Supplementary material

Fig. S1. Calculated binding energies of the 1T-XA2(X = V, Nb, Ta; A = S, Se) /Cs3Bi2I9 heterostructures as the function of distance between 1T-2D metals and Cs3Bi2I9. Fig. S2. Calculated binding energies of the 1H-XA2/Cs3Bi2I9 heterostructures as the function of distance between 1H-2D metals and Cs3Bi2I9. Fig. S3. Projected band structures of the 1T-XA2/Cs3Bi2I9 heterostructures. Fig. S4. Projected band structures of the 1H-XA2/Cs3Bi2I9 heterostructures. Fig. S5. Projected band structures of 1T-NbSe2 and 1H-TaSe2 contact to Cs3Bi2I9 by applying external electric field from 0.1 to 0.4 V/Å. Fig. S6. Effective potentials of the 1T-XA2. Wm, Evacuum, and EFermi represent the work function, the vacuum energy, and the Fermi level energy, respectively. The red line represents the Fermi level. Fig. S7. Effective potentials of the 1H-XA2. The red line represents the Fermi level. Fig. S8. Band structures of the 1T-XA2. Fig. S9. Band structures of the 1H-XA2. Fig. S10. The projected density of states (PDOS) for the 1T-XA2/Cs3Bi2I9 heterostructures. The gray area represents the forbidden state of Cs3Bi2I9. Fig. S11. The projected density of states (PDOS) for the 1H-XA2/Cs3Bi2I9 heterostructures. The gray area represents the forbidden state of Cs3Bi2I9. Fig. S12. Planar charge density difference of the 1T-XA2/Cs3Bi2I9 heterostructures, where the red region represents electron accumulation, the blue region represents electron depletion, and the dashed line represents the interface region. Fig. S13. Planar charge density difference of the 1H-XA2/Cs3Bi2I9 heterostructures, where the red region represents electron accumulation, the blue region represents electron depletion, and the dashed line represents the interface region. Fig. S14. Effective potential distribution of the 1H-XA2/Cs3Bi2I9 heterostructures. The red line represents the Fermi level. Fig. S15. Effective potential distribution of the 1T-XA2/Cs3Bi2I9 heterostructures. The red line represents the Fermi level. Fig. S16. The calculated magnetic moment (blue triangles) and specific heat capacity (red dots) as functions of temperature for free-standing 1T/H-VA2(A=S,Se). Fig. S17. The calculated magnetic moment (blue triangles) and specific heat capacity (red dots) as functions of temperature for 1T/H-VA2/Cs3Bi2I9. Table S1: The detailed barrier height (ΦTB), barrier width (𝑑TB), and tunneling-specific resistance between Cs3Bi2I9 and 1H-XA2 contacts. Table S2: The detailed barrier height (ΦTB), barrier width (𝑑TB), and tunneling-specific resistance between Cs3Bi2I9 and 1T-XA2 contacts. Table S3: The detailed barrier height (ΦTB), barrier width (𝑑TB), and tunneling probability between Cs3Bi2I9 and 1H-XA2 contacts. Table S4: The detailed barrier height (ΦTB), barrier width (𝑑TB), and tunneling probability between Cs3Bi2I9 and 1T-XA2 contacts.