Complex Dirac-like Electronic Structure in Atomic Site Ordered Rh3In3.4Ge3.6

TL;DR

This study synthesizes a novel Rh3In3.4Ge3.6 compound with a complex Dirac-like electronic structure, revealing multiple Dirac nodes near the Fermi level, which could influence its electronic properties and potential applications.

Contribution

The paper reports the discovery and synthesis of a new Rh3In3.4Ge3.6 compound with a unique Dirac-like electronic structure, expanding understanding of Ir3Ge7-type materials.

Findings

Displays a complex Dirac-like electronic structure with multiple Dirac nodes.

Shows potential as a thermoelectric with a power factor of ~2 mW/cmK2 at 225 K.

Contains Dirac type-I, type-II, and type-III nodes near the Fermi level.

Abstract

We report the synthesis via an indium flux method of a novel single-crystalline compound Rh3In3.4Ge3.6 that belongs to the cubic Ir3Ge7 structure type. In Rh3In3.4Ge3.6, the In and Ge atoms choose to preferentially occupy, respectively, the 12d and 16f sites of the Im-3m space group, thus creating a colored version of the Ir3Ge7 structure. Like the other compounds of the Ir3Ge7 family, Rh3In3.4Ge3.6 shows potential as a thermoelectric displaying a relatively large power factor, PF ~ 2 mW/cmK2, at a temperature T ~ 225 K albeit showing a modest figure of merit, ZT = 8 x 10-4, due to the lack of a finite band gap. These figures might improve through a use of chemical substitution strategies to achieve band gap opening. Remarkably, electronic band structure calculations reveal that this compound displays a complex Dirac-like electronic structure relatively close to the Fermi level. The electronic structure is composed of several Dirac type-I and type-II nodes, and even Dirac type-III nodes that result from the touching between a flat band and a linearly dispersing band. This rich Dirac-like electronic dispersion offers the possibility to observe Dirac type-III nodes and study their role in the physical properties of Rh3In3.4Ge3.6 and related Ir3Ge7-type materials.