Anomalous Transverse Thomson Effect

summary

The gist

The anomalous Thomson effect (ATE) is formulated as a Thomson counterpart to the anomalous Hall and Nernst effects, providing a mechanism for solid-state thermoelectric refrigeration in specific

In short

The anomalous transverse Thomson effect (ATTE) is a long-missing counterpart to anomalous Hall and Nernst effects, offering a mechanism for solid-state thermoelectric refrigeration. The study shows that the ratio of ATTE coefficient to the total anomalous Nernst coefficient approaches three at low temperatures. Furthermore, for CeCrGe3, the ATTE can be ten times larger than the ANC at liquid nitrogen temperatures.

Key concepts

Anomalous Transverse Thomson Effect (ATTE): The ATTE is a theoretical effect that acts as a Thomson counterpart to anomalous Hall and Nernst effects. It describes how an imposed current density interacts with temperature gradients in magnetic materials, providing a pathway for solid-state thermoelectric refrigeration.
Anomalous Nernst Coefficient (ANC): The ANC quantifies the response of a material to a temperature gradient when subjected to a magnetic field. This coefficient is crucial because it is related to the ATTE; both are determined by the total ANC and its temperature dependence, regardless of whether its origin is intrinsic or extrinsic.
Berry Curvature: In topological materials like Fe3Sn2, Berry curvature arises from the band structure near gapped Dirac cones. The paper shows that this Berry curvature significantly enhances the contributions to the ANC-related terms of the ATTE, leading to stronger effects in these specific materials.
Longitudinal Resistivity: The temperature dependence of longitudinal resistivity plays an additional role in determining the ATTE coefficient, especially when considering equipotential electrodes. This dependence is necessary for fully determining $ au_{ m ATTE}^{(E)}$ and is model-independent within local linear response.

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This episode discusses

Anomalous Transverse Thomson Effect · Paper Radio

The paper

Anomalous Transverse Thomson Effect · Read on arXiv

Ying-Fei Zhang, Zhi-Fan Zhang, Zhen-Gang Zhu, * and Gang Su

School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100049, China. · Interdisciplinary Center for Theoretical Physics and Information Sciences (ICTPIS), Fudan University, Shanghai 200433, China. · School of Electronic, Electrical and Communication Engineering, University of Chinese Academy of Sciences, Beijing 100049, China. · Institute of Theoretical Physics, Chinese Academy of Sciences, Beijing 100190, China. · Kavli Institute for Theoretical Sciences, University of Chinese Academy of Sciences, Beijing 100190, China.

Transcript

Introduction to the show: ident: Quantum Radio. Generated commentary on the latest quantum physics and condensed matter papers.

Kai: I'm Kai, and with me are Mira and Lev, guest researcher.

Mira: Today's paper: "Anomalous Transverse Thomson Effect".

Kai: The anomalous Thomson effect (ATE) is formulated as a Thomson counterpart to the anomalous Hall and Nernst effects, providing a mechanism for solid-state thermoelectric refrigeration in specific materials.

Mira: First, who's behind it and why it matters.

Title and authors: Kai: So we're looking at this paper, "Anomalous Transverse Thomson Effect," and it introduces something called the anomalous Thomson effect, which they frame as a counterpart to the anomalous Hall effect and anomalous Nernst effect.

Mira: It sounds like they're trying to create a mechanism for solid-state refrigeration using these effects in specific materials.

Kai: Right, so it suggests that if you apply a current and a temperature gradient perpendicularly, you can get this transverse thermal response.

Lev: From where I stand, this means we need to look at the underlying physics of how those currents and gradients interact with the material's magnetic properties.

The paper's summary: Mira: So, they summarize it by saying the anomalous Thomson coefficient, ATC, is determined by combining the anomalous Nernst coefficient, ANC, with how both of those things and electrical conductivity change with temperature.

Kai: That’s a bit more detail than just saying it's a counterpart to other effects. It seems like they're making a specific formula for this new effect based on what we already know about the ANC.

Mira: Exactly, and they state that this relationship is model independent within local linear response, meaning it should hold true regardless of whether the anomalous Nernst effect comes from intrinsic things or something extrinsic.

Lev: That's a big deal for experimentalists because it suggests we might be able to use existing measurements of conductivity and transport coefficients to predict this effect without having to develop a whole new microscopic model from scratch.

The paper's improvements: Kai: They also point out how the anomalous Thomson coefficient, ATC, gets its value from three different contributions when you look at the formula they have.

Mira: It breaks down into one term describing the temperature evolution of the ANC, and another term that comes from a local energy balance at that specific spot.

Kai: So it’s not just one simple relationship; it’s a combination of thermal changes and local energy considerations driving the effect.

Lev: That points to where we need to focus our attention for practical implementation, because understanding those separate contributions helps us figure out what's controlling the magnitude of the cooling or heating.

Conclusion: Mira: So, wrapping up, the paper suggests that this anomalous Thomson effect could be useful for solid-state thermoelectric refrigeration in materials where certain conditions are met.

Kai: And they show some specific examples, like CeCrGe3, where they found the ATC can be ten times larger than the ANC at liquid nitrogen temperatures.

Lev: For hardware design, that magnitude is what matters; having a factor of ten difference between these two coefficients opens up possibilities for much stronger cooling capabilities than we might expect from just looking at one effect alone.

Mira: Indeed, and they also mention how the dimensionless ratio of ATC to ANC converges to three in the low-temperature limit.

Kai: So, just to recap, this paper lays out a way to calculate this effect using known data and shows that for some materials like CeCrGe3, it could offer a substantial enhancement over other known anomalous effects.

Lev: It’s interesting because it connects the theory directly to the potential for real-world cooling performance.

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