CAREER: Broadband Microwave and THz Investigations of Correlated Electron and Nanostructure Systems

Johns Hopkins University, Baltimore MD

Investigators

Abstract

TECHNICAL ABSTRACT The response of condensed matter to electromagnetic radiation is a fundamental probe of its electronic structure. Correlated systems and their nanostructures like quantum magnets, high-Tc superconductors, 2D electron gasses, graphene and others exhibit a multitude of novel properties as a result of strong electron-electron interactions, reduced dimensionality, and interfacial effects. Unfortunately, many of their natural time scales lie in the GHz and THz region of the electromagnetic spectrum that has been difficult to access in a broadband manner. The upper part of this range has even become known as the `Terahertz Gap', which is a range of frequencies (roughly 0.05 to 10 THz) and energy scales above what is easily accessible with radio-frequency and microwave electronics, but below that accessible easily with conventional optics. Recently, however, there have been a series of dramatic breakthroughs in broadband microwave GHz range and time-domain THz spectroscopy that allow measurements which were simply not possible previously. This proposal for research at The Johns Hopkins University is aimed at the exploitation of these recent dramatic advances in GHz and THz range spectroscopic techniques for the investigation of exotic electronic states of matter at low temperatures. The systems to be investigated include novel dielectrics, electronic glasses, nanostructures such as interfacial metal heterostructures and graphene, and materials in proximity to quantum (T=0) phase transitions. These systems are of central importance for intellectual issues at the forefront of condensed matter physics and their exploration in the GHz and THz spectral range offers great scientific opportunity. The proposed work is of particular educational value to students owing to the material science and low frequency electrodynamics techniques that will be employed and which are finding broad application in research and private industry. In this regards, specific teaching laboratories will be developed. Public outreach activities in the form of the Johns Hopkins Physics Fair will also be realized. NON-TECHNICAL ABSTRACT: It is hardly an exaggeration that most of what we know about physical systems comes from their response to perturbations at their characteristic frequencies. For instance, the fundamental tone of a plucked violin string depends on the length of the string, the tension in it, and its thickness. This is true from the acoustics of a violin to the energies of atoms. Unfortunately the natural frequency scales of many solid materials fall in a range which has been prohibitively difficult to access technically until recently. This project takes advantage of recent dramatic technical advances in THz and microwave spectroscopy to characterize the natural frequency scales of solids. Material systems like superconductors, which can conduct electricity without resistance and various magnetic states will be studied. The investigations performed herein will give absolutely essential information to develop new materials with important technological implications. These technological developments are coupled to a broad initiative in education and outreach. The proposed work is of particular educational value to students owing to the material science and low frequency electrodynamics techniques that will be employed and which are finding broad application in research and private industry. Specific teaching laboratories will be developed. Public outreach activities in the form of the Johns Hopkins Physics Fair will also be realized.