Anomalous spin Nernst effect in Weyl semimetals

Area of Science:

• Condensed Matter Physics
• Spintronics
• Materials Science

Background:

• The spin Nernst effect generates a transverse spin current from a longitudinal thermal gradient in materials with spin-orbit coupling.
• Weyl semimetals are topological materials exhibiting unique electronic properties.
• Understanding spin transport phenomena in Weyl semimetals is crucial for next-generation spintronic devices.

Purpose of the Study:

• To investigate the spin Nernst effect in a mesoscopic four-terminal cross-bar Weyl semimetal device.
• To analyze the behavior of spin currents and coefficients under a perpendicular magnetic field.
• To explore the influence of symmetries and device geometry on the spin Nernst effect.

Main Methods:

• Utilized a tight-binding Hamiltonian model.
• Employed the nonequilibrium Green's function method for calculations.
• Simulated a four-terminal cross-bar Weyl semimetal device geometry.
• Analyzed three distinct connection modes (x-z, z-x, x-y).

Main Results:

• Observed an anomalous spin Nernst effect in Weyl semimetals, differing from traditional effects.
• A z-direction spin current emerges only under a magnetic field.
• Transverse spin currents in x and y directions exhibit in-phase behavior.
• Spin Nernst coefficients show strong anisotropy dependent on thermal gradient and lead connection.
• Symmetries of Weyl semimetals dictate the energy and magnetic field dependence of coefficients.

Conclusions:

• The observed anomalous spin Nernst effect in Weyl semimetals offers a new avenue for spintronic applications.
• The strong anisotropy and unique magnetic field dependence provide a method for characterizing magnetic Weyl semimetals.
• This study highlights the potential of Weyl semimetals in advanced electronic and spintronic devices.