Weak localization and small anomalous Hall conductivity in ferromagnetic Weyl semimetal Co₂TiGe

Area of Science:

• Condensed Matter Physics
• Materials Science
• Solid-State Physics

Background:

• Weyl semimetals are topological materials with potential applications in quantum computing and spintronics.
• Cobalt-based Heusler alloys are promising candidates for realizing Weyl semimetal properties due to time-reversal symmetry breaking.
• Co2TiGe is a predicted ferromagnetic Weyl semimetal, motivating experimental investigation.

Purpose of the Study:

• To experimentally verify the predicted Weyl semimetal behavior in Co2TiGe thin films.
• To investigate the transport properties, including weak localization and anomalous Hall effect, of Co2TiGe.
• To understand the temperature dependence of these phenomena and their underlying mechanisms.

Main Methods:

• Thin film growth of Co2TiGe using molecular beam epitaxy.
• Measurement of longitudinal resistivity and magnetoconductance as a function of temperature and magnetic field.
• Analysis of the anomalous Hall effect in the Co2TiGe thin films.

Main Results:

• Co2TiGe thin films exhibit semimetallic behavior in longitudinal resistivity.
• Weak localization quantum corrections were observed up to room temperature, with reduced dephasing length at lower temperatures.
• Negative longitudinal magnetoresistance was observed from 5 to 300 K, becoming positive at higher fields and temperatures.
• A small anomalous Hall conductivity was measured, decreasing with increasing temperature and potentially arising from intrinsic and extrinsic mechanisms.

Conclusions:

• The experimental results support the theoretical predictions of Co2TiGe as a ferromagnetic Weyl semimetal.
• Weak localization effects play a significant role in the transport properties of Co2TiGe thin films, even at room temperature.
• The observed anomalous Hall effect provides further evidence for the unique electronic structure of this material.