Anomalous Landau Level Gaps Near Magnetic Transitions in Monolayer <math display=

Benjamin A. Foutty; Vladimir Calvera; Zhaoyu Han; Carlos R. Kometter; Song Liu; Kenji Watanabe; Takashi Taniguchi; James C. Hone; Steven A. Kivelson; Benjamin E. Feldman

doi:10.1103/physrevx.14.031018

Article Anomalous Landau Level Gaps Near Magnetic Transitions in Monolayer

{WSe}_{2}

Benjamin A. Foutty ; Vladimir Calvera ; Zhaoyu Han ; Carlos R. Kometter ; Song Liu ; Kenji Watanabe ; Takashi Taniguchi ; James C. Hone ; Steven A. Kivelson ; Benjamin E. Feldman

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Benjamin A. Foutty, Vladimir Calvera, Zhaoyu Han, Carlos R. Kometter, Song Liu, Kenji Watanabe, Takashi Taniguchi, James C. Hone, Steven A. Kivelson, Benjamin E. Feldman. Anomalous Landau Level Gaps Near Magnetic Transitions in Monolayer

{WSe}_{2}

. Physical Review X. 2024, 14 (3), 031018. https://doi.org/10.1103/physrevx.14.031018

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First-order phase transitions produce abrupt changes to the character of both ground and excited electronic states. Here we conduct electronic compressibility measurements to map the spin phase diagram and Landau level (LL) energies of monolayer WSe2 in a magnetic field. We resolve a sequence of first- order phase transitions between completely spin-polarized LLs and states with LLs of both spins. Unexpectedly, the LL gaps are roughly constant over a wide range of magnetic fields below the transitions, which we show reflects spin-polarized ground states with opposite spin excitations. These transitions also extend into compressible regimes, with a sawtooth boundary between full and partial spin polarization. We link these observations to the important influence of LL filling on the exchange energy beyond a smooth density-dependent contribution. Our results show that WSe2 realizes a unique hierarchy of energy scales where such effects induce reentrant magnetic phase transitions tuned by density and magnetic field.

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