Experimental signature of the attractive Coulomb force between between positive and negative magnetic monopoles in spin ice

Orateur : Carley PAULSEN (Magnétisme et Supraconductivité)

Thermal physics, electrical engineering, chemistry and biochemistry are essentially determined by the Coulomb interaction of quasiparticles. Such quasiparticles are not real and cannot be interrogated by the methods of particle physics. So how do you prove experimentally that two quasiparticles interact via Coulomb’s law ? In this talk I will show how this can be done for magnetic, rather than electric quasiparticles. By freezing spin ice to 65 mK we create (+-) pairs of emergent magnetic monopoles which we then separate with a magnetic field. Our experiment is arranged to make the magnetic current exactly analogous to an electrical current, and we observe a current that grows exponentially with the square root of the applied field. A non-Ohmic current that grows exponentially with the square root of applied electric field is well known from thermionic emission, electrolytes and semiconductors. It is a universal signature of the attractive Coulomb force between positive and negative electrical charges, which is revealed as the charges are driven in opposite directions by the force of an applied electric field.

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