Project Details
Projekt
Study of the spin Nernst effect: absolute moments and dynamics
Subject Area
Experimental Condensed Matter Physics
Term
from 2014 to 2022
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 257600267
We propose to investigate and quantify the spin accumulation that is generated by heat currents (spin Nernst effect) in a material with finite spin-orbit interaction. The experiments will use two complementary approaches, one ultra-sensitive and one ultra-fast. In one set of experiments micro SQUID technology will be used to directly measure the absolute magnetic moments that are induced by the spin Nernst effect on the edges of a metallic bar. The bar is subjected to a thermal gradient which is either induced by resistive or by optical heating. With this ultra-sensitive technique (down to a few hundred electron spins) we plan to directly quantify the magnitude of the SNE. In addition, suitable design of the SQUID geometry will allow us to directly access the spin diffusion length. In close collaboration with theory this technique will be applied to various metals (Cu, Au) including doping by impurities in order to maximize the spin Nernst effect while separating intrinsic and extrinsic contributions. In a complementary set of experiments very large thermal gradients will be generated using an ultrafast pump-probe technique in order to study the dynamics of the spin Nernst effect. THz bow-tie antenna structures will be excited by 100 femtosecond single cycle THz-transients with a peak amplitude of 1 MV/cm. By proper design the THz-current in the antenna can be confined to a sub-micron sized dissipative shunt allowing for ultra-fast resistive heating. In this way we expect to reach thermal gradients in excess of 1 K/nm. These large temperature gradients will in turn drive heat currents in metallic structures with spin-orbit interaction where due to spin Nernst effect spin currents are generated. Simultaneously the time resolved magneto optic response will be used to study the dynamics of the corresponding spin polarization (with a spatial resolution of 200 nm). Since the heating pulses are applied on a sub-picosecond time scale these experiments allow a real time study of the time evolution and the decay of the spin accumulation generated by the spin Nernst effect.
DFG Programme
Priority Programmes
Subproject of
SPP 1538:
Spin Caloric Transport (SpinCaT)
