Quantum Charge Pumping in Helical Systems: Study Compares Short- and Long-Range Electron Hopping
Researchers used theoretical methods to study how electric charge can be pumped through helical structures when electrons can hop over varying distances. The study found that long-range hopping produces stable current plateaus at certain chemical potentials, while short-range hopping produces more variable currents sensitive to parameter changes. The findings could enable geometric control of quantum pumping in helical and chiral systems.
Using Keldysh non-equilibrium Green's function theory, physicists investigated charge pumping through single-stranded helical structures modeled with tight-binding theory, comparing scenarios where electrons can only hop between nearby sites versus over longer distances. The research reveals that long-range hopping creates pronounced plateau-like regions in the pumped direct current as a function of chemical potential when energy levels are sparsely spaced, consistent with adiabatic transport principles, whereas short-range hopping produces currents that vary more sensitively with parameters and lack clear plateaus. The stability of these plateaus depends on driving frequency: higher frequencies cause Floquet side-band mixing that destroys plateaus and generates oscillatory currents. A key finding is that the decay exponent in helical systems acts as an effective structural parameter that can tune both the magnitude and sign of pumped current, providing a geometric mechanism for controlling quantum pumping. The work addresses a previously unexplored gap in understanding spectral and pumped currents in helical geometries with extended hopping ranges.
What's missing
The study is theoretical and does not report experimental validation or discuss potential experimental implementations. The paper does not address possible applications beyond the stated relevance to chiral and quasi-one-dimensional systems, nor does it discuss computational complexity or scalability of the Keldysh approach for larger systems.
What different sources said
- arXiv physicsCenter
Quantum charge pumping in helical systems: A comparative study of short- and long-range hopping
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