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March 25, 20224:00 pm – 5:00 pm (CDT)

Symmetry-enabled topological excitations in 2D materials


Hanyu Zhu (Rice University)


Ar. Abanov



Mitchell Institute for Fundamental Physics & Astronomy

College Station, Texas 77843

Event Details

The strong coupling between electron, lattice, and spin degrees of freedom in two-dimensional (2D) systems, especially van der Waals materials in the monolayer limit, leads to unique light-matter interaction properties. The symmetry of the 2D lattices plays an important role in many such properties. For example, the 2D honeycomb lattice leads to chiral Dirac fermions in graphene’s electronic band structure, providing constant optical absorption in a wide frequency range and the valley-pseudospin correspondence. The topological nature of these charge states is also applicable to the phonons and magnons in diverse 2D van der Waals materials. In this talk, I will first show optical control of the excitonic valley and spin in 2D honeycomb semiconductors with inversion symmetry breaking, and then use the excitonic states to probe the chiral valley phonons, which are expected to have longer quantum coherence. After that, I will introduce the experimental discovery of coherent coupling, or quantum cooperativity, between phonons and magnons in 2D antiferromagnets, whose non-trivial topology is protected by mirror symmetry and tunable by field-broken time reversal symmetry. Together, these phenomena demonstrate the great potential of 2D materials for ultrafast quantum control.

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