A curved two dimensional electron gas with spin-orbit interactions due to the radial confinement asymmetry is considered. At certain relation between the spin-orbit coupling strength and curvature radius the tangential component of the electron spin becomes a conserved quantity for any spin-independent scattering potential that leads to a number of interesting effects such as persistent spin helix and strong anisotropy of spin relaxation times. The effect proposed can be utilized in the non-ballistic spin-field-effect transistors.
We analyze the electronic properties of a two-dimensional electron gas rolled-up into a nanotube by both numerical and analytical techniques. The nature and the energy dispersion of the electronic quantum states strongly depend upon the geometric parameters of the nanotube: the typical radius of curvature and the number of windings. The effect of the curvature results in the appearance of atomic-like bound states localized near the points of maximum curvature. For a two-dimensional sheet rolled up into an Archimedean spiral we find that the number of bound states is equal to the number of wind…
The electronic properties of heterojunction electron gases formed in GaN/AlGaN core/shell nanowires with hexagonal and triangular cross-sections are studied theoretically. We show that at nanoscale dimensions, the non-polar hexagonal system exhibits degenerate quasi-one-dimensional electron gases at the hexagon corners, which transition to a core-centered electron gas at lower doping. In contrast, polar triangular core/shell nanowires show either a non-degenerate electron gas on the polar face or a single quasi-one-dimensional electron gas at the corner opposite the polar face, depending on th…
We report high-quality two-dimensional (2D) electron and hole gases induced at the surface of graphite by the electric field effect. The 2D carriers reside within a few near-surface atomic layers and exhibit mobilities up to 15,000 and 60,000 cm2/Vs at room and liquid-helium temperatures, respectively. The mobilities imply ballistic transport at micron scale. Pronounced Shubnikov-de Haas oscillations reveal the existence of two types of carries in both 2D electron and hole gases.
Tunneling between two parallel, two-dimensional electron gases (2DEGs) in a complex oxide heterostructure containing a large, mobile electron density of ~ 3x10^14 cm^-2 is used to probe the subband structure of the 2DEGs. Temperature-dependent current-voltage measurements are performed on SrTiO3/GdTiO3/SrTiO3 junctions, where GdTiO3 serves as the tunnel barrier, and each interface contains a high-density 2DEG. Resonant tunneling features in the conductance and its derivative occur when subbands on either side of the barrier align in energy as the applied bias is changed, and are used to analyz…
Graphene is the two-dimensional (2d) building block for carbon allotropes of every other dimensionality. It can be stacked into 3d graphite, rolled into 1d nanotubes, or wrapped into 0d fullerenes. Its recent discovery in free state has finally provided the possibility to study experimentally its electronic and phonon properties. Here we show that graphene's electronic structure is uniquely captured in its Raman spectrum that clearly evolves with increasing number of layers. Raman fingerprints for single-, bi- and few-layer graphene reflect changes in the electronic structure and electron-phon…
Recent claims of an experimental demonstration of spontaneous spin polarisation in dilute electron gases \cite{young99} revived long standing theoretical discussions \cite{ceper99,bloch}. In two dimensions, the stabilisation of a ferromagnetic fluid might be hindered by the occurrence of the metal-insulator transition at low densities \cite{abra79}. To circumvent localisation in the two-dimensional electron gas (2DEG) we investigated the low populated second electron subband, where the disorder potential is mainly screened by the high density of the first subband. This letter reports on the br…
We collect and review works which treat two-dimensional electron gases in quantum wells (mostly GaAs/GaAlAs heterostructures) in the presence of quantizing magnetic fields as open systems in contact with outside reservoirs. If a reservoir is sufficiently large, it pins the Fermi level to a certain energy. As a result, in a varying external magnetic field, the thermodynamic equilibrium will force oscillations of the electron density in and out of the quantum well (QW). This leads to a number of physical phenomena in magneto-transport, interband and intraband magneto-optics, magnetization, magne…
We imaged the transport of current-induced spin coherence in a two-dimensional electron gas confined in a triple quantum well. Nonlocal Kerr rotation measurements, based on the optical resonant amplification of the electrically-induced polarization, revealed a large spatial variation of the electron g factor and the efficient generation of a current controlled spin-orbit field in a macroscopic Hall bar device. We observed coherence times in the nanoseconds range transported beyond half-millimeter distances in a direction transverse to the applied electric field. The measured long spin transpor…
The response of oxide thin films to polar discontinuities at interfaces and surfaces has generated an enormous activity due to the variety of interesting effects it gives rise to. A case in point is the discovery of the electron gas at the interface between LaAlO3 and SrTiO3, which has since been shown to be quasi-two-dimensional, switchable, magnetic and/or superconducting. Despite these findings, the origin of the two-dimensional electron gas is highly debated and several possible mechanisms remain. Here we review the main proposed mechanisms and attempt to model expected effects in a quanti…
We report a comprehensive experimental study and detailed model analysis of the terahertz dielectric response and density kinetics of excitons and unbound electron-hole pairs in GaAs quantum wells. A compact expression is given, in absolute units, for the complex-valued terahertz dielectric function of intra-excitonic transitions between the 1s and higher-energy exciton and continuum levels. It closely describes the terahertz spectra of resonantly generated excitons. Exciton ionization and formation are further explored, where the terahertz response exhibits both intra-excitonic and Drude feat…
In high-mobility two-dimensional electron gases Landau levels are already formed at very small magnetic field values. Such two-dimensional electron gases show a huge negative magnetoresistance at low temperatures and an unexpected and very strong non-linear behavior with the applied current. This non-linearity depends on carrier concentration and is explained by the subtle interplay of elastic scattering within Landau levels and in between Landau levels.
