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Register a new userCarrier thermalization dynamics in single Zincblende and Wurtzite InP nanowires
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Using transient Rayleigh scattering (TRS) measurements, we obtain photoexcited carrier thermalization dynamics for both zincblende (ZB) and wurtzite (WZ) InP single nanowires (NW) with picosecond resolution. A phenomenological fitting model based on direct band to band transition theory is developed to extract the electron-hole-plasma density and temperature as a function of time from TRS measurements of single nanowires which have complex valence band structures. We find that the thermalization dynamics of hot carriers depends strongly on material (GaAs NW vs. InP NW) and less strongly on crystal structure (ZB vs. WZ). The thermalization dynamics of ZB and WZ InP NWs are similar. But a comparison of the thermalization dynamics in ZB and WZ InP NWs with ZB GaAs NW reveals more than an order of magnitude slower relaxation for the InP NWs. We interpret these results as reflecting their distinctive phonon band structures which lead to different hot phonon effects. Knowledge of hot carrier thermalization dynamics is an essential component for effective incorporation of nanowire materials into electronic devices.
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In this study, we present a complete experimental and theoretical investigation of the fundamental exciton Zeeman splitting in wurtzite InP nanowires. We determined the exciton gyromagnetic factor, $g_{exc}$, by magneto-photoluminescence spectroscopy using magnetic fields up to 29 T. We found that $g_{exc}$ is strongly anisotropic with values differing in excess of 50% between the magnetic field oriented parallel and perpendicular to the nanowire long axis. Furthermore, for magnetic fields oriented along the nanowire axis, $g_{exc}$ is nearly three times larger than in bulk zincblende InP and it shows a marked sublinear dependence on the magnetic field, a common feature to other non-nitride III-V wurtzite nanowires but not properly understood. Remarkably, this nonlinearity originates from only one Zeeman branch characterized by a specific type of light polarization. All the experimental findings are modeled theoretically by a robust approach combining the $k cdot p$ method with the envelope function approximation and including the electron-hole interaction. We revealed that the nonlinear features arise due to the coupling between Landau levels pertaining to the A (heavy-hole like) and B (light-hole like) valence bands of the wurtzite crystal structure. This general behavior is particularly relevant for the understanding of the spin properties of several wurtzite nanowires that host the set for the observation of topological phases potentially at the base of quantum computing platforms.
We have performed a detailed study of the lattice distortions of InP wurtzite nanowires containing an axial screw dislocation. Eshelby predicted that this kind of system should show a crystal rotation due to the dislocation induced torque. We have measured the twisting rate and the dislocation Burgers vector on individual wires, revealing that nanowires with a 10-nm radius have a twist up to 100% larger than estimated from elasticity theory. The strain induced by the deformation has a Mexican-hat-like geometry, which may create a tube-like potential well for carriers.
We compare the electronic characteristics of nanowire field-effect transistors made using single pure wurtzite and pure zincblende InAs nanowires with nominally identical diameter. We compare the transfer characteristics and field-effect mobility versus temperature for these devices to better understand how differences in InAs phase govern the electronic properties of nanowire transistors.
We analyze the process of thermalization, dynamics and the eigenstate thermalization hypothesis (ETH) for the single impurity Anderson model, focusing on the Kondo regime. For this we construct the complete eigenbasis of the Hamiltonian using the numerical renormalization group (NRG) method in the language of the matrix product states. It is a peculiarity of the NRG that while the Wilson chain is supposed to describe a macroscopic bath, very few single particle excitations already suffice to essentially thermalize the impurity system at finite temperature, which amounts to having added a macroscopic amount of energy. Thus given an initial state of the system such as the ground state together with microscopic excitations, we calculate the spectral function of the impurity using the microcanonical and diagonal and grand canonical ensembles. By adding or removing particles at a certain Wilson energy shell on top of the ground state, we find qualitative agreement between the spectral functions calculated for different ensembles. This indicates that the system thermalizes in the long-time limit, and can be described by an appropriate statistical-mechanical ensemble. Moreover, by calculating the impurity spectral density at the Fermi level and the dot occupancy for energy eigenstates relevant for microcanonical ensemble, we find good support for ETH. The ultimate mechanism responsible for this effective thermalization within the NRG can be identified as Anderson orthogonality: the more charge that needs to flow to or from infinity after applying a local excitation within the Wilson chain, the more the system looks thermal afterwards at an increased temperature. For the same reason, however, thermalization fails if charge rearrangement after the excitation remains mostly local.
The authors combine acousto-optoelectric and multi-channel photon correlation spectroscopy to probe spatio-temporal carrier dynamics induced by a piezoelectric surface acoustic wave (SAW). The technique is implemented by combining phase-locked optical micro-photoluminescence spectroscopy and simultaneous three-channel time resolved detection. From the recorded time correlated single photon counting data the time transients of individual channels and the second and third order correlation functions are obtained with sub-nanosecond resolution. The method is validated by probing the correlations SAW-driven carrier dynamics between three decay channels of a single polytypic semiconductor nanowire on a conventional LiNbO$_mathrm{3}$ SAW delay line chip. The method can be readily applied to other types of nanosystems and probe SAW-regulated charge state preparation in quantum dots, charge transfer processes in van der Waals heterostructures or other types of hybrid nanoarchitectures.
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