Pressure dependence of the thermoelectric power of single-walled carbon nanotubes

TL;DR

This study investigates how hydrostatic pressure influences the thermoelectric power of single-walled carbon nanotubes across a range of temperatures, revealing pressure-dependent enhancements linked to phonon population changes.

Contribution

It provides the first detailed analysis of pressure effects on thermoelectric power in single-walled carbon nanotubes over a broad temperature range.

Findings

Thermoelectric power increases monotonically with temperature at all pressures.

Low-temperature thermoelectric power is pressure independent, indicating metallic behavior.

Higher temperatures show pressure-dependent enhancement related to phonon population changes.

Abstract

We have measured the thermoelectric power (S) of high purity single-walled carbon nanotube mats as a function of temperature at various hydrostatic pressures up to 2.0 GPa. The thermoelectric power is positive, and it increases in a monotonic way with increasing temperature for all pressures. The low temperature (T < 40 K) linear thermoelectric power is pressure independent and is characteristic for metallic nanotubes. At higher temperatures it is enhanced and though S(T) is linear again above about 100 K it has a nonzero intercept. This enhancement is strongly pressure dependent and is related to the change of the phonon population with hydrostatic pressure.