We study collective excitations of a two-dimensional electron system consisting of two kinds of charge carriers: relativistic or Dirac electrons with linear dispersion and non-relativistic electrons with parabolic dispersion. We find that the strength of the interaction between the different charge carriers, i.e., the inter-species interaction, plays a significant role in determining the number of plasmon modes as well as their dispersions in certain parameter regimes.
We investigate high-mobility two-dimensional electron gases in AlGaAs heterostructures by employing Schottky-gate-dependent measurements of the samples' electron density and mobility. Surprisingly, we find that two different sample configurations can be set in situ with mobilities diering by a factor of more than two in a wide range of densities. This observation is discussed in view of charge redistributions between the doping layers and is relevant for the design of future gateable high-mobility electron gases.
We have observed that the tunneling magnetoconductance between two-dimensional (2D) electron gases formed at nominally identical InAs-AlSb interfaces most often exhibits two sets of Shubnikov-de Haas oscillations with almost the same frequency. This result is explained quantitatively with a model of the conductance in which the 2D gases have different densities and can tunnel between Landau levels with different quantum indices. When the epitaxial growth conditions of the interfaces are optimized, the zero-bias magnetoconductance shows a single set of oscillations, thus proving that the asymme…
We present magnetotransport measurements on freely suspended two-dimensional electron gases from AlGaAs/GaAs heterostructures. The technique to realize such devices relies on a specially MBE grown GaAs/AlGaAs-heterostructure including a sacrificial layer. We fabricated simple Hall-bars as well as quantum cavities and quantum dot systems. We find well-pronounced Shubnikov-de Haas oscillations and observe commensurability resonances, allowing characterization of the electron gas in these 100 nm thin membranes.
We present a variety of methods to derive the Casimir interaction in planar systems containing two-dimensional layers. Examples where this can be of use is graphene, graphene-like layers and two-dimensional electron gases. We present results for two free standing layers and for one layer above a substrate. The results can easily be extended to systems with a larger number of layers.
We have studied magnetodrag between spatially separated two dimensional electron systems due to the virtual phonon exchange with and without taking into account the screening effects. The drag rate as a function of magnetic field, temperature, and interlayer spacing is calculated.
The diffusion of energy that is locally deposited into two-dimensional electron gases by Joule heating generates transverse voltages across devices with broken symmetry. For mesoscopic structures characterized by device dimensions comparable to the energy diffusion length, the resulting thermopower strongly depends on details of the potential profile defined by electric gates. We discuss these mesoscopic features within a diffusion thermopower model and propose schemes to measure the energy diffusion length and its dependence on gate voltage.
Separately contacted double layers of a 2d electron - 2d hole gases have been prepared in GaAs separated by thin AlGaAs barriers with thicknesses down to 15 nm. The molecular-beam-epitaxial growth was interrupted just before the barrier in order to use in situ focussed-ion-beam implantation to pattern contacts which extend underneath the barrier. The two charge gases form upon biasing the p- and n-type contacts underneath and above the barrier in forward direction and show independent transistor-like behavior.
Magnetic barriers in two-dimensional electron gases are shifted in B space by homogeneous, perpendicular magnetic fields. The magnetoresistance across the barrier shows a characteristic asymmetric dip in the regime where the polarity of the homogeneous magnetic field is opposite to that one of the magnetic barrier. The measurements are in quantitative agreement with semiclassical simulations, which reveal that the magnetoresistance originates from the interplay of snake orbits with E x B drift at the edges of the Hall bar and with elastic scattering.
