Direct measurement of broken time-reversal symmetry in centrosymmetric and non-centrosymmetric atomically thin crystals with nonlinear Kerr rotation

Abstract

Time-reversal symmetry, together with space-inversion symmetry, is one of the defining properties of crystals, underlying phenomena such as magnetism, topology and non-trivial spin textures. Transition metal dichalcogenides (TMDs) provide an excellent tunable model system to study the interplay between time-reversal and space-inversion symmetry, since both can be engineered on demand by tuning the number of layers and via all-optical bandgap modulation. In this work, we modulate and study time-reversal symmetry using third harmonic Kerr rotation in mono- and bilayer TMDs. By illuminating the samples with elliptically polarized light, we achieve spin-selective bandgap modulation and consequent breaking of time-reversal symmetry. The reduced symmetry modifies the nonlinear susceptibility tensor, causing a rotation of the emitted third harmonic polarization. With this method, we are able to probe broken time-reversal symmetry in both non-centrosymmetric (monolayer) and centrosymmetric (bilayer) crystals. Furthermore, we discuss how the detected third harmonic rotation angle directly links to the spin-valley locking in monolayer TMDs and to the spin-valley-layer locking in bilayer TMDs. Thus, our results define a powerful approach to study broken time-reversal symmetry in crystals regardless of space-inversion symmetry, and shed light on the spin, valley and layer coupling of atomically thin semiconductors.

Main: 24 pages, 5 figures, 48 references SI: 15 pages, 1 figure, 12 references

References in corpus (13)

• Ultrafast Generation of Pseudo-magnetic Field for Valley Excitons in WSe2 Monolayers
• Light-induced emergent phenomena in 2D materials and topological materials
• Linear and Nonlinear Optical constants of BiFeO_3
• All-optical polarization and amplitude modulation of second-harmonic generation in atomically thin semiconductors
• Light-Induced Valleytronics in Pristine Graphene
• Large, valley-exclusive Bloch-Siegert shift in monolayer WS2
• Lightwave-controlled band engineering in quantum materials
• Nonlinear co-generation of graphene plasmons for optoelectronic logic operations
• Parametric Nonlinear Optics with Layered Materials and Related Heterostructures
• Valley Polarization-Electric Dipole Interference and Nonlinear Chiral Selection Rules in Monolayer WSe${}_2$
• Electric quadrupole second harmonic generation revealing dual magnetic orders in a magnetic Weyl semimetal
• Ultrafast Opto-Electronic and Thermal Tuning of Third-Harmonic Generation in a Graphene Field Effect Transistor
• Impact of substrates and quantum effects on exciton line shapes of 2D semiconductors at room temperature