Research Topics - Forschung

Activities of the group: (Kurzzusammenfassung) (Short Summary)


Complex and nanostructured materials




light - matter interaction and electronic reconstruction in nanoscale systems and metamaterials


large cross susceptibilities in inhomogeneous matter


novel sensor applications and information storage concepts: bistable molecules in templates

In detail:


Tip-enhanced scattering on templated molecules
A novel light scattering technique based on the combination of Raman scattering and an atomic force microscope is implemented and used on single molecular magnets and buried molecules in nanoporous templates. -> TERS LAB


Elastic and magnetic properties of nanocomposites
Nanocomposites have an exceptional large internal surface that supports the coupling of different order parameters. Plasma sparc sintering allows the preparation of uniform bulk materials with a well defined length scales in the nm range, complex nanostructures and exceptional mechanical and electronic properties. Investigations are performed together with groups from the Inst. of Inorganic Chemistry, Univ. Stockholm and the MPI-FKF Stuttgart. -> US LAB


Coupling of FM and FE order parameters
Mutual exclusive order parameters can be coupled leading to new functionalities as observed in multiferroics. Such a behavior is presently studied in nanoscale composites (meta materials), incommensurate antiferromagnets and lone pair compounds. Work is performed in collaboration with groups from the Univ. of Augsburg, Chisinau and the TU Braunschweig.


Doping of correlated oxides and molecular systems
Phase diagrams with competing states, phase separation or unusual criticality are observed. The resulting soft electronic modes lead to colossal response to external magnetic or electric fields. Low energy intermolecular modes critically affect the spin state of the molecular systems. Work is performed in collaboration with groups from the university of Frankfurt, Erlangen and Bielefeld.



colossal magnetoresistance, magnetocapacitace, thermopower in manganites, thiospinels and cobaltates


Interdisciplinary material research:
Physics/chemistry data base search for novel functional material


Interdisciplinary approach to characterize and develop novel preparation concepts:

- electrochemical preparation of nanoporous systems
- plasma sparc sintering of nanoscale composites
- magnetic host-guest compounds

We acknowledge financial support by DFG (projects and topical centers), ESF, Vinnova, and the NMWK.





Magnetism, electronic correlations and competing interactions

Interrelation of spin, orbit and topology

on small length scales



Unusual criticality in low dimensions and due to competing interactions


Bose-Einstein transition of diluted magnons
(Ultrasonic spectroscopy)


Giant response of the lattice system


Geometrically frustrated systems and competing interactions






Introduction to magnetism and correlated electron systems


magnetism & electronic correlations in systems with restricted or confined geometries


structural principles of transition metal oxides:
spin chains, spin ladders, 2D topologies und tetrahedra 


some interesting transition metal oxides 


collective magnetic excitations and  bound states


spin defects and doping of quantum spin systems


spin frustration and competing interactions  


stripe phases und orbital degrees of freedom


quantum critical behavior 


Experimental Techniques:  

- optical spectroscopies and apertureless Raman scattering

- preparation and search for NEW MATERIALS (Database mining)

- ultrasonic spectroscopy


Recent Seminars:  

- "Quantum Magnetism in Novel Materials and Geometries", (1999)

- IGSM Lecture on Superconductivity

- Magnetismus und Datenspeicherung (populärwiss. VL, "Physik am Samstag")

- Habilitation colloquium "Sonolumineszenz - Aus Schall wird Licht" (1999)

- Übersicht zum DFG-Schwerpunkt SPP 1073, "Kollektive Quantenzustände in
  elektronisch 1D Übergangsmetall-Verbindungen
" (2000) 

- Frühjahrstagung der DPG in Hamburg (2001)

- Frühjahrstagung der DPG in Regensburg (2002)

- Frühjahrstagung der DPG in Dresden (2003)

- Frühjahrstagung der DPG in Regensburg (2004)

- Frühjahrstagung der DPG in Berlin (2005)

- Frühjahrstagung der DPG und der EPS in Dresden (2006)

- Frühjahrstagung der DPG in Dresden (2007)

- Frühjahrstagung der DPG in Berlin (2008)

- lectures and seminars

- recent lecture materials


Further Contributions:

- publications

- running projects and proposals

- important links


Webpages of Peter Lemmens

Diese Web-Seite stellt keine Meinungsäußerung der TU Braunschweig dar.     

p.lemmens at, letzte Änderung: 24.04.2009