The Hoffman Lab uses high resolution scanning probe techniques to understand and control the electronic and magnetic properties of exotic materials such as copper and iron-based high-T_c superconductors, topological materials, and vanadium oxides. Scanning tunneling microscopy was conceived as a powerful tool for real-space imaging of electron states with atomic resolution. We have developed new analysis techniques by which STM can achieve picoscale resolution in real space, and can also probe the momentum-space structure of the electrons via quasiparticle interference imaging. This simultaneous real-space and momentum-space information is a crucial advance towards understanding materials with nanoscale electronic inhomogeneity, which may arise spontaneously from chemical doping or strong correlations, or intentionally from device fabrication. We have taken the first steps to extend this electronic imaging capability to obtain spin information, using antiferromagnetic chromium STM tips to image La_1.4Sr_1.6Mn₂O₇

In addition to passive imaging, the Hoffman Lab is working on several techniques to actively manipulate the electronic phases of materials at the nanoscale. For example, we have used force microscopy to locally induce the metal-insulator transition in VO₂, and to controllably reposition individual magnetic vortices in the high-T_c superconductor NdFeAsO_1-xF_x.

The Hoffman Lab is also working towards the growth of novel films and interfaces using molecular beam epitaxy - a technique which allows the controlled deposition of a single atomic layer at a time. We have grown a single layer of FeSe on SrTiO₃, which superconducts above 100K, at 10x higher temperature than the bulk T_c. MBE and STM capabilities will be combined and enhanced, for atomic precision control and understanding of diverse materials.