# Condensed Matter Seminars

**Condensed Matter**

Thursday, December 5, 2019

11:00 AM

Physics Building, Room 313

Note special time.

Note special room.

## "Monopole Superconductivity and Density-Wave Order in Weyl Semi-metals"

**Professor Yi Li , Johns Hopkins University**

[Host: Dima Pesin]

Although the existence of magnetic monopoles is admitted by the fundamental laws, the real monopoles in nature remain elusive. Nevertheless, variations of monopoles appear in realistic condensed matter systems, from quantum Hall effects to topological superconductivity, which spur a race to discover new exotic topological phases of matter. In this talk, we will present a dramatic effect arising from topological Fermi surfaces -- a novel topological class of superconductivity and density-wave orders: When the ordered pairs acquire non-trivial two-particle Berry phases, their pairing phases cannot be globally well-defined in the momentum space. Therefore, the conventional description of superconducting pairing symmetries in terms of spherical harmonics (e.g. s-, p-, d-waves) ceases to apply. Instead, they are characterized by topologically protected nodal gap functions represented by monopole harmonic functions. This so-called “monopole harmonic order” is expected to be realized and detected in Weyl semimetal materials.

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