Pressure-Tuned Anomalous Hall Effect in CrGeTe3: Unveiling the Interplay of Intrinsic and Extrinsic Contributions

Conceitos Básicos

This study investigates the pressure-dependent behavior of the anomalous Hall effect (AHE) in CrGeTe3, revealing a complex interplay of intrinsic Berry curvature and extrinsic scattering mechanisms that can be tuned by pressure.

Resumo

• Bibliographic Information: Scharf, G., Guterding, D., Hen, B., Sarte, P. M., Ortiz, B. R., Rozenberg, G. K., ... & Ron, A. (2024). Pressure tuning of intrinsic and extrinsic sources to the anomalous Hall effect in CrGeTe3. arXiv preprint arXiv:2401.09539v3.
• Research Objective: This study aims to investigate the evolution of the anomalous Hall effect (AHE) in CrGeTe₃ under varying hydrostatic pressure, focusing on the interplay between intrinsic Berry curvature and extrinsic scattering mechanisms.
• Methodology: The researchers employed a combination of experimental measurements and ab-initio density functional theory (DFT) calculations. Experimentally, they measured the AHE in CrGeTe₃ crystals under high pressure using a diamond anvil cell. Theoretically, they calculated the electronic band structure, Fermi surface, Berry curvature, and AHE conductivity as a function of pressure.
• Key Findings: The study reveals a dome-like pressure dependence of the AHE in CrGeTe₃, coinciding with Fermi surface deformations and mixed electron-hole transport. DFT calculations confirm the pressure-induced modulation of Berry curvature and AHE conductivity. However, quantitative discrepancies between experimental and theoretical results suggest significant contributions from extrinsic scattering mechanisms, particularly side jump scattering.
• Main Conclusions: The AHE in CrGeTe₃ is highly sensitive to pressure, exhibiting a non-monotonic behavior attributed to the intricate interplay of intrinsic and extrinsic contributions. While Berry curvature plays a role, the study highlights the significant influence of pressure-dependent extrinsic scattering mechanisms, particularly side jump scattering, on the observed AHE.
• Significance: This research provides valuable insights into the complex interplay of intrinsic and extrinsic contributions to the AHE in a ferromagnetic material. The findings emphasize the importance of considering both intrinsic and extrinsic mechanisms when interpreting AHE data, particularly in systems with strong pressure-dependent electronic structure modifications.
• Limitations and Future Research: The study acknowledges the challenge of precisely calculating extrinsic scattering contributions due to the unknown scattering potential. Future research could explore advanced theoretical methods to quantify these effects accurately. Additionally, investigating the pressure dependence of AHE in other magnetic materials with similar electronic structure characteristics could further elucidate the interplay of intrinsic and extrinsic mechanisms.

Estatísticas

CrGeTe3 undergoes an insulator-to-metal transition at approximately 6 GPa.
The Curie temperature of CrGeTe3 initially decreases with pressure up to 4.5 GPa and then increases dramatically to approximately 250 K at 9.1 GPa.
The Hall coefficient of CrGeTe3 exhibits a dome-like behavior as a function of pressure, indicating mixed electron and hole transport at the edges of the dome.
The AHE in CrGeTe3 persists to temperatures significantly higher than the Curie temperature at ambient pressure, suggesting a pressure-induced enhancement of the Curie temperature.
The AHE in CrGeTe3 exhibits a dome-like pressure dependence, with the dome's onset coinciding with the insulator-to-metal transition.
DFT calculations reveal that the total Berry curvature in CrGeTe3 is substantially modulated by pressure.
The calculated AHE conductivity shows a strong pressure dependence, with a sign change at intermediate pressures.

Citações

"Quantitative discrepancies between our calculations and experimental results indicate that additional scattering mechanisms, which are also strongly tuned by pressure, contribute to the anomalous Hall effect in CrGeTe3."
"The AHE dome coincides with the pressure range where Fermi surface deformations are observed through the ordinary Hall effect."
"Our ab-initio calculations corroborate the presence of electron and hole pockets in the Fermi surface both of which host nonzero integrated Berry curvature."
"This shows that the Berry curvature is not the sole contribution to the anomalous Hall conductivity in CrGeTe3 and that extrinsic mechanisms must also be at play."

Principais Insights Extraídos De

Pressure tuning of intrinsic and extrinsic sources to the anomalous Hall effect in CrGeTe$_3$

by Gili Scharf,... às arxiv.org 11-08-2024

https://arxiv.org/pdf/2401.09539.pdf

Perguntas Mais Profundas

How does the pressure-induced modulation of the AHE in CrGeTe3 compare to that observed in other magnetic materials with similar electronic structures?

The pressure-induced modulation of the Anomalous Hall Effect (AHE) in CrGeTe3, exhibiting a dome-like behavior with pressure, is quite unique compared to other magnetic materials with similar electronic structures. Here's a breakdown:

Uniqueness of the Dome-Shape: Most ferromagnetic materials demonstrate a monotonic change in AHE with applied pressure. This means the AHE either increases or decreases continuously with pressure, as seen in materials like CeAlSi (skew scattering dominated) or Co3Sn2S2 (intrinsic Berry curvature dominated). The dome-like behavior in CrGeTe3, where the AHE rises to a maximum and then decreases, suggests a more complex interplay of intrinsic and extrinsic contributions.

