Type-II quantum spin Hall effect in two-dimensional metals

Area of Science:

• Condensed matter physics
• Quantum mechanics
• Materials science

Background:

• The quantum spin Hall (QSH) effect is typically observed in topological insulators and quantum wells.
• Observation of the QSH effect in metals remains elusive.
• Previous methods relied on specific material properties or configurations.

Purpose of the Study:

• To propose and theoretically analyze an experiment for observing the Type-II QSH effect in a two-dimensional (2D) metal.
• To utilize a novel, relativistically gauge-invariant 2D QSH Hamiltonian.
• To generate and measure spontaneously quantized spin currents in a spin-unpolarized 2D metal.

Main Methods:

• An experiment involving a 2D metallic Corbino disk subjected to an azimuthal vector potential and a radial electric field is proposed.
• A cylindrical solenoid generates the vector potential without a magnetic field within the disk.
• Quantized azimuthal charge and spin currents are generated by combined changes in current and applied fields.

Main Results:

• The quantum Hamiltonians for the proposed experiments are solved exactly.
• The generation of spontaneously quantized azimuthal charge and spin currents is demonstrated.
• A method to control Joule heating is presented, suggesting potential for room-temperature measurements.

Conclusions:

• The proposed experiment offers a new pathway to observe the Type-II QSH effect in metals.
• This work provides a theoretical framework and experimental design for detecting quantized spin currents.
• The findings could pave the way for novel spintronic devices operating at room temperature.