Spring 2018

In recent decades, a large scientific effort has focused on harnessing spin transport for providing insights into novel materials and low-dissipation information processing. We introduce single spin magnetometry based on nitrogen-vacancy (NV) centers in diamond as a new and generic platform to locally probe spin chemical potentials which essentially determine the flow of spin currents. We use this platform to investigate magnons in a magnetic insulator yttrium iron garnet (YIG) on a 100 nanometer length scale. We demonstrate that the local magnon chemical potential can...

The chiral spin textures are a consequence of the anti-symmetric exchange interaction, which presents in the material systems with broken inversion symmetry, such as B20FeGe. This interaction enables chiral magnetic order, including topologically non-trivial magnetic skyrmions, which display rich new magnetic phenomena and require low critical current densities to manipulate.  This makes magnetic skyrmions a promising platform for power-efficient spintronics applications. Therefore, a deeper understanding of the static and dynamic magnetic properties of these materials...

Berry phase played an important role in quantum mechanics and underlying the physics of a wide range of materials from topological phases of matters to various 2D materials. While the effect of Berry phase has been extensively studied and shown through quantized electron transport experiment, the geometric aspect of wavefunction— determined by Berry curvature has remained much less understood experimentally. In this talk, I will use bilayer graphene as a model system to demonstrate effects of Berry phase and Berry curvature on materials’ electronic and optical...

Superconducting qubits offer excellent prospects for manipulating quantum information, with good qubit lifetimes, high fidelity single- and two-qubit gates, and straightforward scalability (admittedly with multi-dimensional interconnect challenges). One interesting route for experimental development is the exploration of hybrid systems, i.e. coupling superconducting qubits to other systems. I will report on our group's efforts to develop approaches that will allow interfacing superconducting qubits in a quantum-coherent fashion to mechanical resonators and to optomechanical devices. The...

Quantum materials are fascinating platforms where macroscopic quantum phenomena occur. As a prominent example, superconductors conduct electricity with no dissipation at low temperatures, holding great promise to address global energy challenges. It is of tremendous scientific and technological interest to enhance superconducting transition temperatures. In this talk I will elucidate the principles of interfacial engineering and co-operative interactions through studies of bulk superconductors, and demonstrate how I implement these concepts in fabricating an iron selenide/strontium...