Nonlinear Photocurrent Dynamics

Updated 19 November 2025

Nonlinear photocurrent dynamics are defined by excitation-dependent current responses arising from higher-order light-matter interactions such as shift, injection, and chiral effects.
Experimental techniques like 2D electronic spectroscopy, excitation–correlation spectroscopy, and THz emission measurements enable precise mapping of these ultrafast, complex responses.
Understanding these dynamics drives advances in polaritonic devices, ultrafast optoelectronics, and quantum-material technologies through tailored symmetry and field-control mechanisms.

Nonlinear photocurrent dynamics describe the excitation-dependent, often non-intuitive behaviors by which photoinduced currents respond to intense, structured, or pulsed optical fields in condensed matter and optoelectronic systems. These phenomena fundamentally stem from higher-order (nonlinear) interactions between light, excitons, free carriers, polaritons, or collective modes and are governed by both symmetry and dynamical population effects. The paper of nonlinear photocurrent responses underpins advances in polaritonic devices, two-dimensional quantum materials, bulk and surface photogalvanics, terahertz and ultrafast optoelectronics, and emergent quantum phases.

1. Symmetry and Fundamental Mechanisms

Nonlinear photocurrent responses are governed by selection rules determined by crystalline and electronic symmetries, with inversion and time-reversal symmetry playing crucial roles. The prominent contributions include shift current, injection current, magnetic injection and shift currents, chiral photocurrents, photon-drag effects, and higher-order population pathways.

Shift current arises in noncentrosymmetric systems under linearly polarized light and is connected to the real-space shift of charge centers upon interband absorption. It is governed by the shift vector, a Berry connection derivative, and appears instantaneously as a dc response upon illumination (Dutta et al., 16 Jun 2025, Fei et al., 2023, Bajpai et al., 2018).
Injection current emerges primarily under circularly polarized excitation, resulting from asymmetry in group-velocity injection for carriers in different bands. It builds up on a timescale set by carrier momentum relaxation, typically becoming prominent when time-reversal or inversion symmetry is broken (Dutta et al., 16 Jun 2025, Li et al., 2020).
Magnetic injection/shift currents (MIC/MSC) appear in PT-symmetric, but individually inversion- and time-reversal-broken, systems. They are driven respectively by linearly and circularly polarized light, and originate from antisymmetric velocity differences or interband Berry curvature (Wang et al., 2020).
Chiral photocurrents are realized in parity-violating Weyl semimetals where only one (Pauli-unblocked) Weyl node dominates the nonlinear response. The in-plane orientation and amplitude are coupled to magnetization and can reach mA/W scales near resonance, with feedback on the magnetic texture through spin-transfer torque (Heidari et al., 2022).
Photon-drag effect (PDE) generates a current through momentum transfer from light to carriers, particularly notable in wide-bandgap systems with local symmetry breaking such as CVD diamond at grain boundaries (Xue et al., 2023).
Two-photon and quantum-pumping driven shift currents emerge under strong-field or pulsed excitation, enabling subgap or frequency-mixed nonlinear responses inaccessible to standard second-order theory (Bajpai et al., 2018).

2. Kinetic, Many-body, and Population Models

A variety of theoretical formalisms and kinetic models are employed to faithfully describe the transient and steady-state nonlinear photocurrent dynamics:

Coupled-rate equations: GaN-based polariton diodes, for example, require a set of coupled equations for free carriers (optically/electrically pumped), excitonic reservoirs, and bosonic polariton condensates. Above a polariton threshold, a stimulated Auger-like exciton dissociation channel produces nonlinear photocurrent enhancement proportional to the condensate occupation (Bhattacharya et al., 2018).
Quantum kinetic theory: Second-order density-matrix expansions, often in the length gauge, are used to compute the shift, injection, Berry-curvature-dipole (“nonlinear Hall”), and higher-order geometric (3-form) contributions (Li et al., 2020).
Green’s-function approaches: Many-body effects such as phonon dressing and nonreciprocity from out-of-equilibrium phonon populations are incorporated via Keldysh- or Migdal-type self-energies, modifying the selection rules and enabling BPV/BSPV even in nominally centrosymmetric crystals (Xu et al., 2022).
Quantum pumping and NEGF: For time-dependent and nonadiabatic driving, e.g., femtosecond pulses across two-terminal heterostructures, time-dependent nonequilibrium Green function methods enable full spatiotemporal mapping of nonlinear current packet propagation, revealing superballistic transport and frequency-dependent quantum pumping (Bajpai et al., 2018).
Transient population dynamics: Polaritonic photodiodes and semiconductor diodes under pulsed excitation use rate equations to monitor the time-evolution of populations, with the photocurrent following the instantaneous population difference (n_L - n_U), thereby probing interbranch scattering and detuning (Morimoto et al., 2020).

