Manifestations of fine features of the density of states in the transport properties of KOs2O6

TL;DR

This study investigates how high-pressure conditions affect the transport properties of KOs2O6, revealing unconventional behaviors linked to the density of states near the Fermi energy, with implications for understanding its superconductivity.

Contribution

It provides a detailed analysis of the influence of pressure on the transport properties of KOs2O6 using a simple band model centered on the density of states near EF.

Findings

Resistivity does not saturate at low temperatures.

Thermoelectric power shows nonmetallic behavior up to 700 K.

Pressure mainly affects low-energy electronic excitations.

Abstract

We performed high-pressure transport measurements on high-quality single crystals of KOs2O6, a beta-pyrochlore superconductor. While the resistivity at high temperatures might approach saturation, there is no sign of saturation at low temperatures, down to the superconducting phase. The anomalous resistivity is accompanied by a nonmetallic behavior in the thermoelectric power (TEP) up to temperatures of at least 700 K, which also exhibits a broad hump with a maximum at 60 K. The pressure influences mostly the low-energy electronic excitations. A simple band model based on enhanced density of states in a narrow window around the Fermi energy (EF) explains the main features of this unconventional behavior in the transport coefficients and its evolution under pressure.