control parameter such as pressure or magnetic field. As opposed to a classical phase transition at finite temperature, quantum effects play a decisive role, as the fluctuations driving the transition follow quantum instead of classical statistical mechanics. Having been considered for a long time as a mere curiosity of theoretical physics, the impact of this field on physics is now emerging with steadily increasing pace. German groups have made major contributions to this new area of condensed matter physics. The Research Unit intends to strengthen their prominent role.
Quantum fluctuations near a QPT affect the finite-temperature behaviour of condensed matter as well, with a multiplicity of new and unexpected phenomena. For instance, the standard model of metals with electronic interactions, the Landau Fermi-liquid picture, breaks down in the vicinity of a magnetic QPT. In addition, since QPTs occur between nearly degenerate phases whose characteristic energies or energy differences are driven to zero, new small energy scales may become important, which would be otherwise masked by the primary energy scales. This has the prospect of finding novel phases.
In the Research Unit we focus on quantum phase transitions in electronic systems, e.g., systems where the electronic, magnetic and lattice properties are governed by the occurrence of a QPT induced by a loss of magnetic moments due to electronic interactions or competing frustrated interactions. In a collaborative effort of experiment and theory, we study several classes of matter at QCPs: intermetallic f-electron compounds, weak itinerant transition-metal magnets and transition-metal oxides and sulfides. The issue at stake is experimentally and theoretically challenging. The wide range of materials to be investigated will help to separate materials-related issues from fundamentally new physics. Participating Research Institutions are: University of Augsburg, Max Planck Institute for Chemical Physics of Solids Dresden, University of Göttingen, University of Karlsruhe, Forschungszentrum Karlsruhe, University of Cologne, Technische Universität München and the Ludwig-Maximilians-Universität München.
Quantum fluctuations near a QPT affect the finite-temperature behaviour of condensed matter as well, with a multiplicity of new and unexpected phenomena. For instance, the standard model of metals with electronic interactions, the Landau Fermi-liquid picture, breaks down in the vicinity of a magnetic QPT. In addition, since QPTs occur between nearly degenerate phases whose characteristic energies or energy differences are driven to zero, new small energy scales may become important, which would be otherwise masked by the primary energy scales. This has the prospect of finding novel phases.
In the Research Unit we focus on quantum phase transitions in electronic systems, e.g., systems where the electronic, magnetic and lattice properties are governed by the occurrence of a QPT induced by a loss of magnetic moments due to electronic interactions or competing frustrated interactions. In a collaborative effort of experiment and theory, we study several classes of matter at QCPs: intermetallic f-electron compounds, weak itinerant transition-metal magnets and transition-metal oxides and sulfides. The issue at stake is experimentally and theoretically challenging. The wide range of materials to be investigated will help to separate materials-related issues from fundamentally new physics. Participating Research Institutions are: University of Augsburg, Max Planck Institute for Chemical Physics of Solids Dresden, University of Göttingen, University of Karlsruhe, Forschungszentrum Karlsruhe, University of Cologne, Technische Universität München and the Ludwig-Maximilians-Universität München.
DFG Programme
Research Units
Projects
- Dynamics of Correlated Electrons at Quantum Phase Transitions (Applicants Bulla, Ralf ; Kehrein, Stefan )
- Heavy-fermion metals and Kondo criticality (Applicants Bulla, Ralf ; Vojta, Matthias ; Wölfle, Peter )
- Multiple scales and exotic criticality near quantum phase transitions (Applicant Garst, Markus )
- Quantum critical point scenarios in heavy-fermion systems (Applicants Gegenwart, Philipp ; Steglich, Frank )
- Quantum criticality in transition-metal oxides and chalcogenides and in frustrated lattices (Applicant Büttgen, Norbert )
- Quantum phase transitions in frustrated magnetic systems (Applicant Wölfle, Peter )
- Role of the tuning parameter at magnetic quantum phase transitions (Applicants von Löhneysen, Hilbert ; Stockert, Oliver )
- Spin dynamics and spin freezing at ferromagnetic quantum phase transitions (Applicant Pfleiderer, Christian )
- Tuning the competition between ground states in transition-metal oxides by uniaxial pressure (Applicant von Löhneysen, Hilbert )
- Zentralprojekt (Applicant von Löhneysen, Hilbert )
Spokesperson
Professor Dr. Hilbert von Löhneysen
