Triple Point Topological Metals (1605.04653v2)

Abstract: Topologically protected fermionic quasiparticles appear in metals, where band degeneracies occur at the Fermi level, dictated by the band structure topology. While in some metals these quasiparticles are direct analogues of elementary fermionic particles of the relativistic quantum field theory, other metals can have symmetries that give rise to quasiparticles, fundamentally different from those known in high-energy physics. Here we report on a new type of topological quasiparticles -- triple point fermions -- realized in metals with symmorphic crystal structure, which host crossings of three bands in the vicinity of the Fermi level protected by point group symmetries. We find two topologically different types of triple point fermions, both distinct from any other topological quasiparticles reported to date. We provide examples of existing materials that host triple point fermions of both types, and discuss a variety of physical phenomena associated with these quasiparticles, such as the occurrence of topological surface Fermi arcs, transport anomalies and topological Lifshitz transitions.

• The paper introduces a novel classification of triple point fermions, identifying two distinct types based on unique band crossing behaviors in symmorphic metals.
• It utilizes numerical analysis to reveal quantized Berry phases, nodal lines, and Fermi arcs as clear experimental signatures.
• The study predicts new transport phenomena from doping-driven Lifshitz transitions, offering actionable insights for advancements in quantum materials.

Analysis of "Triple Point Topological Metals"

The paper of topological quasiparticles within condensed matter physics has enriched understanding across both theoretical and practical domains. The paper "Triple Point Topological Metals" expands on this knowledge by proposing a new class of topological fermionic quasiparticles realized in metals with symmorphic crystal structures—referred to as triple point fermions. This research investigates the conditions and implications of such quasiparticles, emphasizing the topological distinction of these quasiparticles upon the broader map of known topological excitations.

Summary of Contributions

The paper identifies two topologically distinct types of triple point fermions, each characterized by their unique band crossing behavior in momentum space protected by point group symmetries. This classification enriches the taxonomy of topological quasiparticles by delineating new entities protected by symmetries previously unexplored in this context. The authors provide concrete examples of materials that can host these quasiparticles, specifically highlighting the ZrTe family and CuPt-ordered InAs$_{0.5}$Sb$_{0.5}$.

Numerical Results and Predictions

The numerical work underscores significant topological behaviors, such as the presence of nodal lines with quantized Berry phases and Fermi arcs on surfaces, which are vital for experimental validation. Strikingly, the paper predicts that type-A triple point fermions manifest novel transport phenomena due to their effects on the Landau level spectrum under the application of magnetic fields. The presence of doping-driven topological Lifshitz transitions presents a dynamic tunability of these materials, potentially enabling new electronic properties guided by topological phase changes.

Implications for Condensed Matter Physics

This research opens pathways for further material discoveries, accommodating topological phases unaddressed in the prior literature. By providing explicit space group conditions for the emergence of triple point quasiparticles, the paper stands as a guide for experimental endeavors aiming to synthesize and explore these predicted phases. Moreover, the implications spill over into the realms of quantum computing and electronic engineering, where topologically robust states may serve as a new frontier for devices requiring stability against perturbations.

Future Prospects

Looking ahead, the richness of physics surrounding triple point fermions is anticipated to drive advancements in understanding complex interactions within topological systems. Speculative extensions of this work could consider the effects of breaking specific protecting symmetries, revealing potentially novel transitions to other topological phases such as Weyl and Dirac semimetals. Furthermore, the interactions of these triple point fermions with external perturbations, including electromagnetic and optical fields, may disclose uncharted phenomena at the intersection of quantum mechanics and material science.

In summary, this paper provides a comprehensive theoretical framework for triple point fermions, opening up new dimensions in the paper of quantum materials. By setting a clear path toward experimental realizations, it pushes the boundary of current understanding in topological matter and invites a wealth of investigative opportunities in the field.