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Valley skyrmion in graphene visualized by a scanning tunneling microscope.
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Magic-angle graphene is an incredible multi-functional material, easily tuned amongst a diverse set of quantum phases by changing its temperature, magnetic field, and electronic density. Here, researchers have uncovered essential signatures of its unconventional superconducting phase (yellow), which conducts electricity with zero resistance and zero energy loss, and its previously unknown pseudogap regime (blue), a seemingly necessary precursor to superconductivity.
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Two graphene sheets stacked on each other with a twist make a long-wavelength moiré pattern.
Harnessing the power of quantum microscopy techniques
A goal at the forefront of condensed matter physics is understanding how quantum phases of matter emerge from interactions among electrons or from topological properties of electronic states. These quantum phases can have novel electronic properties and host unusual quasiparticles, the control and manipulation of which may lead to new quantum technologies.
Our group's focus is to harness the power of high-resolution scanning quantum microscopy techniques to understand such novel phases of matter. These studies have provided information that is impossible to obtain using conventional macroscopic averaging techniques typically used in condensed matter physics. For example, scanning tunneling microscopy (STM) techniques can directly visualize electronic wavefunctions in quantum materials, allowing us to understand the nature of new quantum phases and their excitations.
Our group not only applies well established techniques of quantum microscopy across a wide range of material platforms, but we also develop new microscopy methods and tools.
Recent Highlight
Visualizing broken symmetry and topological defects in a quantum Hall ferromagnet
The interaction between electrons in graphene under high magnetic fields drives the formation of a rich set of quantum Hall ferromagnetic phases (QHFM), with broken spin or valley symmetry. Visualizing atomic scale electronic wavefunctions with scanning tunneling spectroscopy (STS), we resolve microscopic signatures of valley ordering in QHFM and spectral features of fractional quantum Hall phases of graphene. As reported in Science (December 2021): Read more.
