Remarkable low-energy properties of the pseudogapped semimetal Be$_5$Pt

TL;DR

This study reveals that Be$_5$Pt exhibits remarkably stable electrical resistivity across temperatures due to a pseudogap and disorder effects, with properties tunable by pressure, highlighting its unique low-energy electronic behavior.

Contribution

The paper combines experimental measurements and theoretical calculations to uncover the pseudogapped semimetallic nature and low-energy properties of Be$_5$Pt, including the effects of disorder and pressure.

Findings

Resistivity remains nearly constant from low to room temperature.

A small true gap of about 3 meV exists at the Fermi level.

Pressure increases the band gap, making the material more semiconducting.

Abstract

We report measurements and calculations on the properties of the intermetallic compound Be$_5$Pt. High-quality polycrystalline samples show a nearly constant temperature dependence of the electrical resistivity over a wide temperature range. On the other hand, relativistic electronic structure calculations indicate the existence of a narrow pseudogap in the density of states arising from accidental approximate Dirac cones extremely close to the Fermi level. A small true gap of order 3 meV is present at the Fermi level, yet the measured resistivity is nearly constant from low to room temperature. We argue that this unexpected behavior can be understood by a cancellation of the energy dependence of density of states and relaxation time due to disorder, and discuss a model for electronic transport. With applied pressure, the resistivity becomes semiconducting, consistent with theoretical calculations that show that the band gap increases with applied pressure. We further discuss the role of Be inclusions in the samples.