Role of Fermi Surface Deformations: The edges of the AHE dome in CrGeTe3 coincide with pressures where the material exhibits mixed electron and hole transport, a clear sign of pressure-induced Fermi surface deformations. This is significant because it directly links changes in the electronic structure to the AHE modulation. While pressure can alter the electronic structure in other materials too, a direct correlation with such a distinct AHE behavior is not commonly observed.

Importance of Extrinsic Mechanisms: The study highlights that while Berry curvature changes contribute to the AHE modulation in CrGeTe3, extrinsic mechanisms, particularly side-jump scattering, are likely dominant. This is in contrast to materials where the intrinsic Berry curvature is the primary driver of AHE. The significant changes in CrGeTe3's band structure and Bloch wavefunctions with pressure further underscore the sensitivity of extrinsic mechanisms to pressure.
In essence, the pressure-tuned AHE in CrGeTe3 stands out due to its non-monotonic behavior, the clear link to Fermi surface changes, and the significant role of pressure-sensitive extrinsic scattering mechanisms. This contrasts with the more straightforward pressure responses observed in many other magnetic materials, making CrGeTe3 an intriguing case study.

Could the observed AHE behavior be attributed to a change in the magnetic ordering of CrGeTe3 under pressure, rather than solely to changes in the electronic structure and scattering mechanisms?

While the study heavily emphasizes the role of electronic structure and scattering mechanisms in the pressure-tuned AHE of CrGeTe3, a change in magnetic ordering under pressure could also be a contributing factor. Here's why:

Pressure Effects on Magnetism: It's well-established that applying pressure can alter the magnetic properties of materials. Pressure can influence the exchange interactions between magnetic moments, potentially leading to changes in the magnetic ordering temperature (Curie temperature), the type of magnetic order (e.g., ferromagnetic to antiferromagnetic), or even the emergence of new magnetic phases.

AHE Sensitivity to Magnetic Order: The AHE is inherently sensitive to the magnetic state of a material. Different magnetic orderings can result in different contributions to the AHE. For instance, a transition from ferromagnetic to antiferromagnetic order could significantly alter the AHE signal.

Indirect Evidence in CrGeTe3: The study observes an apparent enhancement of the Curie temperature with pressure in CrGeTe3, as evidenced by the persistence of the AHE signal at temperatures far exceeding the ambient pressure Curie temperature. While this is attributed to pressure-enhanced ferromagnetism, it could also indicate a more complex evolution of the magnetic order.

Need for Further Investigation: To definitively disentangle the roles of magnetic ordering changes and electronic structure modifications in the pressure-tuned AHE of CrGeTe3, further investigations are needed. Techniques like neutron diffraction under pressure could provide direct insights into the evolution of the magnetic order, while pressure-dependent magnetization measurements could shed light on changes in the magnetic anisotropy.
In conclusion, while the study focuses on electronic and scattering mechanisms, a potential change in the magnetic ordering of CrGeTe3 under pressure cannot be ruled out as a contributing factor to the observed AHE behavior. Further research is crucial to fully elucidate the interplay between pressure, magnetism, and the AHE in this material.

What are the potential implications of pressure-tunable AHE for developing novel spintronic devices?

The pressure-tunable AHE observed in CrGeTe3 presents exciting possibilities for developing novel spintronic devices. Here's a glimpse into the potential implications:

Pressure-Controlled Spin Current Generation: The AHE enables the generation of spin currents, which are essential for spintronic applications. The ability to tune the AHE magnitude and even its sign in CrGeTe3 using pressure opens avenues for creating pressure-controlled spin current generators. This could lead to devices where the spin current can be switched on/off or modulated by applying pressure.

Strain-Engineered Spintronic Devices: Pressure can induce strain in materials. The sensitivity of the AHE in CrGeTe3 to pressure suggests that it might also be highly sensitive to strain. This opens possibilities for strain-engineered spintronic devices, where the AHE and consequently the spin-dependent transport properties can be controlled by applying mechanical strain.

Integration with 2D Materials: CrGeTe3 is a van der Waals material, meaning it can be exfoliated into thin layers. This property, combined with the pressure-tunable AHE, makes it a promising candidate for integration into van der Waals heterostructures. One could envision devices where CrGeTe3 layers are interfaced with other 2D materials, and the AHE is controlled by applying pressure to the entire heterostructure.

Beyond Binary Logic: The non-monotonic, dome-like behavior of the AHE in CrGeTe3 is particularly intriguing. This kind of response could potentially be exploited for developing spintronic devices that go beyond simple binary logic (0 or 1). For instance, one could envision multi-level logic devices where different pressure ranges correspond to distinct AHE values, representing different logic states.

Challenges and Opportunities: Realizing these potential applications requires overcoming challenges related to integrating pressure or strain application into device architectures, ensuring the stability of CrGeTe3 under pressure, and understanding the temperature dependence of the pressure-tuned AHE. However, the unique properties of CrGeTe3 make it a fertile ground for exploring new spintronic device concepts.
In summary, the pressure-tunable AHE in CrGeTe3 offers a new knob for manipulating spin-dependent transport properties. This discovery could pave the way for developing novel spintronic devices with enhanced functionalities, potentially leading to advancements in data storage, information processing, and sensing technologies.