Speaker
Prof.
Heiner Linke
(Nanometer Structure Consortium, Lund University)
Description
Symmetry relationships such as the Onsager relations, which
are based on the principle of microreversibility, are
cornerstones of physics. In the context of mesoscopic
physics, symmetries of the conductance in two-terminal and
multiterminal devices have been explored in great detail
[1,2,3]. Here, we extend these studies to the case where
combined thermal and electric (thermoelectric) biases are
present. Also for this case, symmetry relations have been
predicted, but it has also been predicted that these
relations break down at the transition from quantum to
classical behavior. An experimental test is therefore
necessary. We have experimentally investigated the magnetic
field dependence of thermoelectric transport properties in a
four-terminal micro-junction, with heat and voltage
reservoirs attached to each terminal [4,5]. The linear
response thermoelectric coefficients are found to be
symmetric under a simultaneous reversal of magnetic field
and exchange of injection and emission terminals, confirming
the generality of the magnetic-field symmetries. In the
non-linear thermal bias regime we find signatures of a
break-down of the symmetries, raising new fundamental
questions about the mechanism of this breakdown.
References
[1] Büttiker, M., Symmetry of electrical conduction. IBM J.
Res. Developm., 32(3), 317 (1988).
[2] Löfgren, A., Marlow, C., Shorubalko, I., Taylor, R.,
Omling, P., Samuelson, L., & Linke, H., Symmetry of
two-terminal nonlinear electric conduction. Physical Review
Letters, 92(4), 046803 (2004).
[3] Marlow, C., Taylor, R., Fairbanks, M., Shorubalko, I., &
Linke, H., Experimental investigation of the breakdown of
the Onsager-Casimir relations. Physical Review Letters,
96(11), 116801 (2006).
[4] Matthews, J., Sánchez, D., Larsson, M., & Linke, H.,
Thermally driven ballistic rectifier. Physical Review B,
85(20), 205309 (2012)
[5] J. Matthews et al., to be submitted (2013).
