Discovery of Dirac Node Arcs in PtSn4 (1603.00934v1)

Abstract: In topological quantum materials the conduction and valence bands are connected at points (Dirac/Weyl semimetals) or along lines (Line Node semimetals) in the momentum space. Numbers of studies demonstrated that several materials are indeed Dirac/Weyl semimetals. However, there is still no experimental confirmation of materials with line nodes, in which the Dirac nodes form closed loops in the momentum space. Here we report the discovery of a novel topological structure - Dirac node arcs - in the ultrahigh magnetoresistive material PtSn4 using laser-based angle-resolved photoemission spectroscopy (ARPES) data and density functional theory (DFT) calculations. Unlike the closed loops of line nodes, the Dirac node arc structure resembles the Dirac dispersion in graphene that is extended along one dimension in momentum space and confined by band gaps on either end. We propose that this reported Dirac node arc structure is a novel topological state that provides a novel platform for studying the exotic properties of Dirac Fermions.

• The paper identifies gapless Dirac node arcs in PtSn4 using laser-based ARPES and DFT, marking a breakthrough in topological quantum material research.
• It reveals both bulk and surface Dirac-like dispersions at critical Brillouin zone points, confirming the novel one-dimensional momentum extension of these states.
• The findings enhance our understanding of ultrahigh magnetoresistive properties and pave the way for innovative applications in quantum materials and advanced computing.

Discovery of Dirac Node Arcs in PtSn$_4$

The paper explores a nuanced exploration of Dirac node arcs within the ultrahigh magnetoresistive material PtSn$_4$ using advanced techniques like angle-resolved photoemission spectroscopy (ARPES) and density functional theory (DFT) calculations. The identification of these Dirac node arcs marks a significant advancement in our understanding of topological quantum materials, extending beyond the traditionally acknowledged Dirac/Weyl semimetals and line node semimetals.

Topological semimetals have captured significant interest due to their unique electronic properties and potential applications. While Dirac and Weyl semimetals have seen experimental confirmations, the paper highlights a gap in the confirmation of materials with line nodes. This paper introduces a distinct form, the Dirac node arc, which diverges from the conventional closed loops by presenting an extended dispersion in momentum space, constrained by band gaps at each end. These findings propose a novel topological state providing a platform for dirac fermion studies.

The experimental methodology focused on evaluating PtSn$_4$ using laser-based ARPES to examine the complex Fermi surface, particularly near the Z and X points of the Brillouin zone. The results revealed both bulk and surface components, suggesting that these features at the BZ edge carry potential topological character linked to the remarkable magnetoresistance properties of the material. Near the Z point, a linear Dirac-like band dispersion was observed, while at the X point, an intriguing arc structure formed by Dirac nodes was identified, differentiated by its one-dimensional extension in momentum space.

ARAPES data were corroborated by DFT calculations, enabling accurate mapping of both bulk and surface states in PtSn$_4$. These calculations confirmed the surface nature and unusual projections of Dirac nodes resulting in Dirac arcs. Importantly, the researchers demonstrated the gapless nature of Dirac-like dispersion, reinforcing the findings' topological significance by constructing a slab model that reduces the energy gap as layer numbers increase.

The research has potential implications in identifying materials with exceptional transport properties and expanding the catalog of topological quantum materials. By concentrating on PtSn$_4$'s magnetoresistance traits, and leveraging advanced tunable laser sources, the paper not only exemplifies a reverse approach to identifying topological states but also opens new vistas for exploration within condensed matter physics.

Future studies could advance these findings by experimentally confirming other materials hosting Dirac node arcs, fostering development in fields like quantum computing where such properties may be exploited. Integrating recent discoveries with theoretical frameworks will support the translation of these phenomena into applicable technology, potentially transforming material sciences.

This research broadens the scope of known nodal structures and encourages a deeper inspection into topological matter, underpinning the continued interest in quantum materials featuring complex topological characteristics.