insight - Scientific Computing - # Landau Level Spectroscopy of LaTe3

Landau Level Spectroscopy Reveals Electron-Hole Fermi Pockets and Electron-Boson Coupling in the Charge Density Wave Semimetal LaTe3

Q: How does the electron-boson coupling strength vary across different members of the RTe3 family, and how does this variation correlate with the emergence of different electronic phases?

The strength of electron-boson coupling in RTe3 compounds is expected to be influenced by the specific rare-earth element (R) present. Here's a breakdown of how this coupling might vary and its implications: Heavier R elements: Compounds with heavier R elements (like Ce, Tb, Dy) tend to exhibit stronger electron-phonon coupling. This is linked to the larger ionic radii of these elements, leading to a stronger influence on the Te-Te bonding within the Te square net. Stronger electron-phonon coupling can enhance the tendency towards charge density wave (CDW) instabilities, as observed in these materials. Additionally, the presence of 4f electrons in these heavier R elements introduces a new degree of freedom. The interaction between these localized 4f electrons and the conducting electrons in the Te layers can lead to Kondo effects, heavy fermion behavior, and complex magnetic ordering, further enriching the electronic phase diagram. Lighter R elements: In contrast, LaTe3, with the lighter La atom, exhibits weaker electron-phonon coupling. This is reflected in the smaller coupling constant (λ = 0.19) determined from the Landau level spectroscopy. The weaker coupling in LaTe3 makes it less susceptible to CDW formation at low temperatures, and indeed, only the high-temperature CDW1 phase is observed. Correlation with Electronic Phases: The variation in electron-boson coupling strength directly correlates with the emergence of different electronic phases in the RTe3 family. Stronger coupling favors CDW formation and can even influence the CDW transition temperatures. For example, the heavier RTe3 compounds often exhibit multiple CDW transitions, while LaTe3 only shows one. Moreover, the interplay between electron-phonon coupling and the interaction between 4f and conduction electrons can give rise to exotic ground states like unconventional superconductivity and complex magnetic ordering, as observed in some RTe3 materials.

Q: Could the observed electron-hole Fermi pockets in LaTe3 be manipulated or tuned through external stimuli such as pressure or doping to induce more exotic electronic ground states?

Yes, the observed electron-hole Fermi pockets in LaTe3 present a promising platform for manipulation via external stimuli like pressure and doping, potentially leading to the emergence of exotic electronic ground states. Here's why: Pressure: Applying pressure can modify the lattice constants and, consequently, the electronic band structure of LaTe3. This can lead to: Fermi surface nesting: Pressure could tune the electron and hole Fermi pockets to perfectly nest, enhancing the interaction between electrons and holes. This nesting condition is often a key ingredient for the formation of excitonic insulators or unconventional density wave states. Enhanced electron-phonon coupling: Pressure can also enhance the electron-phonon coupling strength, potentially pushing LaTe3 towards a regime where multiple CDW transitions or even unconventional superconductivity might emerge. Doping: Introducing dopants into LaTe3 can alter the carrier concentration and influence the electronic correlations, leading to: Lifted Fermi surface degeneracy: Doping can lift the degeneracy between the electron and hole pockets, potentially favoring the formation of more exotic ground states. Modified electronic interactions: Doping can introduce disorder or modify the screening of Coulomb interactions, potentially tipping the balance towards different electronic instabilities. Examples in RTe3 Family: The potential for inducing exotic states through pressure and doping is supported by observations in other RTe3 compounds. For instance, pressure-induced superconductivity has been reported in TbTe3, highlighting the sensitivity of these materials to external stimuli.

Q: What are the potential implications of the observed electron-boson coupling in LaTe3 for the development of novel quantum materials with enhanced superconducting or topological properties?

The observed electron-boson coupling in LaTe3, while weak, holds intriguing implications for the development of novel quantum materials, particularly in the context of superconductivity and topological phases: Unconventional Superconductivity: Even though LaTe3 itself is not superconducting, the presence of electron-boson coupling, as evidenced by the Landau level spectroscopy, suggests that related compounds with stronger coupling could host unconventional superconductivity. This is particularly relevant considering the close relationship between LaTe3 and other RTe3 members where pressure-induced superconductivity has been observed. By understanding the interplay between electron-boson coupling, Fermi surface topology, and magnetic interactions in these materials, researchers could potentially design new RTe3-based superconductors with higher critical temperatures or novel pairing mechanisms. Topological Materials: The electron-hole Fermi pockets in LaTe3, combined with the possibility of tuning the band structure through pressure or doping, open avenues for exploring topological phases. For instance, by manipulating the Fermi level and inducing band inversions, it might be possible to drive LaTe3 into a topological insulator or a Dirac semimetal phase. The presence of electron-boson coupling could further enrich the topological properties of these phases, potentially leading to the discovery of novel topological superconducting states. Quantum Material Design: More broadly, the insights gained from studying electron-boson coupling in LaTe3 contribute to a deeper understanding of how electronic correlations and interactions can give rise to exotic phases in quantum materials. This knowledge is crucial for the rational design of new materials with tailored properties, paving the way for advancements in areas such as quantum computing, spintronics, and energy applications.

