Nanoscale Heat Transport
We use optical pump-probe techniques to explore heat transport over sub-micron length scales and at interfaces between dissimilar materials. The work aims to understand what guides energy transfer, particularly at metal-dielectric interfaces and in new nanoscale materials such as graphene, in order to guide the development of useful electronic devices that can withstand the heat dissipated while in operation. Currently we exploit Frequency-Domain Thermo-Reflectance (FDTR) and Time-Domain Thermo-Reflectance (TDTR), incorporating techniques such as frequency mixing or beam offsetting the pump and probe beams to explore quasi-ballistic and anisotropic heat transfer regimes.
Future data storage technologies aim to continue exploiting magnetic materials as storage medium. Whether for Heat-Assisted Magnetic Recording (HAMR), All-Optical magnetization Switching (AOS) or Magnetic Random Access Memories (MRAM), detailed knowledge of the dynamics of the magnetic spins is necessary to engineer useful data storage systems and predict how well they scale as the technology is advanced and bit size is reduced. The dynamic behavior of magnetic spins is well known at low temperatures down to picosecond time scales. However, as the electron temperature approaches the Curie point, the magnetization dynamics becomes richer, can't be described within the Landau-Lifshitz-Gilbert framework and longer-lived phenomena ensue. We explore the magnetization dynamics near these thermal limits with the aim of improving predictive models. To this end, our facilities allow us to study magnetic materials over variable heating/cooling time scales, and with arbitrary magnetic field orientation.
We frequently collaborate with the following groups: