Seminar

Surface plasmons (SPs) are evanescent waves generated through the collective oscillations of electrons at a metal/dielectric interface under optical excitation. Due to the strong light-electron coupling and near-field nature, surface plasmons offer: (1) the opportunity for sub-wavelength spatial confinement of optical waves is enabled; and (2) giant local field enhancement of optical waves is permitted. These unique attributes lead to the long-envisaged optical circuits, and allowed breakthroughs in the generally termed “plasmonics” [1]. For example, in the realizations of optical nano-...

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...

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...

Over the last several years, research in the field of cavity optomechanics has developed extraordinarily sensitive and low loss devices as well as clever measurement techniques to probe macroscopic mechanical systems in the quantum regime.  If one observes carefully, the noise in optically detected mechanical resonators can reveal a remarkable tale of the fundamental quantum mechanics of measurement embodied by Heisenberg’s microscope type physics.  In this talk, I will review the basic consequences of quantum measurement backaction in the context of recent cavity optomechanics experiments...