A poly(styrene-block-methylmethacrylate) diblock copolymer in the hexagonal cylindrical phase has been used as a mask for preparing a periodic gate on top of a Ga[Al]As-heterostructure. A superlattice period of 43 nm could be imposed onto the two-dimensional electron gas. Transport measurements show a characteristic positive magnetoresistance around zero magnetic field which we interpret as a signature of electron motion guided by the superlattice potential.
We report magneto-transport studies of InAs/GaSb bilayer quantum wells in a regime where the interlayer tunneling between the electron and hole gases is suppressed. When the chemical potential is tuned close to the charge neutrality point, we observe anomalous quantum oscillations that are inversely periodic in magnetic field and that have an extremely high frequency despite the highly insulating regime where they are observed. The seemingly contradictory coexistence of a high sheet resistance and high frequency quantum oscillations in the charge neutrality regime cannot be understood within t…
Eigenvalues and wave functions describing free electron gases in toroidal shells are determined using a basis set expansion natural to the system geometry. Couplings between azimuthal and poloidal modes are found to be appreciable at lower values of ${m_ϕ}$, modifying single particle density distributions within the shells. Thermodynamic state functions are calculated and contrasted with those of a solid toroidal volume.
We report on the observation of collective radiative decay, or superradiance, of cyclotron resonance (CR) in high-mobility two-dimensional electron gases in GaAs quantum wells using time-domain terahertz magnetospectroscopy. The decay rate of coherent CR oscillations increases linearly with the electron density in a wide range, which is a hallmark of superradiant damping. Our fully quantum mechanical theory provides a universal formula for the decay rate, which reproduces our experimental data without any adjustable parameter. These results firmly establish the many-body nature of CR decoheren…
We have performed self-consistent calculations of the nonlinear screening of a point charge Z in a two-dimensional electron gas using a density functional theory method. We find that the screened potential for a Z=1 charge supports a bound state even in the high density limit where one might expect perturbation theory to apply. To explain this behaviour, we prove a theorem to show that the results of linear response theory are in fact correct even though bound states exist.
The frictional drag force between separated but coupled two-dimensional electron gases of different temperatures is studied using the non-equilibrium Green function method based on the separation of center-of-mass and relative dynamics of electrons. As the mechanisms of producing the frictional force we include the direct Coulomb interaction, the interaction mediated via virtual and real TA and LA phonons, optic phonons, plasmons, and TA and LA phonon-electron collective modes. We found that, when the distance between the two electron gases is large, and at intermediate temperature where plasm…
We study the spin-charge conversion mechanisms in a two-dimensional gas of electrons moving in a smooth disorder potential by accounting for both Rashba-type and Mott's skew scattering contributions. We find that quantum interference effects between spin-flip and skew scattering give rise to anisotropic spin precession scattering (ASP), a direct spin-charge conversion mechanism that was discovered in an earlier study of graphene decorated with adatoms [C. Huang \emph{et al.} Phys.~Rev.~B \textbf{94} 085414.~(2016)]. Our findings suggest that, together with other spin-charge conversion mechanis…
We have fabricated high-mobility, two-dimensional electron gases in a GaAs quantum well on cylindrical surfaces, which allows to investigate the magnetotransport behavior under varying magnetic fields along the current path. A strong asymmetry in the quantum Hall effect appears for measurements on both sides of the conductive path. We determined the strain at the position of the quantum well. We observe ballistic transport in 8-micrometers-wide collimating structures.
First-principles calculations show the formation of a 2D spin polarized electron (hole) gas on the Li (CoO$_2$) terminated surfaces of finite slabs down to a monolayer of LiCoO$_2$ in remarkable contrast with the bulk band structure stabilized by Li donating its electron to the CoO$_2$ layer forming a Co-$d-t_{2g}^6$ insulator. By mapping the first-principles computational results to a minimal tight-binding models corresponding to a non-chiral 3D generalization of the quadripartite Su-Schriefer-Heeger (SSH4) model, we show that these surface states have topological origin.
