Tunable spin-charge conversion in class-I topological Dirac semimetals

• Published in: arXiv.org
• Main Authors: Rui-Hao, Li, Shen, Pengtao, Zhang, Steven S -L
• Format: Paper Journal Article
• Language: English
• Published: Ithaca Cornell University Library, arXiv.org 13.04.2022
• Subjects: Charge reversal; Conversion; Electric currents; Electric fields; Electrons; Hall effect; Magnetic fields; Mathematical analysis; Metalloids; Physics - Materials Science; Physics - Mesoscale and Nanoscale Physics; Spintronics; Symmetry; Tensors; Topology
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.2110.11823

We theoretically demonstrate that class-I topological Dirac semimetals (TDSMs) can provide a platform for realizing both electrically and magnetically tunable spin-charge conversion. With time-reversal symmetry, the spin component along the uniaxial rotation axis (\(z\)-axis) is approximately conserved, which leads to an anisotropic spin Hall effect -- the resulting spin Hall current relies on the relative orientation between the external electric field and the \(z\)-axis. The application of a magnetic field, on the other hand, breaks time-reversal symmetry, driving the TDSM into a Weyl semimetal phase and, consequently, partially converting the spin current to a charge Hall current. Using the Kubo formulas, we numerically evaluate the spin and charge Hall conductivities based on a low-energy TDSM Hamiltonian together with the Zeeman coupling. Besides the conventional tensor element of the spin Hall conductivity \(\sigma_{xy}^z\), we find that unconventional components, such as \(\sigma_{xy}^x\) and \(\sigma_{xy}^y\), also exist and vary as the magnetic field is rotated. Likewise, the charge Hall conductivity also exhibits appreciable tunability upon variation of the magnetic field. We show that such tunability -- as well as large spin-charge conversion efficiency -- arises from the interplay of symmetry and band topology of the TDSMs.