Nav: Home

Topological semimetals can generate sizable transverse thermoelectric figure of merit

December 31, 2019

The thermoelectric conversion efficiency of a particular material is determined by the value of its thermoelectric figure of merit zT. It is a complex function of the absolute temperature and several pertinent transport properties including the Seebeck coefficient, the electrical and thermal conductivities. These quantities are usually measured in parallel to each other, reflecting the longitudinal thermoelectric effect.

Optimization of zT in conventional thermoelectric materials meets severe limitations. For instance, one comes from the charge compensation of electrons and holes that contribute oppositely to the Seebeck effect. The other is the Wiedemann-Franz law that fundamentally ties the electrical and the thermal conductivity, making independent optimization of the two quantities impossible.

A recent paper of J. S. Xiang et al. published in Sci. China-Phys. Mech. Astron. has demonstrated a much larger transverse figure of merit in a topological semimetal in low magnetic fields, relative to its longitudinal counterpart. This simply resembles the much larger transverse (Hall) conductivity over its longitudinal counterpart that is generically observed in many topological semimetals in low fields.

The large transverse zT values in topological semimetal benefit from some of its inherent features. These include the coexistence of electrons and holes which, in the case of transverse thermoelectricity, will contribute additively to each other, and the topologically protected high charge mobility is, to a large extent, free of the lattice imperfection. Actually, the Dirac semimetal Cd3As2, which is focused in this paper, has a very high electron mobility in spite of its negligible lattice thermal conductivity for this reason.

More excitingly, topological semimetals can have excess transverse thermoelectric effect, known as anomalous Nernst effect, arising from the pronounced Berry curvature near the Fermi level. Furthermore, if one considers a magnetic topological semimetal, the large transverse thermoelectricity will appear in the absence of external field.

As the paper reads, the transverse thermoelectric effect offers some more merits over its longitudinal counterpart: one does not need two (n and p) types of thermoelectric materials for constructing one device; because the electrical and thermal currents are orthogonal and decoupled in this case, high electrical conductivity and low thermal conductivity desired for large transverse figure of merit can be easily realized by using an anisotropy compound.
This research was funded by the Ministry of Science and Technology of China (Grant Nos. 2017YFA0303100, and 2015CB921303), the National Natural Science Foundation of China (Grant Nos. 11774404, and 11474332), and the Chinese Academy of Sciences through the Strategic Priority Research Program (Grant No. XDB07020200).

See the article:

J. S. Xiang, S. L. Hu, M. Lyu, W. L. Zhu, C. Y. Ma, Z. Y. Chen, F. Steglich, G. F. Chen, and P. J. Sun, Large transverse thermoelectric figure of merit in a topological Dirac semimetal, Sci. China-Phys. Mech. Astron. 63, 237011 (2020).

Science China Press

Related Electrons Articles:

Self-imaging of a molecule by its own electrons
Researchers at the Max Born Institute (MBI) have shown that high-resolution movies of molecular dynamics can be recorded using electrons ejected from the molecule by an intense laser field.
Electrons in the fast lane
Microscopic structures could further improve perovskite solar cells
Laser takes pictures of electrons in crystals
Microscopes of visible light allow to see tiny objects as living cells and their interior.
Plasma electrons can be used to produce metallic films
Computers, mobile phones and all other electronic devices contain thousands of transistors, linked together by thin films of metal.
Flatter graphene, faster electrons
Scientists from the Swiss Nanoscience Institute and the Department of Physics at the University of Basel developed a technique to flatten corrugations in graphene layers.
Researchers develop one-way street for electrons
The work has shown that these electron ratchets create geometric diodes that operate at room temperature and may unlock unprecedented abilities in the illusive terahertz regime.
Photons and electrons one on one
The dynamics of electrons changes ever so slightly on each interaction with a photon.
Using light to put a twist on electrons
Method with polarized light can create and measure nonsymmetrical states in a layered material.
What if we could teach photons to behave like electrons?
The researchers tricked photons - which are intrinsically non-magnetic - into behaving like charged electrons.
Electrons in rapid motion
Researchers observe quantum interferences in real-time using a new extreme ultra-violet light spectroscopy technique.
More Electrons News and Electrons Current Events

Trending Science News

Current Coronavirus (COVID-19) News

Top Science Podcasts

We have hand picked the top science podcasts of 2020.
Now Playing: TED Radio Hour

Listen Again: The Power Of Spaces
How do spaces shape the human experience? In what ways do our rooms, homes, and buildings give us meaning and purpose? This hour, TED speakers explore the power of the spaces we make and inhabit. Guests include architect Michael Murphy, musician David Byrne, artist Es Devlin, and architect Siamak Hariri.
Now Playing: Science for the People

#576 Science Communication in Creative Places
When you think of science communication, you might think of TED talks or museum talks or video talks, or... people giving lectures. It's a lot of people talking. But there's more to sci comm than that. This week host Bethany Brookshire talks to three people who have looked at science communication in places you might not expect it. We'll speak with Mauna Dasari, a graduate student at Notre Dame, about making mammals into a March Madness match. We'll talk with Sarah Garner, director of the Pathologists Assistant Program at Tulane University School of Medicine, who takes pathology instruction out of...
Now Playing: Radiolab

Kittens Kick The Giggly Blue Robot All Summer
With the recent passing of Ruth Bader Ginsburg, there's been a lot of debate about how much power the Supreme Court should really have. We think of the Supreme Court justices as all-powerful beings, issuing momentous rulings from on high. But they haven't always been so, you know, supreme. On this episode, we go all the way back to the case that, in a lot of ways, started it all.  Support Radiolab by becoming a member today at