Konstantin Denisov (University at Buffalo)

Date: Mon. November 24th, 2025, 12:45 pm-1:45 pm
Location: Rockefeller 221 (Foldy Room) & Zoom
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Proximity-induced phenomena in two-dimensional Dirac materials:
From topological kink states to a spin-charge interconversion

Dr. Konstantin Denisov

Department of Physics, University at Buffalo

(Host: Shulei Zhang)

Abstract: Atomically thin character of a two-dimensional (2D) material ensures that it is significantly influenced by neighbors, thereby resulting in strong proximity effects [1]: A situation when a 2D material acquires properties absent in a pristine state, such as superconductivity, magnetism, topological structure or an enhanced spin-orbit coupling (SOC). Two-dimensional (2D) Dirac materials host the electron Dirac points with gapless linear dispersion close to the Fermi energy and are actively being studied for its nontrivial behavior. In this talk I’m going to discuss several prominent phenomena realized in 2D Dirac systems with strong proximity effects.

Unlike in the 3D case, the protection of Dirac gapless points in 2D is not robust [2]: In the absence of this protection, the gap opening favors topological effects induced by the generation of a finite Berry curvature. In our work [3], we have combined this with Dirac points detached from high symmetry points of the Brillouin zone and have studied topological phenomena emerging in 2D materials with movable Dirac points that can be further controlled by ferroelectrics (FEs). I will discuss topology-enforced kink electronic states at structural domain walls separating opposite FE polarizations and also show that the position of movable Dirac points modifies the dipole character of the Berry curvature, responsible for switching between the zero and nonzero second-harmonic nonlinear Hall conductivity. These predictions can be realized in a wide range of identified 2D materials, which is supported by first-principles analysis of Cl₂Rh₂S₂-GeS junction.

Furthermore, a monolayer graphene, the most remarkable example of a 2D material with Dirac points, with proximity effects from either magnetic, antiferromagnetic or heavy element-based materials gets an enhanced SOC, which promotes the spin-charge interconversion (SCI) [4]. I will discuss how the SCI emerging from spin-pseudospin proximity terms in the Dirac Hamiltonian manifests itself for ac-electrical driving across different frequencies: From terahertz range, where the spin-flip absorption features strong enhancement and anomalous polarization structure [5], to mid-infrared range, where SOC-proximity gives rise to a fine structure of cyclotron resonances, and up to visible range where it leads to the remarkable mixing of s- and p- excitons with a strong brightening of spin-forbidden p-excitons in the absorption spectrum [6].

 

References

[1] I. Žutić et al., “Proximitized materials”, Materials Today, 22, 85 (2019).

[2] S. M. Young and C. L. Kane, Phys. Rev. Lett. 115, 126803 (2015).

[3] K. S. Denisov, Y. Liu and I. Žutić, Phys. Rev. Lett. 134, 246602 (2025).

[4] J. F. Sierra et al., Nat. Nanotechnol. 16, 856 (2021).

[5] K. S. Denisov, I.V. Rozhansky, S.O. Valenzuela and I. Žutić, Phys. Rev. B., 109, L201406 (2024).

[6] D. J. Cao, K. S. Denisov and I. Žutić, Phys. Rev. B., 112, L161405 (2025).