Imperial College London

Professor SirJohnPendry

Faculty of Natural SciencesDepartment of Physics

Chair in Theoretical Solid State Physics
 
 
 
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Contact

 

+44 (0)20 7594 7606j.pendry Website CV

 
 
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Assistant

 

Mrs Carolyn Dale +44 (0)20 7594 7579

 
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Location

 

808Blackett LaboratorySouth Kensington Campus

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Summary

 

Summary of research

John Pendry is a condensed matter theorist. He has worked at the Blackett Laboratory, Imperial College London, since 1981. He began his career in the Cavendish Laboratory, Cambridge, followed by six years at the Daresbury Laboratory where he headed the theoretical group. He has worked extensively on electronic and structural properties of surfaces developing the theory of low energy diffraction and of electronic surface states. Another interest is transport in disordered systems where he produced a complete theory of the statistics of transport in one dimensional systems.

 

In 1992 he turned his attention to photonic materials and developed some of the first computer codes capable of handling these novel materials. This interest led to his present research which concerns the remarkable electromagnetic properties of ‘metamaterials’ whose properties owe more to their micro-structure than to the constituent materials. These made accessible completely novel materials with properties not found in nature. Successively metamaterials with negative electrical permittivity, then with negative magnetic permeability were designed and constructed. These designs were subsequently the basis for the first material with a negative refractive index, a property predicted 40 years ago by a Russian scientist, but unrealised because of the absence of suitable materials. He went on to explore the surface excitations of the new negative materials and showed that these were part of the surface plasmon excitations familiar in metals. This project culminated in the proposal for a ‘perfect lens’ whose resolution is unlimited by wavelength.

 

In collaboration with a team of scientists at Duke University, he has developed the concept of ‘transformation optics’, or TO for short, which prescribes how electromagnetic lines of force can be manipulated at will. This enabled a proposed recipe for a cloak that can hide an arbitrary object from electromagnetic fields. Metamaterials give the possibility of building such a cloak and a version of this design working at radar frequencies and exploiting the properties of metamaterials has now been implemented experimentally by the Duke team. Optical versions of the cloak have now been constructed.

 

Electromagnetism provides us with some of the most powerful tools in science, encompassing lasers, optical microscopes, MRI scanners, radar and a host of other techniques too numerous to mention. To understand and develop the technology requires more than a set of formal equations. Scientists and engineers have to form a vivid picture within their heads that fires their imaginations and enables intuition to play a full role in the process of invention. It is to this end that transformation optics has been developed exploiting Faraday’s picture of electric and magnetic fields as lines of force which can be manipulated by the electrical permittivity and magnetic permeability of surrounding materials. TO says what has to be done to place the lines of force where we want them to be.

 

His latest research applies TO to the study of surface plasmons. The surfaces of metals such as gold and silver support density oscillations of the electrons, much like waves on a sea. These can couple to external radiation, but have a much shorter wavelength. The plasmonic excitations are greatly influenced by the shape of the surface and in particular by any singularities such as sharp corners, touching surfaces, or other rough features, which tend to attract very high field intensities: they act as harvesting points for any incident radiation. By applying transformations to simple structures, such as plasmonic waveguides consisting of two parallel sheets of silver, many of the singular structures can be generated through a singular transformation and their spectra understood through the spectrum of the original simple waveguide. Thus apparently diverse structures such as sharp edges, points, nearly touching spheres, can be shown to have a common origin and can in many cases be treated analytically. This deep understanding enables further properties of these structures to be elucidated such as the dispersion forces acting at short range between surfaces that are otherwise out of physical contact.