Quantum Charge Pumping in Helical Systems: Study Compares Short- and Long-Range Electron Hopping
Researchers used the Keldysh non-equilibrium Green's function approach to investigate quantum charge pumping through single-stranded helical structures, comparing short-range and long-range electron hopping models. Long-range hopping was found to produce stable plateau-like regions in pumped dc current as a function of chemical potential, consistent with adiabatic transport, while short-range hopping yielded more parameter-sensitive, plateau-free behavior. The findings offer a geometric mechanism — via the decay exponent of long-range hopping — for tuning both the magnitude and sign of pumped current in helical and other chiral quasi-one-dimensional systems.
A new preprint posted to arXiv investigates quantum charge pumping in single-stranded helical tight-binding structures, comparing the behavior of short-range hopping (SRH) and long-range hopping (LRH) under time-periodic end potentials. Using the Keldysh non-equilibrium Green's function formalism, the authors analyze both energy-resolved spectral currents and dc pumped currents. A key finding is that LRH produces pronounced plateau-like regions in the dc pumped current as a function of chemical potential when energy levels are sparsely spaced, a signature of adiabatic transport, whereas SRH does not exhibit such plateaus. These plateaus are sensitive to drive frequency: at higher frequencies, Floquet side-band mixing disrupts the plateau structure and introduces oscillatory behavior. The phase dependence of the pumped current is nearly sinusoidal in both cases, and the current vanishes at zero phase lag, confirming that out-of-phase driving potentials are necessary for net pumping. Importantly, the decay exponent governing long-range hopping acts as an effective structural parameter capable of tuning both the magnitude and sign of the pumped current, providing a geometric knob for controlling quantum transport. The authors suggest these results can be extended to other chiral or quasi-one-dimensional systems beyond the helical geometry studied here.
What's missing
The study is a theoretical preprint and has not yet undergone peer review. It does not address experimental realizability or specific material platforms where these helical tight-binding models could be implemented. The robustness of the plateau features to disorder, decoherence, or finite-temperature effects is not discussed.
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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