Floquet spin states in OLEDs

Abstract

Weakly spin-orbit coupled electron and hole spins in organic light-emitting diodes (OLEDs) constitute near-perfect two-level systems to explore the interaction of light and matter in the ultrastrong-drive regime. Under such highly non-perturbative conditions, the frequency at which the spin oscillates between states, the Rabi frequency, becomes comparable to its natural resonance frequency, the Larmor frequency. For such conditions, we develop an intuitive understanding of the emergence of hybrid light-matter states, illustrating how dipole-forbidden multiple-quantum transitions at integer and fractional g-factors arise. A rigorous theoretical treatment of the phenomena comes from a Floquet-style solution to the time-dependent Hamiltonian of the electron-hole spin pair under resonant drive. To probe these phenomena experimentally requires both the development of a magnetic-resonance setup capable of supporting oscillating driving fields comparable in magnitude to the static field defining the Zeeman splitting; and an organic semiconductor which is characterized by minimal inhomogeneous broadening so as to allow the non-linear light-matter interactions to be resolved. The predicted exotic resonance features associated with the Floquet states are indeed found experimentally in measurements of spin-dependent steady-state OLED current under resonant drive, demonstrating that complex hybrid light-matter spin excitations can be formed and probed at room temperature. The spin-Dicke state arising under strong drive is insensitive to power broadening so that the Bloch-Siegert shift of the resonance becomes apparent, implying long coherence times of the dressed spin state with potential applicability for quantum sensing.

arXiv commentManuscript: 26 pages, 3 figures; supplementary information: 28 pages, 7 figures

References in corpus (15)

• The nitrogen-vacancy colour centre in diamond
• Beyond the Jaynes-Cummings model: circuit QED in the ultrastrong coupling regime
• Observation of Floquet-Bloch states on the surface of a topological insulator
• Ultrastrong coupling regimes of light-matter interaction
• Observation of the Bloch-Siegert Shift in a Qubit-Oscillator System in the Ultrastrong Coupling Regime
• Ultrastrong coupling of the cyclotron transition of a two-dimensional electron gas to a THz metamaterial
• Large, valley-exclusive Bloch-Siegert shift in monolayer WS2
• Extremely Nonperturbative Nonlinearities in GaAs Driven by Atomically Strong Terahertz Fields in Gold Metamaterials
• Revealing weak spin-orbit coupling effects on charge carriers in a $\pi$-conjugated polymer
• OLEDs as models for bird magnetoception: detecting electron spin resonance in geomagnetic fields
• Organic magnetoresistance under resonant ac drive
• Perdeuteration of poly[2-methoxy-5-(2'-ethylhexyloxy)-1,4-phenylenevinylene] (d-MEHPPV): control of microscopic charge-carrier spin-spin coupling and of magnetic-field effects in optoelectronic devices
• Floquet theory of radical pairs in radiofrequency magnetic fields
• Comparative analysis of magnetic resonance in the polaron pair recombination and the triplet exciton-polaron quenching models
• Real Time Electrical Detection of Coherent Spin Oscillations

Cited by in corpus (6)

• Steady Floquet-Andreev States Probed by Tunnelling Spectroscopy
• Line Shapes of Electric Dipole Spin Resonance in Pauli Spin Blockade
• Spin relaxation dynamics of radical-pair processes at low magnetic fields
• Defying Conventional Wisdom in Spectroscopy: Power Narrowing on IBM Quantum
• Three-photon electron spin resonances
• Non-Bloch-Siegert-type power-induced shift of two-photon electron paramagnetic resonances of charge-carrier spin states in an OLED