NovelZ2Topological Metals and Semimetals

Nodal-link semimetals

Topological phases of matter have been among the most active research subjects in condensed matter physics. They can be broadly classified as two major classes. The first class of phases, including topological insulators and superconductors[1–6], and other symmetry protected topological phases[7], have gapped bulks with nontrivial topological structures characterized by topological invariants[8...

Helicons in Weyl semimetals

Photocurrents in Weyl semimetals

Ching-Kit Chan,1 Netanel H. Lindner,2 Gil Refael,3 and Patrick A. Lee1 1Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA 2Physics Department, Technion, 320003 Haifa, Israel 3Institute of Quantum Information and Matter and Department of Physics, California Institute of Technology, Pasadena, California 91125, USA (Received 13 August 2016; revised m...

Topological Semimetals carrying Arbitrary Hopf Numbers: Hopf-Link, Solomon’s-Knot, Trefoil-Knot and Other Semimetals

We propose a new type of Hopf semimetals indexed by a pair of numbers (p, q), where the Hopf number is given by pq. The Fermi surface is given by the preimage of the Hopf map, which consists of loops nontrivially linked for a nonzero Hopf number. The Fermi surface forms a torus link, whose examples are the Hopf link indexed by (1, 1), the Solomon’s knot (2, 1), the double Hopf-link (2, 2) and t...

Emergent Spacetime Supersymmetry in 3D Weyl Semimetals and 2D Dirac Semimetals.

Supersymmetry (SUSY) interchanges bosons and fermions but no direct evidence of it has been revealed in nature yet. In this Letter, we observe that fluctuating pair density waves (PDW) consist of two complex order parameters which can be superpartners of the unavoidably doubled Weyl fermions in three-dimensional lattice models. We construct explicit fermionic lattice models featuring 3D Weyl fe...