JKU Linz

Vielteilchen Systeme Many Particle Systems

Theoretical Physics Linz

our RESEARCH

Many Particle Theories provide the basis for understanding the macroscopic behavior of vast assemblies of interacting particles starting from their microscopic properties ("ab initio description"). The central goal is to explain observable quantities on the basis of the Hamiltonian.
"Many-body physics has provided a scientific playground of surprise and continuing revolution over the past half century ... the prospects for major conceptual discoveries remain as bright today. "     (P. Coleman, 2003)

at present, our research interests focus on

Quantum Fluids

We develop and apply modern theoretical approaches and computational methods for calculating the collective phenomena of Bose and Fermi liquids. Systems of particular interest are 4He, 3He and the electron liquid, both in 3D as well as in restricted geometries. Our research is primarily based on the (F)HNC and CBF approaches, which allow high precision results without being as computer-time demanding as simulations. In recent calculations we were able to demonstrate the importance of dynamic pair correlations both for bosons and fermions; furthermore we computed the transport currents relevant for scattering experiments.
(The above picture shows the dynamic structure factor of 3He.)

Finite Electron Systems

Major research efforts are underway worldwide for developing new (multiscale) approaches to nanoworld phenomena, such as clusters, fullerenes, quantum dots and quantum rings. Here our research is centered on the development and application of new (TD)DFT methods, including theoretical models as well as new numerical techniques.
We have developed a very fast real space DFT package in 2D as well as in 3D. 4th order splitting operator techniques are used to solve the eigenvalue problem and new methods motivated from many body theory are applied to reduce the number of s-c iterations in the solution of the KS-equations. The program has been successfully applied to the above mentioned systems.
You can download or code for free at www.limerec.net
(The above picture shows the electron density in a buckminster fullerene with an endahedral Mg atom).

Paramagnetism in Superconductors

Superconductivity is generally associated with expulsion of magnetic flux and perfect diamagnetic behavior. The paramagnetic contribution of the electron spins is neglegibly small under usual conditions. However, if one studies a two-dimensional superconductor with magnetic field direction nearly parallel to the conducting planes, one finds a large paramagnetic contribution and a number of very unusual and interesting phenomena such as coexisting line-like and point-like order parameter zeros, stable antivortices, and an unusual pairing mechanism, in higher Landau levels, of the superconducting pair-wave function. These results have been obtained by solving the quasiclassical equations with Zeeman coupling near the upper critical field for arbitrary temperatures.
(The above picture shows a unit cell with two vortices and a single antivortex.)

Prizes:

Erwin Wenzel Preis 2006 (Michael Aichinger)

 
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some recent publications:

M. Aichinger, S.A. Chin, E. Krotscheck, and E. Räsänen, "Effects of geometry and impurities on quantum rings in magnetic fields",  Phys. Rev. B 73, 195310, (2006),     (abstract)

E. Krotscheck and M.D. Miller, "Third sound and stability of thin 3He 4He films",  Phys. Rev. B 73, 134514, (2006),     (abstract)

U. Klein, "Antivortices due to competing orbital and paramagnetic pair-breaking effects",  in "Current Trends in Vortex State Physics",   p.209, Indian Academy of Sciences, Bangalore, (2006)

M. Aichinger, S.A. Chin, and E. Krotscheck, "4th order algorithms for solving local Schrödinger equations in a strong magnetic field",  Comp. Phys. Commun. B 171, 197, (2005),     (abstract)

M. Aichinger and E. Krotscheck, "A fast configuration space method for solving local Kohn Sham equations",  Comp. Mat. Sci. 34, 188, (2005),     (abstract)

U. Klein, "Two-dimensional superconductor in a tilted magnetic field - states with finite Cooper-pair momentum",   Phys. Rev. B 69, 134518, (2004)     (abstract)

M. Aichinger, S. Kilic, E. Krotscheck, and L. Vranjes, "He atoms in carbon nanotubes and nanotube bundles",  Phys. Rev. B 70, 155412, (2004),     (abstract)

J. Boronat, J. Casulleras, V. Grau, E. Krotscheck, and A. Springer, "Effective mass of two-dimensional 3He",  Phys. Rev. Lett. 91, 085302, (2003),     (abstract)

E. Krotscheck and V. Apaja, "Layer- and bulk-roton excitations of 4He in porous media",  Phys. Rev. Lett. 91, 225302, (2003),     (abstract)

V. Apaja, S. Denk, and E. Krotscheck, "Many-body aspects of positron annihilation in the electron gas",  Phys. Rev. B 68, 195118, (2003),     (abstract)

M. Saarela, J. Paaso, E. Krotscheck, and K. Schörkhuber, "Dimers in Two-dimensional 3He-4He Mixtures",  Phys. Rev. Lett. 85, no. 11, 2344, (2000)     (abstract)

E. Krotscheck, M. Saarela, K. Schörkhuber, and R. Zillich, "Concentrations Dependence of the Effective Mass of 3He Atoms in 3He-4He Mixtures",  Phys. Rev. Lett. 80, 4709 (1998)     (abstract)

 
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our TEAM

Guests:

 
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letzte Änderung:  11.10.2009 hmb ;    25.05.09 hbf