Using Disorder to Detect Local Order: Noise and Nonequilibrium Effects of Stripes in the Presence of Quenched Disorder

Purdue University, West Lafayette IN

Investigators

Abstract

TECHNICAL SUMMARY: This award supports theoretical research and education on strongly correlated electron materials with a focus on spontaneous electronic pattern formation at the nanoscale. The PI will develop new ways of studying materials, explicitly including disorder, and using noise, nonequilibrium effects, and mesoscopic geometries in order to elucidate the local electronic patterns. For example, stripes (like other proposed real space orders) may be important for high temperature superconductivity, but they have only been observed in a subset of cuprate superconductors, most notably in cases where the stripes exhibit true long-range order. However, even disordered or slowly fluctuating stripes (invisible to many standard bulk probes) are sufficient for a stripes-based mechanism of high temperature superconductivity. The PI recently mapped the problem of disordered stripes to the random field Ising model. The PI will use simulations on this model to make predictions about how to detect disordered stripes using noise and nonequilibrium effects in, e.g., transport, STM, neutron scattering, and magnetic hysteresis. This award also supports the PI?s efforts to continue to develop the mentoring program she began for graduate women in the physics program at her home institution, by initiating a program to invite graduate physics alumnae back to campus to discuss career options with current graduate and undergraduate students in physics. The PI will also continue to visit local high schools to discuss her research. This outreach combines interactive hands-on superconductivity demonstrations with education about contemporary condensed matter research. In addition, the proposed work will advance the training of one graduate student and two postdoctoral associates. NON-TECHNICAL SUMMARY: This award supports theoretical research and education aimed at understanding fundamental questions raised in the study of high temperature superconductors. These are materials that can transport electric current without loss at sufficiently low temperatures. The physical mechanism by which electrons enter this cooperative quantum mechanical state of superconductivity remains a subject of intense research for the high temperature superconductors. These materials exhibit superconductivity at much higher temperatures, but still well below room temperature, than the much better understood superconducting materials that one might encounter in a medical magnetic resonance imaging machine. Understanding the mechanism for superconductivity may lead to the discovery or engineering of materials that exhibit superconductivity at still higher temperatures, with the possibility of enabling economical new technologies for power transmission and new electronic devices. The research will focus on an interesting aspect of the puzzle, the spatially varying patterns of characteristic quantum mechanical properties of electrons that have been observed in experiments on some high temperature superconductors. This award also supports the PI?s efforts to continue to develop the mentoring program she began for graduate women in the physics program at her home institution, by initiating a program to invite graduate physics alumnae back to campus to discuss career options with current graduate and undergraduate students in physics. The PI will also continue to visit local high schools to discuss her research. This outreach combines interactive hands-on superconductivity demonstrations with education about contemporary condensed matter research. In addition, the proposed work will advance the training of one graduate student and two postdoctoral associates.