TY - JOUR

T1 - Quantum thermopower of metallic atomic-size contacts at room temperature

AU - Evangeli, Charalambos

AU - Matt, Manuel

AU - Rincón-García,, Laura

AU - Pauly, Fabian

AU - Nielaba, Peter

AU - Rubio-Bollinger, Gabino

AU - Cuevas, Juan Carlos

AU - Agrait, Nicolas

PY - 2015/2/11

Y1 - 2015/2/11

N2 - We report conductance and thermopower measurements of metallic atomic-size contacts, namely gold and platinum, using a scanning tunneling microscope (STM) at room temperature. We find that few-atom gold contacts have an average negative thermopower, whereas platinum contacts present a positive thermopower, showing that for both metals, the sign of the thermopower in the nanoscale differs from that of bulk wires. We also find that the magnitude of the thermopower exhibits minima at the maxima of the conductance histogram in the case of gold nanocontacts while for platinum it presents large fluctuations. Tight-binding calculations and Green’s function techniques, together with molecular dynamics simulations, show that these observations can be understood in the context of the Landauer–Büttiker picture of coherent transport in atomic-scale wires. In particular, we show that the differences in the thermopower between these two metals are due to the fact that the elastic transport is dominated by the 6s orbitals in the case of gold and by the 5d orbitals in the case of platinum.

AB - We report conductance and thermopower measurements of metallic atomic-size contacts, namely gold and platinum, using a scanning tunneling microscope (STM) at room temperature. We find that few-atom gold contacts have an average negative thermopower, whereas platinum contacts present a positive thermopower, showing that for both metals, the sign of the thermopower in the nanoscale differs from that of bulk wires. We also find that the magnitude of the thermopower exhibits minima at the maxima of the conductance histogram in the case of gold nanocontacts while for platinum it presents large fluctuations. Tight-binding calculations and Green’s function techniques, together with molecular dynamics simulations, show that these observations can be understood in the context of the Landauer–Büttiker picture of coherent transport in atomic-scale wires. In particular, we show that the differences in the thermopower between these two metals are due to the fact that the elastic transport is dominated by the 6s orbitals in the case of gold and by the 5d orbitals in the case of platinum.

KW - Quantum thermopower

KW - quantum conductance

KW - atomic-size metallic contacts

KW - Landauer approach

KW - molecular dynamics simulations

U2 - 10.1021/nl503853v

DO - 10.1021/nl503853v

M3 - Letter

VL - 15

SP - 1006

EP - 1011

JO - Nano Letters

JF - Nano Letters

SN - 1530-6984

IS - 2

ER -