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Tunable quantum phenomena in atomically thin crystals

Qiong Ma, MIT
Wednesday, January 16, 2019 - 3:30pm to 4:30pm
PAA 102

In quantum materials, the interplay of symmetry, topology, quantum geometry and interactions can lead to new electronic and optoelectronic responses. Two dimensional van der Waals materials feature highly tunable symmetry, band structure, carrier density and interactions. In this talk, I will discuss how we study new physics and realize new device functionalities by taking advantage of these exceptional tunabilities to achieve previously inaccessible experimental parameter regimes. First, I will show that the optoelectronic response of graphene can be controlled among distinct regimes by tuning the interaction dynamics of excited carriers. In particular, we observe a new type of photocurrent that appears exclusively in charge neutral graphene with unusual ultra-relativistic electron scattering kinematics. Second, I will show that the interplay between nontrivial topology and low crystalline symmetry in atomically thin WTe2 gives rise to new Berry curvature physics, which can be detected by nonlinear electrical transport and infrared photocurrent measurements. Remarkably, the nonlinear electrical transport in bilayer WTe2 uncovers a new type of electrical Hall effect in nonmagnetic materials and without external magnetic field. Our works also demonstrate new schemes for sensing and energy harvesting via harnessing intrinsic quantum properties.

Watch a video of the talk here.

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