Fig. 1: Concept and demonstration of spin accumulation measurements on MoTe₂ flakes.

a Left panel: crystal structure of T_d-MoTe₂. Middle panel: schematic of the device and measurement setup. Purple and cyan flakes represent MoTe₂ and blocking h-BN, respectively. Gray and gold electrodes represent Ni and Au, respectively. The charge current is applied along the MoTe₂ a-axis and the magnetic field can be applied along any direction within the ab-plane to polarize the Ni. The voltage measured between the Ni and Au Hall leads senses the spin-dependent electrochemical potential locally in MoTe₂ at the Ni contact position. A difference is detected for current-induced spin polarization aligned or anti-aligned with the Ni polarization. Right panel: optical image of example MoTe₂ device with Ni contact to the MoTe₂ “bulk”. The MoTe₂ flake and blocking h-BN are outlined by purple and cyan dashed line. The Ni electrode is colorized with gray for convenience. b Representative spin accumulation results taken at 2 K for Device 1 (20 nm). Left panel: background-subtracted spin-dependent electrochemical potential V as a function of magnetic field B (\(\theta=-{22}^{\circ }\)) for various positive currents (I = 0.3, 0.6, 1 mA). A “positive” hysteresis loop is seen due to the change of the magnetization state of the Ni relative to the local MoTe₂ spin polarization. The height of the hysteresis scales with current. The upper left inset shows the extracted hysteresis voltage ΔV (defined in the main panel) vs. current, indicating a linear relationship. Right panel: V vs. B for negative current flow (I = −1 mA) exhibits a “negative” hysteresis loop.