Forschungszentrum Jülich
Institut für Festkörperforschung
Institute
Theory III
General
Overview
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The institute Theory III investigates the mechanisms of the formation of structures and their consequences in condensed matter. The research starts from electronic properties which define the shortest length and time scales, but it also encompasses the macroscopic consequences. The analytical and numerical investigations are in many ways closely connected with experimental studies performed in other groups of the IFF, and also with activities in other institutes of the Research Center Jülich. Central points of interest for the research in Theory III are in the field of electronic structure of solids. Material classes under consideration are metals, semiconductors and related nanostructured materials specifically with respect to their importance for information technology. A second mainstream is formed by cooperative phenomena in condensed matter. Questions here aim at the dynamics of structure and pattern formation and the statistical mechanics of order and disorder processes. Specific activities concern the effect of long-range interactions like elastic effects in solids or hydrodynamic interactions in solid-liquid systems. The research of Theory III employs a wide range of analytical and numerical techniques applicable to many-body problems in condensed matter. In addition the development of new methodological concepts and numerical procedures is part of our research interest. The development of parallel program codes adapted to massively parallel computers has received special attention in recent years. The explanation of the microstructure and dynamics of real solids requires the understanding of the electronic properties. One of the most important methods for the calculation of the electronic structure of real solids is the density functional theory in connection with appropriate numerical procedures. While in recent years bulk properties of metals and semiconductors have been at the center of our interest a main concern now is directed towards the understanding of surface and interface properties, with particular emphasis on magnetism. Theoretical efforts in the investigation of electronic effects, combining charge and spin properties for a future technology based on spin-electronics, presently are centered on the problem of spin-injection. Spin-injection is a prerequisite for semiconductor spin-electronics. We have considered spin-injection from Fe into ZnSe and GaAs in the ballistic limit. By means of the ab-initio SKKR method the ground state properties of epitaxial Fe/ZnSe and Fe/GaAs heterostructures were calculated. Three different injection processes were considered. The calculation of the electrical conductance shows that (001)-interfaces may act as almost ideal spin-filters, while other orientations give only small injection efficiencies. The high spin polarization can be traced back to symmetries of the bandstructure of iron. The properties of high-tech materials for sensorics and information-technology depend usually on details of their surface structures and on the growth processes of these materials. The surface of the growing interface is often covered with a passivating material like Sb, in order to achieve layered growth rather than island growth. We can explain the experimentally observed development of surface structures of a growing Ge film on Si(111), covered with a monatomic layer of Sb. For this purpose an ab-initio method (the Jülich EStCoMPP-code) was used for the calculation of the stability of different Ge(111):Sb structures. As one example, the (1x1) substitutional structure experimentally found on top of the Sb-covered hexagons, formed for a three-monolayer Ge film deposited on Si(111), can be traced back to an over-relaxation of the finite size hexagons caused by the Sb atoms on top and at the edge of the hexagons. Glasses have properties with characteristic anomalies in comparison with regular solids or with liquids. Particularly significant is the so-called Boson-peak in the phonon-spectrum at low frequencies. A universal mechanism of Boson-peak formation in glasses has now been proposed. It is based on the concept of interacting quasi-local oscillators. Even in the case of weak interaction the ordinary low frequency-spectrum becomes unstable. Due to anharmonicity the system undergoes a transition into a new stable configuration. Below some characteristic frequency the renormalized density of states becomes a universal function of the frequency with Boson-peak characteristics. An analytical form of this function has been derived. The formation of alloys in directional solidification and the appearance of structures in liquids may exhibit striking similarities. The phase transformation of a two-component liquid during condensation in a distillation apparatus is discussed. The liquid is assumed to flow in a temperature gradient towards decreasing temperature. Two different phase diagrams are considered. For a binary fluid with a critical point the separation occurs via spinodal decomposition as a convective instability. For a cigar-shaped phase diagram the phase-transformation is shown to evolve in analogy to the fingering-processes known from directional solidification. Solids crack when the stresses are getting too strong. A satisfactory explanation for the dynamics of crack propagation has been missing so far. We present a continuum theory which describes the fast growth of a crack by surface diffusion. This mechanism overcomes the usual cusp singularity by a self-consistent selection of the radius of the crack tip. It is found that the maximal steady state crack velocity remains appreciably below the Rayleigh speed, while the crack-tip becomes blunt. Furthermore the theory suggests the possibility of a tip splitting instability for high applied tensions. H. Müller-Krumbhaar, January 2003.
