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Research topics

Low-dimensional materials and Charge and Spin density waves

Dielectric spectroscopy lab

Besides more conventional materials there exist also low-dimensional ones. These may be artificially produced systems, like thin films or quantum wires and dots which in a technical manner approach lower dimensional realm. But these may be also 3D materials whose electronic, magnetic and other properties are inherently highly anisotropic, giving them prevalently quasi-2D or even quasi-1D character. Already several decades ago quasi-1D materials were sought after in regard of Froehlich's suggestion of a novel superconductivity mechanism. Indeed such materials were synthesized, being metals, semiconductors or insulators along their principal axis. Different material families over the years showed low-dimensional properties: polymers, organic charge-transfer salts, transition metal chalcogenides. While superconductivity of Froehlich's type was not found, these materials featured novel collective electronic ground states: charge and spin density waves and even superconductivity of novel origins. In close analogy with superconductivity, CDW and SDW feature charge carriers, paired and condensed below a gap into a collective quantum state which extends macroscopically across the bulk of the material. However, CDW and SDW are insulating phases, as their condensate is pinned to impurities background and not able to move freely, even when it gets depinned and starts to slide nonlinearly as large electric fields are applied. Still, their fundamental analogies and ever occurring proximity to superconductivity in the phase diagrams of low-dimensional materials gave them important role in the quest for room-temperature superconducting materials. Recently, related novel phases are being identified like charge, orbital and spin orderings in low-dimensional materials where carriers appear to be localized and strongly correlated, and not forming bands as in conventional CDW and SDW.

Self-organised structures

Self-organization is a powerful concept, which recognizes a network pattern of organization with internal non-linear relationships as the basic feature of life and reality. The key criteria of self-organization were discovered in various contexts about 50 years ago, mainly in biological and social structures. Today, scientists are more and more fascinated by this concept discovering its manifestation in distinct kinds of novel materials. Self-organization has been generally defined as the process, in which the organization of complex systems (open systems far from equilibrium) is being created, reproduced and improved. It involves the spontaneous emergence of new structures and new forms of behaviour, characterized by internal feedback loops and described mathematically by non-linear equations.

Life sciences and biotechnology

One role for physicists here is trying to understand the physics of organized molecular systems. DNA and other biologically active polymers, when in natural medium, in aqueous surroundings, they become charged molecules, polyelectrolytes, influenced by the electrostatics of their counterion atmospheres. Also due to the fact that polymers are low dimensional systems, strong charge correlation effects influence their behavior. Complex charge correlations regulate conformations of macromolecules and self-organization of functional molecular aggregates. This enables orderly execution of biological processes, e.g. genome replication.

Laboratories and techniques

Laboratory for Galvano-Magnetic Measurements

  • ac and dc Conductivity
  • I-V Characteristics
  • Magnetoresistance, Hall Effect (superconducting magnet 6 T)

Laboratory for Dielectric Spectroscopy in Solid State

  • Low-Frequency Dielectric Spectroscopy
  • dc Electric Field Dependent Measurements
  • Fourier Analysis of the Narrow-Band Noise

Laboratory for Dielectric Spectroscopy in Life Sciences

  • Low-Frequency Dielectric Spectroscopy of samples in liquid solution
  • pH/conductivity measurements
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