Electronic properties of semiconductor quantum wires for shallow symmetric and asymmetric confinements

2021 ◽  
Author(s):  
Irina I. Yakimenko ◽  
Ivan P. Yakimenko
Keyword(s):  
Electron Transport ◽  
Density Functional ◽  
Quantum Wires ◽  
Zero Magnetic Field ◽  
Electron Interaction ◽  
Spin Polarized ◽  
Quantum Point ◽  
Dimensional Electron Gas ◽  
The One ◽  
Quantum Technology

Abstract Quantum wires (QWs) and quantum point contacts (QPCs) have been realized in GaAs/AlGaAs heterostructures in which a two-dimensional electron gas (2DEG) resides at the interface between GaAs and AlGaAs layered semiconductors. The electron transport in these structures has previously been studied experimentally and theoretically, and a 0.7 conductance anomaly has been discovered. The present paper is motivated by experiments with a QW in shallow symmetric and asymmetric confinements that have shown additional conductance anomalies at zero magnetic field. The proposed device consists of a QPC that is formed by split gates and a top gate between two large electron reservoirs. This paper is focused on the theoretical study of electron transport through a wide top-gated QPC in a low-density regime and is based on density functional theory. The electron-electron interaction and shallow confinement make the splitting of the conduction channel into two channels possible. Each of them becomes spin-polarized at certain split and top gates voltages and may contribute to conductance giving rise to additional conductance anomalies. For symmetrically loaded split gates two conduction channels contribute equally to conductance. For the case of asymmetrically applied voltage between split gates conductance anomalies may occur between values of 0.25(2e2/h) and 0.7(2e2/h) depending on the increased asymmetry in split gates voltages. This corresponds to different degrees of spin-polarization in the two conduction channels that contribute differently to conductance. In the case of a strong asymmetry in split gates voltages one channel of conduction is pinched off and just the one remaining channel contributes to conductance. We have found that on the perimeter of the anti-dot there are spin-polarized states. These states may also contribute to conductance if the radius of the anti-dot is small enough and tunnelling between these states may occur. The spin-polarized states in the QPC with shallow confinement tuned by electric means may be used for the purposes of quantum technology.

scholarly journals Quantum conductance staircase of holes in silicon nanosandwiches

2019 ◽  
Vol 20 (2) ◽  
pp. 81-98
Author(s):  
N. T. Bagraev ◽  
L. E. Klyachkin ◽  
A. M. Malyarenko ◽  
V. S. Khromov
Keyword(s):  
Kinetic Energy ◽  
Quantum Wells ◽  
Quantum Wires ◽  
Energy Gap ◽  
Point Contact ◽  
Quantum Conductance ◽  
One Dimensional ◽  
Drastic Increase ◽  
Quantum Point ◽  
The One

The results of studying the quantum conductance staircase of holes in one−dimensional channels obtained by the split−gate method inside silicon nanosandwiches that are the ultra−narrow quantum well confined by the delta barriers heavily doped with boron on the n−type Si (100) surface are reported. Since the silicon quantum wells studied are ultra−narrow (~2 nm) and confined by the delta barriers that consist of the negative−U dipole boron centers, the quantized conductance of one−dimensional channels is observed at relatively high temperatures (T > 77 K). Further, the current−voltage characteristic of the quantum conductance staircase is studied in relation to the kinetic energy of holes and their sheet density in the quantum wells. The results show that the quantum conductance staircase of holes in p−Si quantum wires is caused by independent contributions of the one−dimensional (1D) subbands of the heavy and light holes; these contributions manifest themselves in the study of square−section quantum wires in the doubling of the quantum−step height (G0 = 4e2/h), except for the first step (G0 = 2e2/h) due to the absence of degeneracy of the lower 1D subband. An analysis of the heights of the first and second quantum steps indicates that there is a spontaneous spin polarization of the heavy and light holes, which emphasizes the very important role of exchange interaction in the processes of 1D transport of individual charge carriers. In addition, the field−related inhibition of the quantum conductance staircase is demonstrated in the situation when the energy of the field−induced heating of the carriers become comparable to the energy gap between the 1D subbands. The use of the split−gate method made it possible to detect the effect of a drastic increase in the height of the quantum conductance steps when the kinetic energy of holes is increased; this effect is most profound for quantum wires of finite length, which are not described under conditions of a quantum point contact. In the concluding section of this paper we present the findings for the quantum conductance staircase of holes that is caused by the edge channels in the silicon nanosandwiches prepared within frameworks of the Hall. This longitudinal quantum conductance staircase, Gxx, is revealed by the voltage applied to the Hall contacts, Vxy, to a maximum of 4e2/h. In addition to the standard plateau, 2e2/h, the variations of the Vxy voltage appear to exhibit the fractional forms of the quantum conductance staircase with the plateaus and steps that bring into correlation respectively with the odd and even fractional values.

Strain modulation on spin transport properties of PTB junction with MoC2 electrodes

2021 ◽  
Author(s):  
Yaoxing Sun ◽  
Bei Zhang ◽  
shidong zhang ◽  
Dan Zhang ◽  
Jiwei Dong ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Electron Transport ◽  
Transport Properties ◽  
Density Functional ◽  
Spin Transport ◽  
Functional Theory ◽  
Spintronic Devices ◽  
Spin Polarized ◽  
Electron Transport Properties ◽  
Strain Modulation

Based on MoC2 nanoribbons and poly-(terphenylene-butadiynylene) (PTB) molecules, we designed MoC2-PTB molecular spintronic devices and investigated their spin-dependent electron transport properties by using spin-polarized density functional theory and non-equilibrium Green's...