Personnel 2002/2003 and areas of activity
Publications in journals Antons,A.;
Schroeder,K.; Voigtländer,B.; Cherepanov,V.; Berger,R.; Blügel,S. Baranov,A.
N.*; Stepanyuk,V.S.*; Hergert,W.*; Katsnelson,A. A.*; Settels,A.;
Zeller,R.; Dederichs,P.H. Brener,E.;
Kessler,D.* Brener,E.;
Marchenko,V.* Brener,E.;
Temkin,D.* Cabria,I.;
Nonas,B.; Zeller,R.; Dederichs,P.H. Cao,Y.;
Zheng-Kuan,J.*; Antons,A.; Schroeder,K.; Blügel,S. Cao,Y.;
Zheng-Kuan,J.*; Antons,A.; Schroeder,K.; S. Blügel,S. Caprion,D.*;
Schober,H. R. Dederichs,P.H.;
Mavropoulos,Ph.; Wunnicke,O.; Papanikolaou,N.; Bellini,V.; Zeller,R.;
Drchal,V.*; Kudrnovsky,J.* Drchal,V.*;
Kudrnovsky,J.*; Bruno,P.*; Dederichs,P. H.; Turek,I.*; Weinberger,P.* Freyss,M.;
Mavropoulos,P.; Papanikolaou,N.; Bellini,V.; Zeller,R.; Dederichs,P.H. Freyss,M.;
Papanikolaou,N.; Bellini,V.; Zeller,R.; Dederichs,P. H. Freyss,M.;
Papanikolaou,N.; Bellini,V.; Zeller,R.; Dederichs,P.H.; Turek,I.* Galanakis,I.;
Bihlmayer,G.; Bellini,V.*; Papanikolaou,N.*; Zeller,R.; Blügel,S.;
Dederichs,P.H. Galanakis,I.;
Papanikolaou,N.; Dederichs,P. H. Gurevich,V.*;
Parshin,D.A.*; Schober,H. R. Gurevich,
V.L., Parshin, D.A., Schober, H.R. Hartmann,M.;
Trinkaus,H. Hauck,J.;
Erkens,W.; Mika,K.; Wingerath,K. Hirnet,A.*;
Schroeder,K.; Blügel,S.; Torrelles,X.*; Albrecht,M.*; Jenichen,B.*;
Gierer,M.*; Moritz,W.* Kudrnovsky,J.*;
Drchal,V.*; Turek,I.*; Dederichs,P. H.; Weinberger,P.*; Bruno,P.* Levy,P.
M.*; Wang,K.*; Dederichs,P. H.; Heide,C.*; Zhang,S.*; Szunyogh,L.* Luysberg,M.;
Kirch,D.; Trinkaus,H.; Holländer,B.; Lenk,St.; Mantl,S.; Herzog,H.-J.*;
Hackbarth,T.*; Fichtner,P.F.P.* Mavropoulos,Ph.;
Wunnicke,O.; Dederichs,P.H. Müller-Krumbhaar,H.;
Abel,T.; Brener,E.; Hartmann,M.; Eissfeldt,N.; Temkin,D.* Papanikolaou,N.;
Zeller,R.; Dederichs,P.H. Rzehak,R.;
Zimmermann,W.* Schober,H.
R. Schober,H.R. Schober,H.R. Schroeder,K.;
Antons,A.; Berger,R.; Blügel,S. Schroeder,K.;
Antons,A.; Berger,R.; Blügel,S. Schroeder,K.;
Antons,A.; Berger,R.; Blügel,S. Trinkaus,H.;
Heinisch,H. L.*; Barashev,A. V.*; Golubov,S.I.*; Singh,B.N.* Trinkaus,H.;
Ullmaier,H. Turek,I.*;
Kudrnovsky,J.*; Drchal,V.*; Weinberger,P.*; Dederichs,P.H. Turek,I.*;
Kudrnovsky,J.*; Drchal,V.*; Weinberger,P.*; Dederichs,P.H. Wunnicke,O.;
Mavropoulos,Ph.; Zeller,R.; Dederichs,P.H.; Grundler,D.* Wunnicke,O.;
Papanikolaou,N.; Zeller,R.; Dederichs,P.H.; Drchal,V.*; Kudrnovsky,J.* Book
chapter Schober,H.
