Ongoing Research:

Colloquium on recent research in .ppt (recommended) and .pdf formats.

Current research interests include theory and phenomenology of high temperature superconductors and similar materials. Experiments show that such superconductors do not conform to the conventional BCS weak coupling paradigm, rooted in the Fermi liquid theory. Instead, it seems that the energy scale at which electrons form Cooper pairs far exceeds the one at which these pairs organize into the phase-coherent Bose condensate and the superconductivity itself sets in. Two distinct energy scales are suspected to originate from the proximity to the Mott insulating state of these materials. The Mott insulator results from strong short range (Hubbard) correlations in cuprates which impede the motion of electrons near half-filling of the conduction band. In the neighborhood of such an insulator, the fluctuations in the particle number N are greatly suppressed. This leads to enhanced quantum fluctuations in the phase φ of the Cooper pair wavefunction, via the quantum mechanical uncertainty relation ΔNΔφ ≥ 1 -- in turn, enhanced phase fluctuations inhibit Bose condensation. Between these two broadly separated energy scales, within the so-called "pseudogap state", the physics appears to be governed by the interactions of phase fluctuations and the low energy electrons "left over" in the wake of Cooper pairing (cuprate superconductors, being of a "d-wave" variety, always have some "leftover" electrons near the nodes of a d-wave gap function. The clickable figure to the right pays tribute to seminal experiments that established d-wave character of Cooper pairs).

At present, the emphasis of our research is on understanding such interactions between "leftover" electrons and quantum phase fluctuations of Cooper pairs and on the search for effective quantum field theories that describe them. The most important among the above interactions is the one between electrons and topological defects in phase φ, known as vortices and antivortices. This interaction contains a purely quantum mechanical component, the famed "Berry phase", which acts to frustrate the motion of "leftover" electrons through space filled with vortex-antivortex phase defects, and vice versa. The effective theories we explore typically include Dirac fermions ("leftover" electrons near the nodes) and quantum bosons (vortex-antivortex defects) as depicted in the figure to the left. Such theories routinely exploit concepts of duality, topological protection, and the like, and often possess unexpected symmetries -- exemplified by relativistic, gauge or chiral invariance -- once thought to be the exclusive domain of our elementary particle physics/superstring colleagues. These symmetries -- absent from the original problem -- are brought to life at low energies through correlated quantum motion of many particles and are aptly named emergent. They help guide and inspire theorists seeking elegance and beauty in an otherwise exceedingly complex world of condensed matter physics.

Prof. Tesanovic's research is supported in part by the National Science Foundation. Click here for some representative publications and selected recent presentations. A more pedagogical account of recent research activities is available in form of a colloquium (.ppt).