Realization of Large Thermopower Using Semimetals and Narrow-Gap Semiconductors in a Magnetic Field

Applications

Thermoelectric materials are vital for the development of thermoelectric generators and coolers used in manufacturing processes. These materials can save energy and money with heating processes.

Problem Addressed

Thermoelectric materials are a useful tool in generating power from waste heat or transforming electric current into cooling power. Finding materials with large thermopower is vital for the development of thermoelectric generators and thermoelectric coolers. The effectiveness of a thermoelectric material for power applications is quantified by its thermoelectric figure of merit, ZT. In an insulator, thermopower is large, but since conductivity is low, ZT is characteristically low. Metals have robust conductivity yet lack strong thermopower so they yield relatively low ZT.

Technology

The limitations of metals and insulators can be overcome through the use of doped nodal semimetals in a strong magnetic field. The magnetic field ensures that the transverse drift of both electrons and holes contribute additively to the thermopower. Within a sufficiently high magnetic field, a large enhancement of the electronic density of states and a reduction in the Fermi energy occurs. Since the thermoelectrode materials have small band gaps and electron-hole symmetry in their band structure, concentrations of thermally excited electrons and holes both grow - even while their difference remains fixed. These magnetic field effects allow the thermopower to grow without saturation.

Advantages

  • Substantial thermopower generated from device is amplified by magnetic field allowing ZT to grow without saturation
  • Generates an electric field/cooling effect along two directions