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Strongly Interacting Electrons in NaxCoO2
- a Quantum Game of Go on a Triangular Lattice
A magnetic field kills the heat-carrying
capability of the electron spins as shown by the red curve.
Inset depicts the Go-like hops of electrons moving in the
NaxCoO2 crystal lattice.
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IRG1: Y. Wang, N.S. Rogado, R.J. Cava, N.P. Ong
Oxide materials exhibit many useful properties for potential applications.
The cobalt oxide NaxCoO2 exhibits a large
thermoelectric effect. It may find future applications in thermoelectric
coolers, which are compact and vibration-free. The origin of its
large thermopower has been traced to electron spins which carry
a large fraction of the heat in an applied current. Surprisingly,
a magnetic field can suppress this spin-heat current by 100 percent
(figure). In addition, NaxCoO2 superconducts
when water is added. These exotic behaviors reflect the quantum
rules of how electrons hop in the material’s triangular lattice,
much like marbles in the popular board game 'Go.'
Related publication [DMR-0213706]:
Y. Wang, N.S. Rogado, R.J. Cava, N.P. Ong. "Spin Entropy As
the Likely Source of Enhanced Thermopower in NaXCo2O4,"
Nature 423, 425 (2003).
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