Elementary electronic excitations, which are due to the Coulomb-field scatterings, present the diverse phenomena in 3D, 2D, 1D-nanotube electron gases, graphene and carbon nanotubes. The critical mechanisms cover the dimension-dependent bare Coulomb potentials, energy dispersions, and free/valence carrier density. They are responsible for the main features, the available excitation channels (the electron-hole regions), the joint van Hove singularities, the undamped/damped collective excitations at small/sufficiently high transferred momenta, the momentum dependences of plasmon frequencies (aco…
We report controlled formation of sub-100 nm-thin electron channels in SrTiO$_3$ by doping with oxygen vacancies induced by Ar$^+$-ion irradiation. The conducting channels exhibit a consistent high electron mobility (~15,000 cm$^2$V$^{-1}$s$^{-1}$), which enables clear observation of magnetic quantum oscillations, and gate-tunable linear magnetoresistance. Near the onset of electrical conduction, the metal-insulator transition is induced by the mobility suppression. With the high electron mobility and the ease of controlled channel formation, this ion-irradiation doping method may provide an e…
Shubnikov-de Haas oscillations of two-dimensional electron gases in AlYN/GaN and AlScN/GaN heterostructures
Cornell University（康奈尔大学）；Fraunhofer Institute for Applied Solid State Physics IAF（弗劳恩霍夫应用固态物理研究所）；Kavli Institute at Cornell for Nanoscale Science（康奈尔纳米科学卡弗里研究所）
In order to model the phase-coherent scattering of electrons in two-dimensional electron gases in the presence of Rashba spin-orbit coupling, a general partial-wave expansion is developed for scattering from a cylindrically symmetric potential. The theory is applied to possible electron flow imaging experiments using a moveable scanning probe microscope tip. In such experiments, it is demonstrated theoretically that the Rashba spin-orbit coupling can give rise to spin interference effects, even for unpolarized electrons at nonzero temperature and no magnetic field.
We present a systematical experimental investigation of an unusual transport phenomenon observed in two dimensional electron gases in Si/SiGe heterostructures under integer quantum Hall effect (IQHE) conditions. This phenomenon emerges under specific experimental conditions and in different material systems. It is commonly referred to as Hall resistance overshoot, however, lacks a consistent explanation so far. Based on our experimental findings we are able to develop a model that accounts for all of our observations in the framework of a screening theory for the IQHE. Within this model the or…
We present a new pseudospectral approach for incorporating many-body, nonlocal exact exchange interactions to understand the formation of electron gases in core-shell nanowires. Our approach is efficiently implemented in the open-source software package PAMELA (Pseudospectral Analysis Method with Exchange & Local Approximations) that can calculate electronic energies, densities, wavefunctions, and band-bending diagrams within a self-consistent Schrodinger-Poisson formalism. The implementation of both local and nonlocal electronic effects using pseudospectral methods is key to PAMELA's efficien…
We report on a systematic investigation of the dominant scattering mechanism in shallow two-dimensional electron gases (2DEGs) formed in modulation-doped GaAs/Al_{x}Ga_{1-x}As heterostructures. The power-law exponent of the electron mobility versus density, mu \propto n^{alpha}, is extracted as a function of the 2DEG's depth. When shallower than 130 nm from the surface, the power-law exponent of the 2DEG, as well as the mobility, drops from alpha \simeq 1.65 (130 nm deep) to alpha \simeq 1.3 (60 nm deep). Our results for shallow 2DEGs are consistent with theoretical expectations for scattering…
Inhomogeneous superconductivity in (001), (110), and (111) KTaO$_3$ two-dimensional electronic gases: effect of electronic confinement on the transition temperature
Physics Department “E.R. Caianiello”, Università degli Studi di Salerno（萨莱诺大学 E.R. Caianiello 物理系）；INFN - Sezione collegata di Salerno（意大利国家核物理研究所萨莱诺分部）；CNR-SPIN（国家研究委员会自旋科学研究所）；Physics Department “Ettore Pancini”, Università degli Studi di Napoli Federico II（那不勒斯费德里科二世大学 Ettore Pancini 物理系）
Motivated by high-accuracy scanning tunneling spectroscopy measurements on disordered two-dimensional electron gases in strong magnetic field, we present an exact solution for the local density of states (LDoS) of electrons moving in an arbitrary potential smooth on the scale of the magnetic length, that can be locally described up to its second derivatives. We use a technique based on coherent state Green's functions, allowing us to treat on an equal footing confining and open quantum systems. The energy-dependence of the LDoS is found to be universal in terms of local geometric properties, s…
We have observed long-lived (~30 ps) coherent oscillations of charge carriers due to cyclotron resonance (CR) in high-mobility two-dimensional electrons in GaAs in perpendicular magnetic fields using time-domain terahertz spectroscopy. The observed coherent oscillations were fitted well by sinusoids with exponentially-decaying amplitudes, through which we were able to provide direct and precise measures for the decay times and oscillation frequencies simultaneously. This method thus overcomes the CR saturation effect, which is known to prevent determination of true CR linewidths in high-mobili…
We study entanglement of electron spins in many-body systems based on the Green's function approach. As an application we obtain the two-particle density matrix of a non-interacting electron gas and identify its two-spin density matrix as a Werner state. We calculate entanglement measures, a classical correlation, mutual information, and a pair distribution function of two electrons at zero and finite temperatures. We find that changes of entanglement measures are proportional to $T^2$ at low temperatures.
