[MOS] April 28, 2015, Lord Lecture, Paul McEuen, Cornell University

[Zina M Queen]

24th Annual Richard C. Lord Lecture

Paul McEuen,

Cornell University

 

Light and Fast:

Probing carriers and vibrations

in 1D and 2D materials 

One and two dimensional materials are arguably the most interesting new materials systems to arise over the past two decades. First, electrons confined to a plane or a line have quantized energy levels and band structures that are quite different than their three-dimensional counterparts.  In addition their mechanical properties are dramatically modified, with transverse bending and thermal vibrational modes influencing basic materials properties in ways that are normally only seen in soft matter systems. But because of their diminutive size, these materials present particular challenges for measurement. As an example, a single nanotube or graphene sheet might only scatter 10-4 of the photons incident upon it, yet we wish to resolve information with nm spatial and ps temporal resolution. Here, we will discuss a number of unusual approaches to meet these challenges. First, we will discuss ultrafast photocurrent measurements that reveal the fundamental thermal relaxation processes for excited electrons. Next, we will discuss how circularly polarized light probes the “valley” polarization in a 2D semiconductor, leading to a Hall effect in the absence of a magnetic field. Finally, we will discuss experiments probing the static and dynamic physical fluctuations of graphene and carbon nanotubes using a combination of electronic and optical measurements, with implications for everything from nonlinear processes in nanoscale resonators to the fundamental bending stiffness of graphene.

 

Tuesday, April 28, 2015

12:00-1:00 p.m. 

Grier Room (34-401)

Refreshments served following the seminar

 

 

 

Sponsored by George R. Harrison Spectroscopy Laboratory,

and the Department of Chemistry,

Massachusetts Institute of Technology
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