Condensed Matter Physics Seminar

Friday, February 19, 1999, 2 p.m.
Plant Sciences Building, Room 1130

Dirac fermions, gauge fields, and the mixed-state electronic structure of high-Tc cuprates

Marcel Franz

(Department of Physics & Astronomy, Johns Hopkins University)

Abstract:  In conventional s-wave superconductors the electronic excitations are gapped and the physics at low temperatures is dominated entirely by the collective response of the U(1) order parameter. High-Tc cuprates, on the other hand, exhibit low-energy fermionic excitations originating from the vicinity of the nodes in the d-wave gap, best described as massless Dirac fermions.  When external magnetic field is applied, both the Dirac fermions and the U(1) collective mode respond in a highly non-trivial manner, forming a vortex lattice with spontaneously broken translational symmetry.  Understanding the physics of a d-wave superconductor in the mixed state poses an entirely new theoretical challenge which is at the same time of great practical interest. I shall review the recent progress in this field with the particular emphasis on the theoretical results with broader implications and issues relevant to experiments. I will discuss the absence of quasiparticle bound states associated with the individual vortex cores, the anomalous transport properties of the mixed state, and the Landau level quantization at low fields.

Host: Sankar Das Sarma

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