Core Concepts

Using Landau level spectroscopy, researchers observed pronounced electron-hole Fermi pockets and evidence of electron-boson coupling in LaTe3, a charge density wave semimetal, providing insights into the electronic behavior of this material and the broader RTe3 family.

Abstract

Bibliographic Information: Nakamura, T., Fujisawa, Y., Smith, B. R. M., Tomoda, N., Hasiweder, T. J., & Okada, Y. (Year). Revealing Pronounced Electron-Hole Fermi Pockets in the Charge Density Wave Semimetal LaTe3. [Journal Name].
Research Objective: This research paper investigates the electronic structure and many-body interactions in LaTe3, a non-magnetic member of the rare-earth tritelluride (RTe3) family known for its charge density wave (CDW) properties. The study aims to understand the fundamental Fermiology of LaTe3 and its implications for the broader RTe3 family.
Methodology: The researchers employed spectroscopic-imaging scanning tunneling microscopy (SI-STM) to perform Landau level spectroscopy on high-quality single crystals of LaTe3 at a temperature of 300 mK and under varying magnetic fields up to 15 T.
Key Findings: The study revealed the presence of pronounced electron and hole Fermi pockets of comparable sizes in LaTe3. Additionally, the researchers observed a dispersion kink near the Fermi level, indicative of electron-boson coupling in both the electron and hole bands. The electron-phonon coupling constant (λ) for the electron band was estimated to be 0.19 ± 0.01, suggesting weak coupling.
Main Conclusions: The identification of electron-hole Fermi pockets and the observation of electron-boson coupling in LaTe3 provide crucial insights into the electronic properties of this material. The researchers suggest that the interactions and instabilities arising from these Fermi pockets could be key to understanding the emergence of exotic electronic phases in other RTe3 compounds, particularly those exhibiting antiferromagnetism.
Significance: This research significantly contributes to the understanding of CDW semimetals and the interplay between Fermi surface topology, electron-boson coupling, and the emergence of novel electronic phases in quantum materials. The findings have implications for the development of materials with tailored electronic properties for potential applications in quantum technologies.
Limitations and Future Research: The study primarily focuses on the electronic properties of LaTe3 at low temperatures. Further research exploring the temperature dependence of the observed phenomena and investigating other RTe3 compounds could provide a more comprehensive understanding of the interplay between CDW, magnetism, and electron-boson coupling in these materials.

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The CDW wave vector in LaTe3 is approximately (5/7)qc.
The characteristic energy scale of the axial Higgs-like bosonic mode in LaTe3 is ~10 meV.
The electron-phonon coupling constant (λ) for the electron band in LaTe3 is estimated to be 0.19 ± 0.01.
The Fermi wave vector (kF) for the electron and hole bands are 0.146(5) Å⁻¹ and 0.227(1) Å⁻¹, respectively.
The area of the Fermi surface (AFS) relative to the area of the Brillouin zone (ABZ) for the electron and hole bands are 3.39(1)% and 8.00(1)%, respectively.

Quotes

Key Insights Distilled From

Revealing Pronounced Electron-Hole Fermi Pockets in the Charge Density Wave Semimetal LaTe3

by T. Nakamura,... at arxiv.org 11-12-2024

https://arxiv.org/pdf/2411.06664.pdf

Revealing Pronounced Electron-Hole Fermi Pockets in the Charge Density Wave Semimetal LaTe3

Deeper Inquiries

How does the electron-boson coupling strength vary across different members of the RTe3 family, and how does this variation correlate with the emergence of different electronic phases?

