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arxiv: 2602.14959 · v2 · pith:BLK2RYXPnew · submitted 2026-02-16 · ❄️ cond-mat.mtrl-sci · physics.optics

Large Transverse Thermoelectric Effect in Weyl Semimetal TaIrTe₄ Engineered for Photodetection

Morgan G. Blevins , Xianglin Ji , Vivian J. Santamaria-Garcia , Abhishek Mukherjee , Thanh Nguyen , Mingda Li , Svetlana V. Boriskina This is my paper

Pith reviewed 2026-05-21 12:53 UTC · model grok-4.3

classification ❄️ cond-mat.mtrl-sci physics.optics
keywords Weyl semimetalTaIrTe4transverse thermoelectric effectphotocurrentphotodetectionanisotropic Seebeck coefficienttopological semimetal
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The pith

Anomalous photocurrents in TaIrTe4 arise from its large transverse thermoelectric effect due to anisotropic Seebeck coefficients.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper shows that photocurrents generated in the Weyl semimetal TaIrTe4 under visible or far-infrared light come from a transverse thermoelectric response rather than from nonlinear charge currents. The authors demonstrate that aligning the crystal edges with electrodes and changing the thermal environment through substrate choices lets them control where the current appears and how strong it becomes. This approach turns an intrinsic material anisotropy into a practical handle for designing detectors that work across a wide range of wavelengths. A reader would care because it offers a route to simpler, geometry-tunable photodetectors for tasks such as tracking light beams or sensing wavefronts without needing extra optical components.

Core claim

Anomalous local photocurrents in TaIrTe4 under far-field illumination originate from the large transverse thermoelectric effect produced by the material's anisotropic Seebeck coefficients. By engineering the mutual orientation of crystal edges and electrodes together with the thermal environment, the spatial photocurrent response can be controlled and amplified. Substrate engineering further allows local enhancement of the photocurrent, supplying a framework for broadband photodetection that exploits both spectral and spatial dependence.

What carries the argument

the large transverse thermoelectric effect arising from anisotropic Seebeck coefficients in the C2v crystal symmetry of TaIrTe4

Load-bearing premise

The observed photocurrents are dominated by the anisotropic Seebeck coefficients rather than residual nonlinear responses or contact effects, and substrate modifications enhance only the thermoelectric contribution.

What would settle it

A measurement that isolates thermal conductivity changes (for example by swapping substrates of different heat-spreading properties) while keeping optical absorption and electrical contacts fixed, then checks whether the photocurrent magnitude and spatial pattern still track the expected thermoelectric pattern.

Figures

Figures reproduced from arXiv: 2602.14959 by Abhishek Mukherjee, Mingda Li, Morgan G. Blevins, Svetlana V. Boriskina, Thanh Nguyen, Vivian J. Santamaria-Garcia, Xianglin Ji.

Figure 1
Figure 1. Figure 1: FIG. 1 [PITH_FULL_IMAGE:figures/full_fig_p003_1.png] view at source ↗
Figure 2
Figure 2. Figure 2: FIG. 2 [PITH_FULL_IMAGE:figures/full_fig_p005_2.png] view at source ↗
Figure 3
Figure 3. Figure 3: FIG. 3 [PITH_FULL_IMAGE:figures/full_fig_p006_3.png] view at source ↗
Figure 4
Figure 4. Figure 4: FIG. 4 [PITH_FULL_IMAGE:figures/full_fig_p009_4.png] view at source ↗
read the original abstract

Anomalous local photocurrent generation via second-order nonlinear and thermoelectric responses is a signature of many topological semimetals. The emergence of these photocurrents is inherently linked to symmetry breaking and anisotropy of their crystal lattices. Studies of type-II Weyl semimetals of group C$_{2v}$ (WTe$_2$, MoTe$_2$, TaIrTe$_4$) have reported anomalous, nonlocal photocurrents localized to crystals edges or far from electrodes, which are highly dependent on the geometry of the material sample. While originally attributed to a nonlinear charge current response, it was recently shown that these currents could instead be attributed to the anisotropic Seebeck coefficients of the materials. Here, we confirm that anomalous photocurrents observed in TaIrTe$_4$ under either visible or far-infrared far-field illumination originate from the large transverse thermoelectric effect. We engineer the mutual orientation of crystal edges and electrodes as well as the thermal environment of TaIrTe$_4$ to control and amplify its spatial photocurrent response. We show that substrate engineering can locally enhance photocurrent. This framework of thermal device engineering can enable broadband photo detection schemes by leveraging spectral and spatial dependence of photocurrents for applications like wavefront sensing, beam positioning, and edge detection.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

