Large antiferromagnetic fluctuation enhancement of the thermopower at a critical doping in magnetic semimetal Cr1+dTe2

TL;DR

This study reveals that in Cr1+dTe2, antiferromagnetic fluctuations near a critical doping level significantly enhance thermopower, linking magnetic fluctuations with improved thermoelectric performance.

Contribution

It demonstrates the doping-dependent sign change and enhancement of thermopower linked to magnetic fluctuations and band structure evolution in Cr1+dTe2.

Findings

Thermopower sign changes at critical doping d~0.5.

Enhanced thermoelectric response near the critical doping.

Antiferromagnetic fluctuations correlate with thermopower enhancement.

Abstract

Cr1+dTe2 is a self-intercalated transition metal dichalcogenide that hosts tunable electronic filling and magnetism in its semimetallic band structure. Recent angle-resolved photoemission spectroscopy (ARPES) studies have unveiled a systematic shift in this semimetallic band structure relative to the chemical potential with increased Cr doping. This report presents the temperature and magnetic field dependence of the longitudinal thermopower Sxx for different Cr1+dTe2 compositions. We show that as doping increases, the sign of Sxx changes from positive to negative at the critical doping level of d ~ 0.5. This observed doping-dependent trend in the thermopower is consistent with the evolution of the semimetallic band structure from ARPES. Importantly, an anomalous enhancement of the thermoelectric response is also observed around d~0.5. Combining information from magnetometry and ARPES measurements, existence of the critical nature of the doping level dc (~0.5) is unveiled in magnetic semimetal Cr1+dTe2, where antiferromagnetic fluctuation and near-Fermi-energy pseudogap formation play a potential vital role in enhancing thermoelectric energy conversion.