In a two dimensional electron gas with Rashba spin-orbit coupling, the external electric field may cause a spin Hall current in the direction perpendicular to the electric field. This effect was called the intrinsic spin Hall effect. In this paper, we investigate the influences of spin accumulation on this intrinsic spin Hall effect. We show that due to the existence of boundaries in a real sample, the spin Hall current generated by the intrinsic spin Hall effect will cause spin accumulation near the edges of the sample, and in the presence of spin accumulation, the spin Hall conductivity will…
We present theoretical calculations for the spectral functions and single-particle densities of states of the two-dimensional electron gas in semiconductor quantum wells at different electron densities using the GW+cumulant method. We compare our results to GW only calculations and find significant differences in the description of the satellites between the two theories: while GW theory predicts the existence of a plasmaron excitation, no such excitation is found in GW+cumulant theory. We compare our results to experimental tunneling spectra from semiconductor quantum wells and find good agre…
We study the effect of disorder on the intrinsic anomalous Hall (AH) conductivity in a spin-polarized two-dimensional electron gas with a Rashba-type spin-orbit interaction. We find that AH conductivity vanishes unless the lifetime is spin-dependent, similar to the spin Hall (SH) conductivity in the non-magnetic system. In addition, we find that the SH conductivity does not vanish in the presence of magnetic scatterers. We show that the SH conductivity can be controlled by changing the amount of the magnetic impurities.
We review some of our recent experimental studies on low-carrier concentration, mesoscopic two-dimensional electron gases (m2DEGs). The m2DEGs show a range of striking characteristics including a complete avoidance of the strongly localised regime even when the electrical resistivity $ρ>> h/e^2$, giant thermoelectric response, and an apparent decoupling of charge and thermoelectric transport. We analyse the results and demonstrate that these observations can be explained based on the assumption that the charge carriers retain phase coherence over the m2DEG dimensions. Intriguingly, this would …
Analysis of the electronic structure of an ordinary two-dimensional electron gas (2DEG) under an appropriate external periodic potential of hexagonal symmetry reveals that massless Dirac fermions are generated near the corners of the supercell Brillouin zone. The required potential parameters are found to be achievable under or close to laboratory conditions. Moreover, the group velocity is tunable by changing either the effective mass of the 2DEG or the lattice parameter of the external potential, and it is insensitive to the potential amplitude. The finding should provide a new class of syst…
We investigate the conductance properties of a hybrid ferromagnet-semiconductor structure consisting of a confined two-dimensional electron gas and a transverse ferromagnetic strip on top. Within the framework of the Landauer-Büttiker model, we develop an alternative way to consider magnetic fields. Our method describes devices ranging from a recently realized nanomagnetometer down to quasi one-dimensional quantum wires. We provide a rigorous way to relate the measured resistance to the actual magnetization of the strip. Regarding the quasi one-dimensional wires we propose a new device applica…
GaAs-based two-dimensional electron gases (2DEGs) show a wealth of remarkable electronic states, and serve as the basis for fast transistors, research on electrons in nanostructures, and prototypes of quantum-computing schemes. All these uses depend on the extremely low levels of disorder in GaAs 2DEGs, with low-temperature mean free paths ranging from microns to hundreds of microns. Here we study how disorder affects the spatial structure of electron transport by imaging electron flow in three different GaAs/AlGaAs 2DEGs, whose mobilities range over an order of magnitude. As expected, electro…
We have experimentally studied the spin-induced time reversal symmetry (TRS) breaking as a function of the relative strength of the Zeeman energy (E_Z) and the Rashba spin-orbit interaction energy (E_SOI), in InGaAs-based 2D electron gases. We find that the TRS breaking saturates when E_Z becomes comparable to E_SOI. Moreover, we show that the spin-induced TRS breaking mechanism is a universal function of the ratio E_Z/E_SOI, within the experimental accuracy.
