Gate-tunable giant negative magnetoresistance in tellurene driven by quantum geometry.

Abstract

Negative magnetoresistance in conventional two-dimensional electron gases is a well known phenomenon, but its origin in complex and topological materials endowed with nontrivial quantum geometry remains elusive. Here, we report a giant negative magnetoresistance reaching  -90% of the zero-field resistance, R₀, in n-type tellurene films. The effect persists up to 35 T at cryogenic temperatures and is suppressed when the chemical potential moves away from the conduction-band Weyl node, suggesting a quantum geometric origin. We propose two mechanisms: quantum geometric enhancement of diffusion and a magnetoelectric spin interaction that locks the spin of a cyclotron-moving Weyl fermion, in the presence of an intrinsic inversion-breaking polar field <math xmlns="http://www.w3.org/1998/Math/MathML"><mi>E</mi></math> and an applied magnetic field B, to its guiding-center drift, <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><mo>(</mo><mrow><mi>E</mi><mo>×</mo><mi>B</mi></mrow><mo>)</mo></mrow><mo>⋅</mo><mi>σ</mi></math>. The resulting diffusion enhancement yields <math xmlns="http://www.w3.org/1998/Math/MathML"><mi>Δ</mi><msub><mrow><mi>R</mi></mrow><mrow><mi>z</mi><mi>z</mi></mrow></msub><mo>/</mo><msub><mrow><mi>R</mi></mrow><mrow><mn>0</mn></mrow></msub><mo>=</mo><mo>-</mo><msub><mrow><mi>β</mi></mrow><mrow><mi>g</mi></mrow></msub><msup><mrow><mrow><mo>(</mo><mrow><mi>E</mi><mo>×</mo><mi>B</mi></mrow><mo>)</mo></mrow></mrow><mrow><mn>2</mn></mrow></msup></math>, with β_g set by the quantum metric. Our findings establish a quantum geometric, non-Markovian memory effect in magnetotransport.