The strength of electron-boson coupling in RTe3 compounds is expected to be influenced by the specific rare-earth element (R) present.  Here's a breakdown of how this coupling might vary and its implications:

Heavier R elements: Compounds with heavier R elements (like Ce, Tb, Dy) tend to exhibit stronger electron-phonon coupling. This is linked to the larger ionic radii of these elements, leading to a stronger influence on the Te-Te bonding within the Te square net.  Stronger electron-phonon coupling can enhance the tendency towards charge density wave (CDW) instabilities, as observed in these materials. Additionally, the presence of 4f electrons in these heavier R elements introduces a new degree of freedom. The interaction between these localized 4f electrons and the conducting electrons in the Te layers can lead to Kondo effects, heavy fermion behavior, and complex magnetic ordering, further enriching the electronic phase diagram.

Lighter R elements:  In contrast, LaTe3, with the lighter La atom, exhibits weaker electron-phonon coupling. This is reflected in the smaller coupling constant (λ = 0.19) determined from the Landau level spectroscopy. The weaker coupling in LaTe3 makes it less susceptible to CDW formation at low temperatures, and indeed, only the high-temperature CDW1 phase is observed.

Correlation with Electronic Phases: The variation in electron-boson coupling strength directly correlates with the emergence of different electronic phases in the RTe3 family. Stronger coupling favors CDW formation and can even influence the CDW transition temperatures. For example, the heavier RTe3 compounds often exhibit multiple CDW transitions, while LaTe3 only shows one. Moreover, the interplay between electron-phonon coupling and the interaction between 4f and conduction electrons can give rise to exotic ground states like unconventional superconductivity and complex magnetic ordering, as observed in some RTe3 materials.

Could the observed electron-hole Fermi pockets in LaTe3 be manipulated or tuned through external stimuli such as pressure or doping to induce more exotic electronic ground states?

Yes, the observed electron-hole Fermi pockets in LaTe3 present a promising platform for manipulation via external stimuli like pressure and doping, potentially leading to the emergence of exotic electronic ground states. Here's why:

Pressure: Applying pressure can modify the lattice constants and, consequently, the electronic band structure of LaTe3. This can lead to:

Fermi surface nesting: Pressure could tune the electron and hole Fermi pockets to perfectly nest, enhancing the interaction between electrons and holes. This nesting condition is often a key ingredient for the formation of excitonic insulators or unconventional density wave states.
Enhanced electron-phonon coupling: Pressure can also enhance the electron-phonon coupling strength, potentially pushing LaTe3 towards a regime where multiple CDW transitions or even unconventional superconductivity might emerge.

Doping: Introducing dopants into LaTe3 can alter the carrier concentration and influence the electronic correlations, leading to:

Lifted Fermi surface degeneracy: Doping can lift the degeneracy between the electron and hole pockets, potentially favoring the formation of more exotic ground states.
Modified electronic interactions: Doping can introduce disorder or modify the screening of Coulomb interactions, potentially tipping the balance towards different electronic instabilities.

Examples in RTe3 Family: The potential for inducing exotic states through pressure and doping is supported by observations in other RTe3 compounds. For instance, pressure-induced superconductivity has been reported in TbTe3, highlighting the sensitivity of these materials to external stimuli.

What are the potential implications of the observed electron-boson coupling in LaTe3 for the development of novel quantum materials with enhanced superconducting or topological properties?

The observed electron-boson coupling in LaTe3, while weak, holds intriguing implications for the development of novel quantum materials, particularly in the context of superconductivity and topological phases:

Unconventional Superconductivity: Even though LaTe3 itself is not superconducting, the presence of electron-boson coupling, as evidenced by the Landau level spectroscopy, suggests that related compounds with stronger coupling could host unconventional superconductivity. This is particularly relevant considering the close relationship between LaTe3 and other RTe3 members where pressure-induced superconductivity has been observed. By understanding the interplay between electron-boson coupling, Fermi surface topology, and magnetic interactions in these materials, researchers could potentially design new RTe3-based superconductors with higher critical temperatures or novel pairing mechanisms.

Topological Materials: The electron-hole Fermi pockets in LaTe3, combined with the possibility of tuning the band structure through pressure or doping, open avenues for exploring topological phases. For instance, by manipulating the Fermi level and inducing band inversions, it might be possible to drive LaTe3 into a topological insulator or a Dirac semimetal phase. The presence of electron-boson coupling could further enrich the topological properties of these phases, potentially leading to the discovery of novel topological superconducting states.

Quantum Material Design: More broadly, the insights gained from studying electron-boson coupling in LaTe3 contribute to a deeper understanding of how electronic correlations and interactions can give rise to exotic phases in quantum materials. This knowledge is crucial for the rational design of new materials with tailored properties, paving the way for advancements in areas such as quantum computing, spintronics, and energy applications.