Kagome metals deliver giant transverse thermoelectricity without magnetic fields

The kagome metal LuCo₆Ge₆ exhibits opposite carrier polarities along different crystallographic directions, producing a giant transverse thermoelectric response without magnetic fields. The discovery establishes a new design principle that exploits kagome electronic structures for efficient energy conversion.

To the point:

Goniopolarity and extraordinary performance: Axis-dependent carrier polarity (goniopolarity), in combination with flat-band and van Hove singularity states, enable transverse thermopower of 18.4 μV K^-1 and transverse Peltier conductivity of 105 A m^-1 K^-1 at room temperature and zero field in kagome metal LuCo₆Ge₆.

Advanced design strategy: This fermiology-driven transport avoids magnetic field issues and may apply to other topological and quantum materials. This enables advances in solid-state cooling and waste heat recovery.

Expert statement: Prof. Claudia Felser highlights that exploiting kagome electronic structures creates a novel path for next-generation thermoelectric devices without relying on magnetic order.

Researchers from the Max Planck Institute for Chemical Physics of Solids (MPI CPfS) have uncovered goniopolarity for generating giant transverse thermoelectricity in kagome metals without applying magnetic fields. By exploiting goniopolar transport, the researchers achieved record room-temperature transverse thermoelectric performance in LuCo₆Ge₆. Their work reveals that characteristic kagome electronic structures, including flat bands and van Hove singularities, naturally promote this unusual transport behavior, providing a fundamentally new strategy for designing high-performance thermoelectric materials.

Kagome electronic structures offer a new opportunity

Kagome materials have become a fascinating platform for quantum materials research because their corner-sharing lattice hosts a variety of exotic electronic states, including Dirac fermions, flat bands, van Hove singularities and unconventional superconductivity. While these electronic features have mainly been explored in the context of topology and correlated electron physics, their potential for thermoelectric energy conversion has remained largely unexplored.

The present study demonstrates that kagome fermiology itself can generate a large transverse thermoelectric response. Unlike conventional transverse thermoelectric materials, which rely on magnetic order and fields, goniopolarity-driven transverse thermoelectrics can operate in paramagnetic material under zero magnetic field. Goniopolarity, also known as axis-dependent carrier polarity, creates a transverse voltage when a temperature gradient is applied, opening a potential route for transverse thermoelectric conversion.

Two microscopic mechanisms discovered

Combining theoretical calculation and experimental measurements, the researchers identified two distinct microscopic mechanisms responsible for goniopolar transport in kagome metals.

In LuCo₆Ge₆, a flat-band-derived Fermi pocket cooperates with an electron-like pocket to generate opposite carrier polarities along different crystallographic directions. By contrast, LuCr₆Ge₆ and HoCr₆Ge₆ exhibit a second mechanism driven by anisotropic particle-hole asymmetry associated with van Hove singularities. These findings establish a direct connection between kagome Fermi-surface geometry and transverse thermoelectric transport. Rather than depending on Berry curvature, the transport properties emerge directly from the anisotropic electronic structure near the Fermi level.

Record transverse thermoelectric performance

Among the investigated compounds, LuCo₆Ge₆ exhibits extraordinary room-temperature performance. At 300 K and zero magnetic field, the material reaches a transverse thermopower of 18.4 μV K^_–1, a transverse Peltier conductivity of 105 A m^–1 K^–1, and a transverse power factor of 8.2 μW cm^–1 K^–2. These values exceed those reported for existing zero-field anomalous Nernst materials (maximum value: ~6 μV K^–1 at 300 K).

"The most exciting part of this work was uncovering how the unique kagome Fermi surface governs transverse charge transport," says first author Dr. Haihua Hu, a researcher at the MPI CPfS. "Our results reveal the microscopic origin of giant transverse thermoelectricity without magnetic fields, directly linking goniopolarity to the kagome electronic structure."

The discovery establishes fermiology-driven goniopolar transport as a promising design principle for transverse thermoelectrics. Because the mechanism does not require magnetic order, it avoids issues associated with stray magnetic fields while maintaining excellent thermoelectric performance. The researchers anticipate that this concept can be extended beyond kagome metals to a broad class of topological and quantum materials, providing new opportunities for compact solid-state cooling and waste-heat recovery technologies.

“Our work demonstrates that the unique electronic structure of kagome materials can be directly exploited to generate giant transverse thermoelectricity without magnetic fields,” says Prof. Claudia Felser, Director at MPI CPfS and corresponding author of this study. “This fermiology-driven mechanism opens a fundamentally new direction for designing next-generation thermoelectric materials and devices.”