Decoding the conductance of disordered nanostructures: a quantum inverse problem

Obtaining conductance spectra for a concentration of disordered impurities distributed over a nanoscale device with sensing capabilities is a well-defined problem. However, to do this inversely, i.e., extracting information about the scatters from the conductance spectrum alone, is not an easy task. In the presence of impurities, even advanced techniques of inversion can become particularly challenging. This article extends the applicability of a methodology we proposed capable of extracting composition information about a nanoscale sensing device using the conductance spectrum. The inversion tool decodes the conductance spectrum to yield the concentration and nature of the disorders responsible for conductance fluctuations in the spectra. We present the method for simple one-dimensional systems like an electron gas with randomly distributed delta functions and a linear chain of atoms. We prove the generality and robustness of the method using materials with complex electronic structures like hexagonal boron nitride, graphene nanoribbons, and carbon nanotubes. We also go on to probe distribution of disorders on the sublattice structure of the materials using the proposed inversion tool.

Spin filtering and magnetically-controlled quantum switch in multiple triangular rings consisting of quantum dots

Electron transport characteristics through a system consisting of a series of triangular quantum dot rings are studied utilizing the non-equilibrium Green’s function. In the presence of a magnetic field, an additional anti-resonance point occurs in the conductance spectrum. As the number of triangular quantum dot rings increases, two anti-resonance points evolve into two well-defined insulating bands. The insulating band disappears as the magnetic flux takes an appropriate value, and therefore, an effective magnetically-controlled quantum switch can be achieved. If a Zeeman magnetic field is introduced, a spin-polarized window (SPW) can be formed, suggesting a physical scheme of a spin filtering. As the intradot Coulomb interactions are taken into consideration, more SPWs can be obtained. This work sheds lights onto the design of future quantum devices.

Andreev conductance through a triangular-shaped quantum dot structure hosting Majorana bound states

The Andreev conductance in [Formula: see text]-shaped quantum dots (QDs) system coupled with Majorana bound states (MBSs) is studied and resulting conductance spectrum displays resonant and non-resonant processes. These fluctuated resonances render features like insulating band, bonding (antibonding) in the low-bias region due to non-trivial role of interdot coupling [Formula: see text] and dots-MBSs coupling [Formula: see text]. On comparing QD levels [Formula: see text], and the coupling between the MBSs, coherent oscillating dynamics of an electron between the nanowire and the QDs can be portrayed. The insulating band is robust against [Formula: see text], but highly sensitive to [Formula: see text], which causes to increase (decrease) the conductance. We can claim that under finite bias voltage, transport can facilitate the researchers to expose the essential features of the Majorana fermion in such closed systems composed of MBSs.

Damage Monitoring Research of the Concrete Structure Based on the Piezoelectric Impedance

Based on the piezoelectric impedance technology, damages in concrete specimens could be monitored. The structural damages were simulated by pasting piezoelectric ceramic chips and boring several holes on the surface of concrete specimens. And then, with the precision impedance analyzer HP4192A, we measured the conductance spectrum curve of the specimens.The specimens were in two different damage situations：one was damaged in one place to varying degrees and the other was damaged in different locations to the same degree. The experiment results show that the damages in the specimens can lead to the drift of the conductance spectrum curve and the greater the damages are, the greater the change will be.

The Electronic Transports Technology in a T-Shaped Double Quantum Dot

We study the phonon-assisted Fano interference of the linear conductance spectrum by taking into account the interdot-phonon exchange in a T-shaped double quantum dot (QD), where a central QD is coupled to a side QD and two nonmagnetic or ferromagnetic electrodes. Unlike the usual Fano interference between different elastic channels,this new-type Fano interference is shown to arise from electron waves tunneling coherently through phonon-assisted bonding and antibonding states.

COULOMB BLOCKADE IN GRAPHENE QUANTUM DOTS

We study the conductance spectrum of graphene quantum dots, both single- and multiple-dot cases. The single electron tunneling through a graphene dot is investigated and the periodicity, amplitude and line shape of the Coulomb blockade oscillations at low temperatures are obtained, which are consistent with the recent experimental observations. Further, we discuss the transport behavior when multiple dots are assembled in array and find a phase transition of conductance spectra from individual Coulomb blockade to collective Coulomb blockade.