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<p>Valleytronic applications utilize the valley degree of freedom—that is, the location of a state’s wavefunction within the Brillouin zone—to store and process information. In this context, the valley Hall effect is important for reading and writing the valley state. So far, research on this effect has focused on its linear response to an applied current and has not considered nonlinear responses. Here we report the observation of a nonlinear valley Hall effect in a graphene moiré superlattice, indicated by the generation of second-harmonic non-local voltages under a.c. currents. The nonlinear effect we observe has a magnitude surpassing the linear version and is highly tunable with a gate voltage. The nonlinear signal shows quadratic scaling with driving current and quartic scaling with local resistance, setting it apart from its linear counterpart. We further reveal a nonlinear inverse valley Hall effect by observing the third- and fourth-harmonic non-local voltages. This effect provides a mechanism for valley manipulation and may enable a valley rectifier device that converts a.c. charge current into d.c. valley current.</p>

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Observation of giant nonlinear valley Hall effect

  • 期刊论文

  • 发表日期：

    2026年3月31日

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  • Pan He,
  • Min Zhang,
  • Jin Cao,
  • Jingru Li,
  • Hao Liu,
  • Jinfeng Zhai,
  • Ruibo Wang,
  • Cong Xiao,
  • Shengyuan A. Yang,
  • Jian Shen

摘要

Valleytronic applications utilize the valley degree of freedom—that is, the location of a state’s wavefunction within the Brillouin zone—to store and process information. In this context, the valley Hall effect is important for reading and writing the valley state. So far, research on this effect has focused on its linear response to an applied current and has not considered nonlinear responses. Here we report the observation of a nonlinear valley Hall effect in a graphene moiré superlattice, indicated by the generation of second-harmonic non-local voltages under a.c. currents. The nonlinear effect we observe has a magnitude surpassing the linear version and is highly tunable with a gate voltage. The nonlinear signal shows quadratic scaling with driving current and quartic scaling with local resistance, setting it apart from its linear counterpart. We further reveal a nonlinear inverse valley Hall effect by observing the third- and fourth-harmonic non-local voltages. This effect provides a mechanism for valley manipulation and may enable a valley rectifier device that converts a.c. charge current into d.c. valley current.