Controlling the Entropy of a Single-Molecule Junction
Eugenia Pyurbeeva (Queen Mary University of London)
C. Hsu (Kavli institute of nanoscience Delft, TU Delft - QN/van der Zant Lab)
David Vogel (University of Basel)
Christina Wegeberg (University of Basel)
Marcel Mayor (Sun Yat-sen University, University of Basel)
H.S.J. van der Zant (TU Delft - QN/van der Zant Lab, Kavli institute of nanoscience Delft)
Jan A. Mol (Queen Mary University of London)
P. Gehring (Université Catholique de Louvain)
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Abstract
Single molecules are nanoscale thermodynamic systems with few degrees of freedom. Thus, the knowledge of their entropy can reveal the presence of microscopic electron transfer dynamics that are difficult to observe otherwise. Here, we apply thermocurrent spectroscopy to directly measure the entropy of a single free radical molecule in a magnetic field. Our results allow us to uncover the presence of a singlet to triplet transition in one of the redox states of the molecule, not detected by conventional charge transport measurements. This highlights the power of thermoelectric measurements which can be used to determine the difference in configurational entropy between the redox states of a nanoscale system involved in conductance without any prior assumptions about its structure or microscopic dynamics.