1 major / 1 minor

Summary. The manuscript claims that anomalous photocurrents in TaIrTe4 under visible or far-infrared far-field illumination originate from the large transverse thermoelectric effect due to anisotropic Seebeck coefficients. The authors engineer crystal-edge/electrode orientations and the thermal environment (including substrate changes) to control and amplify the spatial photocurrent response, proposing this approach for broadband photodetection applications such as wavefront sensing, beam positioning, and edge detection.

Significance. If the thermoelectric attribution is quantitatively established, the work supplies a concrete engineering framework for leveraging transverse thermoelectric responses in Weyl semimetals, enabling spatial and spectral control of photocurrents that could support practical optoelectronic devices beyond conventional nonlinear mechanisms.

major comments (1)
  1. [Experimental results] Experimental results section: The central claim that observed photocurrents are dominated by the anisotropic Seebeck response (rather than residual nonlinear or contact effects) lacks a quantitative match to predictions. No local thermometry, heat-flow modeling, or direct comparison of measured current amplitudes and spatial maps against the Seebeck tensor acting on the actual temperature profile is reported, leaving the dominance unverified.
minor comments (1)
  1. [Abstract] Abstract: The statement that substrate engineering 'can locally enhance photocurrent' would benefit from a specific factor or percentage improvement to convey the magnitude of the effect.

Simulated Author's Rebuttal

1 responses · 0 unresolved

We thank the referee for the careful reading and constructive feedback. The point raised about quantitative validation of the thermoelectric mechanism is well taken, and we address it directly below while proposing concrete revisions.

read point-by-point responses

  1. Referee: Experimental results section: The central claim that observed photocurrents are dominated by the anisotropic Seebeck response (rather than residual nonlinear or contact effects) lacks a quantitative match to predictions. No local thermometry, heat-flow modeling, or direct comparison of measured current amplitudes and spatial maps against the Seebeck tensor acting on the actual temperature profile is reported, leaving the dominance unverified.

    Authors: We agree that a direct quantitative comparison would strengthen the central claim. The present manuscript demonstrates that photocurrent spatial maps and amplitudes can be systematically controlled by crystal-edge/electrode orientation and by substrate thermal engineering, and that these controls produce responses consistent with the known anisotropic Seebeck tensor of TaIrTe4. However, we did not perform local thermometry or include an explicit heat-flow model that folds the measured temperature profile into the Seebeck tensor to predict current amplitudes. In the revised manuscript we will add a finite-element heat-flow simulation of the illuminated device geometry together with a side-by-side comparison of the calculated versus measured photocurrent amplitudes and spatial profiles. This addition will allow a quantitative test of whether the anisotropic Seebeck response accounts for the observed signals without invoking additional mechanisms. revision: yes

Circularity Check

0 steps flagged

No circularity: experimental engineering confirms external attribution without self-referential derivation

full rationale

The paper's central contribution is experimental: engineering crystal/electrode/substrate orientations to control and amplify observed photocurrents in TaIrTe4 under visible and far-IR illumination, confirming their origin in the transverse thermoelectric effect. This attribution rests on a cited recent external demonstration rather than any internal derivation, fit, or self-citation chain. No equations or predictions are presented that reduce by construction to the paper's own inputs; the work is self-contained as an empirical demonstration against external benchmarks, with no load-bearing self-referential steps.

Axiom & Free-Parameter Ledger

0 free parameters · 1 axioms · 0 invented entities

Abstract supplies no explicit free parameters or invented entities; the central claim rests on the domain assumption that anisotropic Seebeck coefficients dominate the observed photocurrent spatial pattern.

axioms (1)
  • domain assumption Anisotropic Seebeck coefficients produce the observed transverse thermoelectric photocurrents in C2v Weyl semimetals
    Invoked to reinterpret prior anomalous photocurrent data as thermoelectric rather than nonlinear.

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