Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userElectrostatic confinement of electrons in an integrable graphene quantum dot
136
0
0.0
(
0
)
Added by
Jens Hjorleifur Bardarson
Publication date
2009
fields
Physics
and research's language is
English
Ask ChatGPT about the research
No Arabic abstract
We compare the conductance of an undoped graphene sheet with a small region subject to an electrostatic gate potential for the cases that the dynamics in the gated region is regular (disc-shaped region) and classically chaotic (stadium). For the disc, we find sharp resonances that narrow upon reducing the area fraction of the gated region. We relate this observation to the existence of confined electronic states. For the stadium, the conductance looses its dependence on the gate voltage upon reducing the area fraction of the gated region, which signals the lack of confinement of Dirac quasiparticles in a gated region with chaotic classical electron dynamics.
rate research
Read More
We investigate the electrostatic confinement of charge carriers in a gapped graphene quantum dot in the presence of a magnetic flux. The circular quantum dot is defined by an electrostatic gate potential delimited in an infinite graphene sheet which is then connected to a two terminal setup. Considering different regions composing our system, we explicitly determine the solutions of the energy spectrum in terms of Hankel functions. Using the scattering matrix together with the asymptotic behavior of the Hankel functions for large arguments, we calculate the density of states and show that it has an oscillatory behavior with the appearance of resonant peaks. It is found that the energy gap can controls the amplitude and width of these resonances and affect their location in the density of states profile.
Using real-time charge sensing and gate pulsing techniques we measure the ratio of the rates for tunneling into the excited and ground spin states of a single-electron AlGaAs/GaAs quantum dot in a parallel magnetic field. We find that the ratio decreases with increasing magnetic field until tunneling into the excited spin state is completely suppressed. However, we find that by adjusting the voltages on the surface gates to change the orbital configuration of the dot we can restore tunneling into the excited spin state and that the ratio reaches a maximum when the dot is symmetric.
We present a proposal for deterministic quantum teleportation of electrons in a semiconductor nanostructure consisting of a single and a double quantum dot. The central issue addressed in this paper is how to design and implement the most efficient - in terms of the required number of single and two-qubit operations - deterministic teleportation protocol for this system. Using a group-theoretical analysis we show that deterministic teleportation requires a minimum of three single-qubit rotations and two entangling (sqrt(swap)) operations. These can be implemented for spin qubits in quantum dots using electron spin resonance (for single-spin rotations) and exchange interaction (for sqrt(swap) operations).
Correlation among particles in finite quantum systems leads to complex behaviour and novel states of matter. One remarkable example is predicted to occur in a semiconductor quantum dot (QD) where at vanishing density the Coulomb correlation among electrons rigidly fixes their relative position as that of the nuclei in a molecule. In this limit, the neutral few-body excitations are roto-vibrations, which have either rigid-rotor or relative-motion character. In the weak-correlation regime, on the contrary, the Coriolis force mixes rotational and vibrational motions. Here we report evidence of roto-vibrational modes of an electron molecular state at densities for which electron localization is not yet fully achieved. We probe these collective modes by inelastic light scattering in QDs containing four electrons. Spectra of low-lying excitations associated to changes of the relative-motion wave function -the analogues of the vibration modes of a conventional molecule- do not depend on the rotational state represented by the total angular momentum. Theoretical simulations via the configuration-interaction (CI) method are in agreement with the observed roto-vibrational modes and indicate that such molecular excitations develop at the onset of short-range correlation.
We consider a square lattice configuration of circular gate-defined quantum dots in an unbiased graphene sheet and calculate the electronic, particularly spectral properties of finite albeit actual sample sized systems by means of a numerically exact kernel polynomial expansion technique. Analyzing the local density of states and the momentum resolved photoemission spectrum we find clear evidence for a series of quasi-bound states at the dots, which can be probed by optical measurements. We further analyze the interplay of the superlattice structure with dot localized modes on the electron energy dispersion. Effects of disordered dot lattices are discussed too.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