We present thermopower $S$ and resistance $R$ measurements on GaAs-based mesoscopic two-dimensional electron gases (2DEGs) as functions of the electron density $n_s$. At high $n_s$ we observe good agreement between the measured $S$ and $S_{\rm{MOTT}}$, the Mott prediction for a non-interacting metal. As $n_s$ is lowered, we observe a crossover from Mott-like behaviour to that where $S$ shows strong oscillations and even sign changes. Remarkably, there are absolutely no features in $R$ corresponding to those in $S$. In fact, $R$ is devoid of even any universal conductance fluctuations. A statis…
The branched pattern typically observed through the scanning gate microscopy (SGM) of two dimensional electron gases in the presence of weak, smooth disorder has recently been found to be robust against a very large shift in the Fermi energy of the electron gas. We propose a toy model, where the potential landscape reduces to a single localized feature, that makes it possible to recast the understanding of branch formation through the effect of caustics in an appropriate set of classical trajectories, and it is simple enough to allow for a quantitative analysis of the energy and spatial depend…
The role of optical-phonons in frictional drag between two adjacent but electrically isolated two-dimensional electron gases is investigated. Since the optical-phonons in III-V materials have a considerably larger coupling to electrons than acoustic phonons (which are the dominant drag mechanism at low T and large separations) it might be expected that the optical phonons will give a large effect high temperatures. The two key differences between optical and acoustic phonon mediated drag are: (1) the optical phonon mediated interlayer interaction is short-ranged due to their negligible group v…
We study the spin polarization induced by a current flow in clean two dimensional electron gases with Rashba spin-orbit coupling. This geometric effect originates from special properties of the electron's scattering at the edges of the sample. In wide samples, the spin polarization has it largest value at low energies (close to the bottom of the band) and goes to zero at higher energies. In this case, the spin polarization is dominated by the presence of evanescent modes which have an explicit spin component outside the plane. In quantum wires, on the other hand, the spin polarization is domin…
We present longitudinal and Hall magneto-resistance measurements of a ``magnetic'' two-dimensional electron gas (2DEG) formed in modulation-doped Zn$_{1-x-y}$Cd$_{x}$Mn$_{y}$Se quantum wells. The electron spin splitting is temperature and magnetic field dependent, resulting in striking features as Landau levels of opposite spin cross near the Fermi level. Magnetization measurements on the same sample probe the total density of states and Fermi energy, allowing us to fit the transport data using a model involving extended states centered at each Landau level and two-channel conduction for spin-…
We show that current in a two-dimensional electron gas (2DEG) can trap ultracold atoms $<1 μ$m away with orders of magnitude less spatial noise than a metal trapping wire. This enables the creation of hybrid systems, which integrate ultracold atoms with quantum electronic devices to give extreme sensitivity and control: for example, activating a single quantized conductance channel in the 2DEG can split a Bose-Einstein condensate (BEC) for atom interferometry. In turn, the BEC offers unique structural and functional imaging of quantum devices and transport in heterostructures and graphene.
We present measurements of the energy relaxation length scale $\ell$ in two-dimensional electron gases (2DEGs). A temperature gradient is established in the 2DEG by means of a heating current, and then the elevated electron temperature $T_e$ is estimated by measuring the resultant thermovoltage signal across a pair of deferentially biased bar-gates. We adapt a model by Rojek and König [Phys. Rev. B \textbf{90}, 115403 (2014)] to analyse the thermovoltage signal and as a result extract $\ell$, $T_e$, and the power-law exponent $α_i$ for inelastic scattering events in the 2DEG. We show that in h…
We demonstrate tunable transverse rectification in a density-modulated two-dimensional electron gas (2DEG). The density modulation is induced by two surface gates, running in parallel along a narrow stripe of 2DEG. A transverse voltage in the direction of the density modulation is observed, i.e. perpendicular to the applied source-drain voltage. The polarity of the transverse voltage is independent of the polarity of the source-drain voltage, demonstrating rectification in the device. We find that the transverse voltage $U_{y}$ depends quadratically on the applied source-drain voltage and non-…
We calculate the linear conductance of a two-dimensional electron gas (2DEG)-based junction between a normal semiconductor section and a hybrid semiconductor-superconductor section, under perpendicular magnetic field. We consider two important terms often neglected in the literature, the magneto-orbital and transverse Rashba spin-orbit. The strong orbital effect due to the magnetic field yields topological phase transitions to nontrivial phases hosting Majorana modes in the hybrid section. The presence of a potential barrier at the junction interface reveals the Majorana phases as quantized pl…
