Research

Introduction


      All my research involves imaging systems in unique ways. Specifically I have spent the last decade or so working with scanning probe microscopes (SPM), which allow the measure of atomic scale to micro scale systems by locally probing their properties. This allows a detailed image of the force, density of states, or magnetic properties to be obtained. Over the course of my career I have worked with two specific SPM techniques.

 

Scanning Tunneling Microscopy on Cuprates

      The first, spectroscopic imaging scanning tunneling microscopy (SI-STM), measures local density of states (LDOS) of atomically flat and clean surfaces. This allows the localized and delocalized electronics states to be probed and provides insight into the phenomena that are present. By scanning larger areas, electronic oscillations can be measured that contain information about the scattering of electrons and band structure of the material. Good SI-STM data is hard to come by. The instrument must be cooled, rigidly designed and have extremely low noise in order to take intrinsically limited data that is not artificially broadened. Measuring the electronic oscillations in cuprates is even harder and the measurement of it can be used as one of the penultimate tests of the instruments capabilities.

Publications:

k-space Origins of Scattering in Bi2Sr2CaCu2O8+x” Jacob W. Alldredge, Eduardo M. Calleja, Jixia Dai, H. Eisaki, S. Uchida, Kyle McElroy, Submitted PRB, Con Mat/1302.5670

Universal Disorder in Bi2Sr2CaCu2O8+x” J. W. Alldredge, K. Fujita, H. Eisaki, S. Uchida, and Kyle McElroy, Phys. Rev. B 87, 104520 (2013), Con Mat/1210.3002

“Three-component electronic structure of the cuprates derived from spectroscopic-imaging scanning tunneling microscopy” J. W. Alldredge, K. Fujita, H. Eisaki, S. Uchida, and Kyle McElroy, PRB 85, 174501 (2012)

“Evolution of the electronic excitation spectrum with strongly diminishing hole-density in superconducting Bi2Sr2CaCu2O8+δ” J.W. Alldredge, Jinho Lee, K. McElroy, M. Wang, K. Fujita, Y. Kohsaka, C. Taylor, H. Eisaki, S. Uchida, P.J. Hirschfeld and J.C. Davis, Nature Physics Nature Physics, 4, 319 (2008).

 

Magnetic Particle Force Microscopy Applications and Development

      The 2nd technique is magnetic particle force microscopy (MPFM). MPFM is a much larger scale, room temperature technique that was designed to measure the magnetic properties of large micron scale particles. This technique relies on a unique magnetic field configuration, a force measurement, and computational modeling to determine the m-H curve of a particle. One possible application for MPFM is the fingerprinting of soil samples for erosion measurements. Unlike SI-STM, the MPFM has many real world applications and the design lends itself to being simplified allowing a robust instrument to be created that can possibly be deployed to the field.

Publications:

PML newsletter "MRI: Contrast Agents of Change" March 5, 2013

 “Magnetic Particle Imaging with a Cantilever Detector” JW. Alldredge, John Moreland, Journal of Applied Physics 112, 023905 (2012)

NIST PostDoc Symposium Poster 2012