R.; Caprion,D.* Atodiresei,N.;
Kromen,Wi.; Blügel,S.; Schroeder,K. Brener,E.;
Marchenko,V.* Brener,E.;
Spatschek,R. Brener,E.;
Spatschek,R. Brener,E.;
Spatschek,R. Brener,E.;
Spatschek,R. Brener,E.;
Temkin,D.* Dederichs,P.
H. Dederichs,P.
H. Dederichs,P.
H. Dederichs,P.
H. Dederichs,P.H. Galanakis,I. Galanakis,I.;
Dederichs,P. H. Golubov,S.*;
Singh,B.*; Trinkaus,H. Höher,H.;
Zeller,R.; Dederichs,P. H. Mavropoulos,Ph.;
Galanakis,I.; Dederichs,P.H. Sato,K.;
Katayama-Yoshida,H.* Sato,K.;
Katayama-Yoshida,H.*; Dederichs,P. H. Sato,K.;
Katayama-Yoshida,H.*; Dederichs,P. H. Schober,H.
R. Schober,H.
R. Schober,H.
R. Schober,H.
R.; Caprion,D.* Schober,H.
R.; Gurevich,V. L.*; Parshin,D. A.* Schroeder,K.;
Antons,A.; Berger,R.; Blügel,S. Trinkaus,H. Trinkaus,H. Trinkaus,H. Trinkaus,H.;
Singh,B.* Wunnicke,O.;
Mavropoulos,P.; Zeller,R.; Dederichs,P.H.; Grundler,D.* Wunnicke,O.;
Mavropoulos,P.; Zeller,R.; Dederichs,P.H.; Grundler,D.* Wunnicke,O.;
Mavropoulos,P.; Zeller,R.; Dederichs,P.H.; Grundler,D.* Wunnicke,O.;
Mavropoulos,P.; Zeller,R.; Dederichs,P.H.; Grundler,D.* Zeller,R.
Brener,E.;
Spatschek,R. Dederichs,P.
H. Gutheim,F.;
Müller-Krumbhaar,H. Mavropoulos,P.;
Wunnicke,O.; Dederichs,P.H. Rzehak,R.;
Kienle,D.*; Zimmermann,W.* Sato,K.;
Katayama-Yoshida,H.* Schober,H.
R. Schober,H.
R.; Caprion,D.* Schroeder,K. Spatschek,R.;
Brener,E.
Antons,A.;
Schroeder,K.; Berger,R.; Blügel,S. Brener,E.;
Marchenko,V.* Galanakis,I.;
Dederichs,P.H. Gurevich,V.
L.*; Parshin,D. A.*; Schober,H. R. Rzehak,R.;
Müller-Krumbhaar,H.; Marquardt,W.* Rzehak,R.;
Zimmermann,W.* Sato,K.;
Katayama-Yoshida,H.* Sato,K.;
Katayama-Yoshida,H.* Sato,K.;
Katayama-Yoshida,H.*; Dederichs,P. H. Sato,K.;
Katayama-Yoshida,H.*; Dederichs,P.H. Schober,H.
R.; Kluge,M.; Caprion,D.* Wunnicke,O. Wunnicke,O.;
Mavropoulos,P.; Zeller,R.; Dederichs,P.H.; Grundler,D.* Wunnicke,O.;
Mavropoulos,Ph.; Zeller,R.; Dederichs,P.H. Wunnicke,O.;
Mavropoulos,Ph.; Zeller,R.; Dederichs,P.H. Wunnicke,O.;
Papanikolaou,N.; Zeller,R.; Dederichs,P.H.; Drchal,V.*; Kudrnovsky,J.* Antons,A. Berger,R. |
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