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Optical control of the valley Zeeman effect through many-exciton interactions


Charge carriers in two-dimensional transition metal dichalcogenides (TMDs), such as WSe2, have their spin and valley-pseudospin locked into an optically addressable index that is proposed as a basis for future information processing1,2. The manipulation of this spin–valley index, which carries a magnetic moment3, requires tuning its energy. This is typically achieved through an external magnetic field (B), which is practically cumbersome. However, the valley-contrasting optical Stark effect achieves valley control without B, but requires large incident powers4,5. Thus, other efficient routes to control the spin–valley index are desirable. Here we show that many-body interactions among interlayer excitons (IXs) in a WSe2/MoSe2 heterobilayer (HBL) induce a steady-state valley Zeeman splitting that corresponds to B ≈ 6 T. This anomalous splitting, present at incident powers as low as microwatts, increases with power and is able to enhance, suppress or even flip the sign of a B-induced splitting. Moreover, the g-factor of valley Zeeman splitting can be tuned by ~30% with incident power. In addition to valleytronics, our results could prove helpful to achieve optical non-reciprocity using two-dimensional materials.

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Fig. 1: Many-exciton exchange interactions among IXs with a WSe2/MoSe2 heterostructure.
Fig. 2: Exchange field-induced splitting in WSe2/MoSe2 heterostructure.
Fig. 3: Equivalence between the exchange field and the external magnetic field.
Fig. 4: Non-linear behaviour of Zeeman splitting under a large circular excitation power.

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Data availability

The authors declare that the data supporting the findings of this study are available within the paper, Supplementary Information and Source Data. Extra data are available from the corresponding authors upon request. Source data are provided with this paper.


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We acknowledge many enlightening discussions with A. Imamoğlu. A.S. acknowledges support from the NSF through the EFRI program, grant no. EFMA-1741691, and from NSF DMR award no. 1905809.

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Authors and Affiliations



W.L., X.L. and J.W. contributed equally to this work. A.S., W.L. and X.L. conceived the project. W.L., X.L. and J.W. carried out the measurements. J.W. prepared the samples. A.S. supervised the project. All the authors were involved in the analysis of the experimental data and contributed extensively to this work.

Corresponding author

Correspondence to Ajit Srivastava.

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The authors declare no competing interests.

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Nature Nanotechnology thanks the anonymous reviewers for their contribution to the peer review of this work.

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Supplementary information

Supplementary Information

Supplementary Notes 1–7 and Figs. 1–14.

Source data

Source Data Fig. 1

Numerical data used to generate graphs in Fig. 1.

Source Data Fig. 2

Numerical data used to generate graphs in Fig. 2.

Source Data Fig. 3

Numerical data used to generate graphs in Fig. 3.

Source Data Fig. 4

Numerical data used to generate graphs in Fig. 4.

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Li, W., Lu, X., Wu, J. et al. Optical control of the valley Zeeman effect through many-exciton interactions. Nat. Nanotechnol. 16, 148–152 (2021).

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