Mind the gap: quantum effects and optical-frequency magnetism in plasmonic particle junctions

Thursday, March 12, 2015 -
4:00pm to 5:00pm
Jennifer Dionne
Speaker's Institution: 
Materials Science and Engineering, Stanford University


Electrons and photons can coexist as a single entity called a surface plasmon—an elementary excitation found at the interface between a conductor and an insulator. Plasmons are evident in the vivid hues of rose windows, which derive their color from small metallic nanoparticles embedded in the glass. They also provide the basis for color-changing biosensors, photo-thermal cancer treatments, improved photovoltaic cell efficiencies, and nano-optical tweezers. While most applications have relied on classical plasmonic effects, quantum phenomena can also strongly influence the plasmonic properties of nanometer-scale systems. In this presentation, I’ll describe my group’s efforts to probe plasmon modes spanning both classical and quantum domains. We first explore the optical resonances of individual metallic nanoparticles as they transition from a classical to a quantum-influenced regime. We then use these results to monitor heterogeneous catalytic reactions on individual nanoparticles. Subsequently, using real-time manipulation of plasmonic particles, we investigate plasmonic coupling between pairs of particles separated by nanometer- and Angstrom-scale gaps. For sufficiently small separations, we observe the effects of classical coupling and quantum tunneling between metallic particles on their plasmon resonances. By utilizing these effects, we demonstrate the colloidal synthesis of an isotropic metafluid or "metamaterial paint" that exhibits a strong magnetic response – and the potential for negative refractive indices – at visible frequencies. Finally, we introduce a new technique, cathodoluminescence tomography, that enables three-dimensional visualization of light-matter interactions with nanoscale spatial and spectral resolution.




Jennifer Dionne is an assistant professor in the department of Materials Science and Engineering at Stanford University. Jen received B.S. degrees in Physics and Electrical & Systems Engineering from Washington University in St. Louis in 2003, and a Ph.D. degree in Applied Physics from the California Institute of Technology in 2009, under the supervision of Prof. Harry Atwater. She joined Stanford in 2010 following a postdoctoral research fellowship at the University of CA, Berkeley and Lawrence Berkeley National Laboratory, working with Prof. Paul Alivisatos. Jen’s research develops new optical materials for applications ranging from high-efficiency solar energy conversion to bioimaging and manipulation. This research has led to demonstration of negative refraction at visible wavelengths, development of a subwavelength silicon electro-optic modulator, development of quantum plasmonic materials, design of new optical tweezers for nano-specimen trapping, and demonstration of a metamaterial fluid. Her work has been recognized with a Sloan Fellowship (2015), the Presidential Early Career Award for Scientists and Engineers (2014), and the inaugural Kavli Nanoscience Early Career Lectureship from MRS (2013). Further, she has received an NSF CAREER Award (2012), AFOSR Young Investigator Award (2011), Outstanding Young Alum award from Washington University in St. Louis (2012), and was selected as one of Technology Review's TR35 (2011).