3. Experimental Methodologies for Ultrafast and Ultranonlinear Regimes

Nonlinear photocurrent dynamics are probed with a suite of techniques tailored to either ensemble-average or time-resolved regimes:

2D electronic spectroscopy (A-2DES): Phase-modulated, pulse-shaper-based setups enable the mapping of Liouville pathways contributing to the nonlinear photocurrent response up to fourth order in the electric field. Experimental constraints such as phase leakage, streaming nonlinearities, or residual population buildup require careful data-processing to extract high-fidelity 2D spectra, especially in device-relevant materials like perovskite solar cells (Amarotti et al., 3 Jun 2025).
Excitation–correlation spectroscopy (ECS): Employing phase-sensitive lock-in detection at the difference frequency of two amplitude-modulated pump arms, ECS quantitatively separates linear and nonlinear components in both time-integrated photoluminescence and photocurrent, resolving distinct pathways such as Auger, bimolecular, trap-assisted recombination, and exciton dissociation (Rojas-Gatjens et al., 2023).
THz emission and time-resolved photoconductivity: For photon-drag and plasmonic-drag effects, the transient current is monitored via the time-derivative of emitted THz fields. Mid-infrared pump–probe and electro-optic sampling of p/s-polarized field components enable separation of linear and circular PDE, quantification of emission efficiency, and extraction of carrier relaxation dynamics (Xue et al., 2023).
On-chip ultrafast electrical-probe: Sub-picosecond edge photocurrents in symmetry-engineered materials like WTe₂ are resolved using integrated ultrafast circuits, revealing bandwidths approaching 250 GHz and temperature-tunable, polarity-reversing waveforms induced by photothermoelectric effects and topology-driven transitions (Chatterjee et al., 8 Oct 2025).

4. Intensity, Frequency, and Control Parameter Dependence

Nonlinear photocurrent dynamics display diverse dependences on optical power, frequency, polarization, symmetry breaking, and external fields:

Power-law and threshold behaviors: Linear scaling at low intensity is replaced by highly nonlinear, often superlinear responses as intensity increases. In GaN polariton diodes, a 30–40% slope change occurs at a well-defined optical power coincident with the polariton lasing threshold (Bhattacharya et al., 2018). In HgTe/CdTe QWs, light-induced impact ionization produces a transition from linear to superlinear, with a characteristic threshold intensity determined by frequency and temperature (Hubmann et al., 2018).
Polarization and field control: The selection between shift, injection, and chiral currents is governed by linear vs. circular polarization and by the symmetry and topology of the underlying band structure. Application of electric (e.g., E_z) or magnetic fields can tune the spectral position, magnitude, and sign of shift and injection currents, as is especially prominent in magnetic topological quantum materials (e.g., MnBi₂Te₄) (Wang et al., 2020) and in multistate optoferroelectrics where CEP or chirp control enables dynamic current and polarization state reversal (Kazempour et al., 22 Feb 2025).
Frequency scaling and resonance: Nonlinear responses can be resonantly enhanced at band-edge or interband transition energies (e.g., Berry-curvature singularities, exciton resonances), or, for photon-drag and plasmonic-drag effects, when the frequency-to-wavevector ratio matches the Fermi velocity (Xue et al., 2023, Silkin et al., 2021).
Population effects and saturation: Saturation phenomena arise under strong-field conditions, producing complex intensity dependences or sign alternation, as in the Drude and interband edge-photogalvanic currents in graphene or in the strong-field co-circular photogalvanic regime (Candussio et al., 2021, Neufeld et al., 2021).

5. Topological, Quantum, and Emergent Phenomena

Nonlinear photocurrent serves as a direct, symmetry-selective probe of topological phase transitions, quantum geometric tensors, and emergent many-body effects:

Berry curvature and shift vector reorganization: Across Z₂ topological transitions, both shift and injection conductivities exhibit robust polarity reversals, directly reflecting band inversion and Berry curvature redistribution in time-reversal-invariant planes (Dutta et al., 16 Jun 2025). These signatures are quantitatively demonstrated in Bi₂Te₃, ZrTe₅, and BiTeI.
Quantum geometry–driven responses: Berry curvature dipole and higher 3-form geometric tensors generate nonlinear Hall and “twist” currents under circular excitation, acting as spectral and symmetry fingerprints for topological bands (Li et al., 2020).
Dynamical coupling and feedback: In parity-violating Weyl semimetals, the nonlinear chiral photocurrent dynamically rotates the magnetization through spin-transfer torque, affecting subsequent nonlinear response channels and enabling optomagnetic control (Heidari et al., 2022).
Plasmonic and photon-drag effects: Nonlocal, momentum-selective nonlinearities emerge in spatially structured or plasmonic fields when the driving wavevector and frequency approach resonance with Fermi velocity, resulting in enhanced but ultimately bounded responsivity (Silkin et al., 2021).

6. Applications and Perspectives

Nonlinear photocurrent dynamics provide foundational mechanisms and experimental pathways for advanced optoelectronic, photonic, and quantum-material systems:

Device context: Room-temperature operation and universality of nonlinear responses are observed in lateral-injection microcavity diodes, perovskite and organic photodiodes, diamond THz emitters, and 2D quantum materials (Bhattacharya et al., 2018, Rojas-Gatjens et al., 2023, Xue et al., 2023, Chatterjee et al., 8 Oct 2025).
Dynamical control and multistate logic: Ultrafast, phase-engineered pulses enable multi-bit and polarization switching in ferroelectrics at sub-picosecond timescales, promising novel nonvolatile logic and memory device architectures (Kazempour et al., 22 Feb 2025).
Photostrictive and phase transitions: Shift currents can drive nonthermal lattice strain and even phase transitions in MoS₂ and CdS, allowing light-induced control of structural orders on ultrafast timescales (Fei et al., 2023).
Topological and magnetic state readout: Bulk nonlinear photocurrents supplement or surpass surface-sensitive diagnostics for probing underlying band topology and magnetization textures (Dutta et al., 16 Jun 2025, Wang et al., 2020, Heidari et al., 2022).

Nonlinear photocurrent dynamics thus establish a central paradigm for engineering active quantum materials, probing emergent phenomena, and developing next-generation ultrafast optoelectronic and energy-harvesting technologies.