Researchers have discovered time-reversal symmetry breaking in an altermagnetic material called manganese telluride, a finding that reshapes understanding of how spins behave in nearly non-magnetic systems.
Time-reversal symmetry describes physics that appears different when time flows backward versus forward. Scientists have long sought this exotic property in systems with minimal overall magnetization, since such phases promise advantages for spintronics, the technology that encodes information using electron spins rather than charge alone.
The team observed that applying mechanical strain to manganese telluride flipped the Hall signal, a measure of how charge carriers respond to magnetic fields. This flip reveals the underlying time-reversal symmetry breaking in the altermagnetic structure. Altermagnets form a special class of magnetic materials where opposing spin sublattices cancel each other's magnetic moments, producing near-zero net magnetization while retaining spin asymmetry.
The significance lies in practical application. Traditional ferromagnetic materials used in spintronics require strong magnetic fields or permanent magnetization, which consume power and complicate device design. Altermagnets offer the same spin-dependent physics without these drawbacks. By demonstrating tunable control through strain, researchers have shown a mechanism to engineer spintronic devices with greater efficiency.
The Hall signal reversal indicates the researchers can manipulate the fundamental electronic structure through mechanical stress, a technique already compatible with semiconductor manufacturing. This compatibility removes barriers to integration with existing technology.
The work bridges theory and experiment. Physicists predicted time-reversal symmetry breaking in altermagnets years ago, but observing it in a material simple enough for practical use represents progress. Manganese telluride's crystal structure allows researchers to apply strain systematically while monitoring electronic response.
Limitations remain. Laboratory demonstrations must scale to functional devices. The team tested the effect under specific conditions; performance at room temperature