Electronic liquid crystal correlations in the pseudogap phase of high Tc cuprates – Michael Lawler

Date: Thu. October 13th, 2011, 4:15 pm-5:15 pm
Location: Rockefeller 301

The pseudogap phase of cuprate oxides is one of the most perplexing phases in condensed matter physics; it is a poor metal that, at lower temperatures, becomes one of the best superconductors. Recently [1], the peculiarities of the pseudogap phase were beautifully captured by STM data on Bi₂Sr₂CaCu₂O_8+x in the form of an inhomogenious spatial pattern of density of states. From these pseudogap patterns, we construct liquid crystalline order parameter fields to quantify the symmetry breaking features [2,3]. These fields reveal two properties of the pseudo gap phase. It has a net anisotropy (nematic ordered) over at least 100 nm length scales and the anisotropy is locally disturbed by imperfections in another element of the pseudo gap pattern: a stripe-like (smectic ordered) pattern. These two properties are nicely captured by a minimal symmetry allowed free energy of the smectic and nematic order parameters fields. Our results therefore provide a basis for a theory of the pseudogap phase as well as pave the way for a test of the importance of these electronic liquid crystalline properties in the mechanism of high temperature superconductivity.

[1] Khosaka et. al., Science 315, 1380 (2007)
[2] Lawler, Fujita et. al., Nature 466, 347 (2010)
[3] Mesaros, A. et. al., Science 333, 436 (2011)