Challenging Kubo-Greenwood Theory: Nonunitarian Dynamics Reshapes THz Conductivity and Transport in Nanosystems

Field-dependent THz transport nonlinearities in semiconductor nano structures

“…With eqn (25) we have a new equation for the frequency-dependent mobility in nanosystems including nonlinear third order interaction being present at elevated field strength. Our finding reproduces the linear extended Kubo–Greenwood equation recently discovered, 32 in the weak field limit of linear response theory ( Ω → 0)containing both resonant and antiresonant contributions. As expected, reducing the interaction strength leads to the weak-field (Lorentzian and pole like) lineshapes we observed in e.g.…”

“…dephasing and relaxation). 32 For such nanowire like structures, the familiar Drude-Smith response shape emerges for long wires, however for completely different reasons than assumed backscattering at domain boundaries. 16,30 Approaching room temperature, we are confronted with another exception: the particularly small mobility (Fig.…”

“…Setting , we findand (ii) linewidth growths due to power broadening. It is worth mentioning that the equilibration current 32,34 causing the DC mobility to vanish in nanosystems is the origin of rather complicated amplitude and especially linewidth functions, see ESI,† Section S2. This is, because the Lorentzian line is highly asymmetric when the transition frequency ω 21 is low (due to the antiresonant contribution).…”

“…These phenomena show great promise for upcoming technologies like 6G telecommunication in the THz range as they allow efficient frequency generation and conversion. Although there is in-depth understanding of linear transport in bulk and nano semiconductors based on Drude, Drude-Smith and Kubo–Greenwood based models, 26–32 understanding of nonlinear transport and charge carrier mobility remains scarce. 33–36 Recent density matrix calculations show strong THz transport nonlinearity in nanowires as well as a yet unexplored equilibration current, suppressing the low-frequency charge (or exciton) mobility.…”

“…33–36 Recent density matrix calculations show strong THz transport nonlinearity in nanowires as well as a yet unexplored equilibration current, suppressing the low-frequency charge (or exciton) mobility. 32,34,37,38 The latter can be understood in the frame of a generalized Kubo–Greenwood theory including charge carrier relaxation and dephasing.…”