Electronic Evidence of Temperature-Induced Lifshitz Transition and Topological Nature in ZrTe5 (1602.03576v1)

Abstract: The topological materials have attracted much attention recently. While three-dimensional topological insulators are becoming abundant, two-dimensional topological insulators remain rare, particularly in natural materials. ZrTe5 has host a long-standing puzzle on its anomalous transport properties; its underlying origin remains elusive. Lately, ZrTe5 has ignited renewed interest because it is predicted that single-layer ZrTe5 is a two-dimensional topological insulator and there is possibly a topological phase transition in bulk ZrTe5. However, the topological nature of ZrTe5 is under debate as some experiments point to its being a three-dimensional or quasi-two-dimensional Dirac semimetal. Here we report high-resolution laser-based angle-resolved photoemission measurements on ZrTe5. The electronic property of ZrTe5 is dominated by two branches of nearly-linear-dispersion bands at the Brillouin zone center. These two bands are separated by an energy gap that decreases with decreasing temperature but persists down to the lowest temperature we measured (~2 K). The overall electronic structure exhibits a dramatic temperature dependence; it evolves from a p-type semimetal with a hole-like Fermi pocket at high temperature, to a semiconductor around ~135 K where its resistivity exhibits a peak, to an n-type semimetal with an electron-like Fermi pocket at low temperature. These results indicate a clear electronic evidence of the temperature-induced Lifshitz transition in ZrTe5. They provide a natural understanding on the underlying origin of the resistivity anomaly at ~135 K and its associated reversal of the charge carrier type. Our observations also provide key information on deciphering the topological nature of ZrTe5 and possible temperature-induced topological phase transition.

• The paper reveals a temperature-induced Lifshitz transition in ZrTe5, linking dramatic band shifts to resistivity anomalies and carrier sign reversals.
• It employs high-resolution laser-based ARPES to map the evolution of electronic states from a p-type semimetal to an n-type semimetal across temperature changes.
• The study uncovers emergent surface states that hint at topological edge features, suggesting potential applications in spintronic devices.

Electronic Evidence of Temperature-Induced Lifshitz Transition and Topological Nature in ZrTe$_5$

The paper presented investigates the electronic properties of ZrTe$_5$, a material of significant interest due to its anomalous transport properties and potential as a topological insulator. The paper provides a comprehensive analysis of the temperature-dependent electronic structure of ZrTe$_5$, employing high-resolution laser-based angle-resolved photoemission spectroscopy (ARPES). This research elucidates the occurrence of a temperature-induced Lifshitz transition, a shift in the electronic structure topology, which is pivotal to understanding the resistivity anomaly and topological characteristics of the material.

The investigation reveals two primary bands with nearly linear dispersion near the Fermi level at the Brillouin zone center: a conduction band (upper branch, UB) and a valence band (lower branch, LB), with an energy gap that narrows with decreasing temperature but persists to low temperatures, around 2 K. The paper meticulously documents dramatic temperature-dependent shifts in these bands. Above 135 K, ZrTe$_5$ behaves as a p-type semimetal characterized by a hole-like Fermi surface. As the temperature decreases to approximately 135 K, the material transitions to a semiconductor state before becoming an n-type semimetal at even lower temperatures, marked by an electron-like Fermi surface. This transition aligns closely with resistivity peaks observed experimentally and accounts for Hall coefficient and thermopower sign reversals, previously unexplained anomalies which the paper suggests are manifestations of the Lifshitz transition.

Additional ARPES data demonstrate the emergence of new electronic states on the surface, potentially linked to edge states signaling the topologically non-trivial nature of ZrTe$_5$. While it remains debatable whether ZrTe$_5$ is a strong or weak topological insulator, the observed persistence of an energy gap across the temperature spectrum challenges the interpretation of ZrTe$_5$ as a three-dimensional Dirac semimetal. The paper proposes that further investigations are required, especially to discern whether high pressure or chemical modification might induce a topological phase transition, solidifying ZrTe$_5$'s status as a strong topological insulator.

The findings have theoretical implications for the electronic and topological transitions in materials with similar layered structures. The practical implication involves potential applications in spintronic devices, where materials with tunable topological properties are invaluable. Future research directions should focus on exploring ways to experimentally confirm the presence of edge states, investigating the interaction between interlayer coupling and topological properties, and examining other transition metal pentatellurides for similar behaviors. Understanding the temperature-induced band shifts without external doping remains an open question with vast potential to reveal novel quantum behaviors in topological materials. This paper lays a foundational understanding of ZrTe$_5$, guiding future explorations in advanced material properties and applications.