Quantum transport and spintronics in topological semimetal heterostructures

We provide an overview of the synthesis and study of epitaxially grown topological semimetal heterostructures, focusing on Dirac semimetals (Cd₃As₂, ZrTe₂) and Weyl semimetals (TaAs, NbAs). Studies of the integer quantum Hall effect in high mobility films of Cd₃As₂provide new insights into the effects of quantum confinement on the g-factor of Dirac states [1]. By interfacing Cd₃As₂ and TaAs with a ferromagnetic metal (Ni_0.8Fe_0.2), we probe efficient spin-charge conversion at room temperature, in agreement with first principles calculations of the spin hall conductivity [2,3]. We also observe suprising effects of an interfacial oxide on the magnitude and sign of the spin-charge conversion efficiency. Finally, we discuss the spin-charge conversion and spin orbit torque in ZrTe₂/CrTe₂ heterostructures wherein a Dirac semimetal is interfaced with a 2D ferromagnet [4].<br/><br/>This work is sponsored in part by SMART, a funded center of nCORE, a Semiconductor Research Corporation (SRC) program sponsored by NIST, the Institute for Quantum Matter under DOE EFRC grant DE-SC0019331, and the Penn State Two-Dimensional Crystal Consortium-Materials Innovation Platform (2DCC-MIP) under NSF Grant No. DMR- 2039351.<br/><br/><br/>1. R. Xiao <i>et al., </i>"Integer quantum Hall effect and enhanced g factor in quantum-confined Cd₃As₂ films," <i>Physical Review B </i><b>106</b>, L201101 (2022). <br/>2. W. Yanez <i>et al</i>., “Spin and charge interconversion in Dirac semimetal thin films,” <i>Physical Review Applied </i><b>16</b>, 054031 (2021). <br/>3. W. Yanez <i>et al</i>., “Giant dampinglike-torque efficiency in naturally oxidized polycrystalline TaAs thin films,” <i>Physical Review Applied </i><b>18</b>, 054004 (2022). <br/>4. Y. Ou <i>et al</i>., “ZrTe₂/CrTe₂: an epitaxial van der Waals platform for spintronics,” <i>Nature Communications </i><b>13</b>, 2972 (2022).