Large optical singularities of the one-dimensional electron gas in semiconductor quantum wires

1991 ◽  
Vol 79 (11) ◽  
pp. 911-915 ◽  
Author(s):  
J.M. Calleja ◽  
A.R. Goñi ◽  
B.S. Dennis ◽  
J.S. Weiner ◽  
A. Pinczuk ◽  
...  
Keyword(s):  
Quantum Wires ◽  
Electron Gas ◽  
Dimensional Electron ◽  
One Dimensional ◽  
Dimensional Electron Gas ◽  
The One

VOLTAGE-TUNABLE SPIN POLARIZATION OF TWO-DIMENSIONAL ELECTRON GAS IN FERROMAGNETIC/SEMICONDUCTOR HYBRID NANOSYSTEM

2006 ◽  
Vol 13 (05) ◽  
pp. 599-605
Author(s):  
MAOWANG LU
Keyword(s):  
Electron Transport ◽  
Applied Voltage ◽  
Electron Gas ◽  
Two Dimensional ◽  
Dimensional Electron ◽  
Two Dimensional Electron Gas ◽  
Alternative Scheme ◽  
Spin Polarized ◽  
Dimensional Electron Gas ◽  
Hybrid Nanosystem

The spin-dependent electron transport in a two-dimensional electron gas (2DEG) modulated by a stripe of magnetized ferromagnetic metal under an applied voltage was investigated theoretically. It is revealed that highly spin-polarized current can be achieved in this kind of nanosystems. It is also shown that the spin polarity of the electron transport can be switched by adjusting the applied voltage to the stripe in the device. These interesting properties may provide an alternative scheme to spin polarize electrons into semiconductors, and this device may be used as a voltage-tunable spin filter.

SPONTANEOUS SPIN POLARIZATION OF ELECTRONS IN SiGe/Si HETEROSTRUCTURES

2010 ◽  
Vol 09 (05) ◽  
pp. 503-509
Author(s):  
A. JOHN PETER
Keyword(s):  
Zero Magnetic Field ◽  
Spin Orbit Coupling ◽  
Spin Orbit ◽  
Resonant Level ◽  
Electron Transmission ◽  
Rashba Spin ◽  
Spin Polarized ◽  
Spin Filters ◽  
Spin Injectors ◽  
The One

The spin-dependent electron transmission phenomenon in an SiGe/Si/SiGe resonant semiconductor heterostructure is employed theoretically to investigate the output transmission current polarization at zero magnetic field. Transparency of electron transmission is calculated as a function of electron energy as well as the well width, within the one electron band approximation along with the spin-orbit interaction. Enhanced spin-polarized resonant tunneling in the heterostructure due to Dresselhaus and Rashba spin-orbit coupling induced splitting of the resonant level is observed. We predict that a spin-polarized current spontaneously emerges in this heterostructure and we estimate theoretically that the polarization can reach 100%. This effect could be employed in the fabrication of spin filters, spin injectors, and detectors based on nonmagnetic semiconductors.

Optical singularities of the one-dimensional electron gas in semiconductor quantum wires

1992 ◽  
Vol 263 (1-3) ◽  
pp. 346-350 ◽  
Author(s):  
J.M. Calleja ◽  
A.R. Goñi ◽  
B.S. Dennis ◽  
J.S. Weiner ◽  
A. Pinczuk ◽  
...  
Keyword(s):  
Quantum Wires ◽  
Electron Gas ◽  
Dimensional Electron ◽  
One Dimensional ◽  
Dimensional Electron Gas ◽  
The One

scholarly journals Defect processes in F and Cl doped anatase TiO2

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Petros-Panagis Filippatos ◽  
Nikolaos Kelaidis ◽  
Maria Vasilopoulou ◽  
Dimitris Davazoglou ◽  
Nektarios N. Lathiotakis ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Photocatalytic Activity ◽  
Electron Transport ◽  
Transition Metal Oxides ◽  
Density Functional ◽  
Defect Engineering ◽  
Functional Theory ◽  
Spin Polarized ◽  
Engineering Strategy ◽  
Complete Investigation

AbstractTitanium dioxide represents one of the most widely studied transition metal oxides due to its high chemical stability, non-toxicity, abundance, electron transport capability in many classes of optoelectronic devices and excellent photocatalytic properties. Nevertheless, the wide bang gap of pristine oxide reduces its electron transport ability and photocatalytic activity. Doping with halides and other elements has been proven an efficient defect engineering strategy in order to reduce the band gap and maximize the photocatalytic activity. In the present study, we apply Density Functional Theory to investigate the influence of fluorine and chlorine doping on the electronic properties of TiO2. Furthermore, we present a complete investigation of spin polarized density functional theory of the (001) surface doped with F and Cl in order to elaborate changes in the electronic structure and compare them with the bulk TiO2.

Sign in / Sign up

Export Citation Format

Share Document