Ben Yu-Kuang Hu

University of Akron · Department of Physics

In a recent paper (2022 Eur . J . Phys . 43 035 004) Lineros considers a block (not necessarily initially at rest) which slides down from the top of a frictionless horizontal movable semi-sphere. The author studies the angle at which the block loses contact with the sphere and derives a cubic equation which determines that angle. In this comment, a...

An alternative elementary argument for the magnetic field outside a solenoid is described.

An alternative elementary argument for the magnetic field outside a solenoid is described.

Coulomb drag is a favored experimental probe of Coulomb interactions between layers of 2D materials. In reality, these layers display spatial charge density fluctuations known as puddles due to various imperfections. A theoretical formalism for incorporating density inhomogeneity into calculations has however not been developed, making the understa...

We develop the diagrammatic formulation of the many-body theory for the coupled collective modes in interacting electron systems of different dimensions. The formalism is then applied in detail to a two-dimensional system coupled to a three-dimensional electron gas. We find two dimensionally-mixed plasmon modes which in the long wavelength limit ar...

We develop the diagrammatic formulation of the many-body theory for the coupled collective modes in interacting electron systems of different dimensions. The formalism is then applied in detail to a two-dimensional system coupled to a three-dimensional electron gas. We find two dimensionally-mixed plasmon modes which in the long wavelength limit ar...

We develop a theory of Coulomb drag due to momentum transfer between graphene layers in a strong magnetic field. The theory is intended to apply in systems with disorder that is weak compared to Landau level separation, so that Landau level mixing is weak, but strong compared to correlation energies within a single Landau level, so that fractional...

Coulomb drag is a direct measurement of the electron-electron interactions between two electronic layers. Graphene is a versatile electronic material with a high-degree of tunability opening up regimes that were not previously accessible. All previous theoretical studies of graphene Coulomb drag away from charge neutrality assume a spatially homoge...

We study two-stream instabilities in a non-equilibrium system in which a stream of electrons is injected into doped graphene. As with equivalent non-equilibrium parabolic band systems, we find that the graphene systems can support unstable charge-density waves whose amplitudes grow with time. We determine the range of wavevector $\boldsymbol{q}$ th...

The total linear electromagnetic field momentum $\mathbf P_{\mathrm{em}}$ of a stationary electric dipole $\mathbf p$ in a static magnetic field $\mathbf B$ is considered. The expression $\mathbf P_{\mathrm{em}} = \frac12\mathbf B \times \mathbf p$, which has previously reported to hold in all static magnetic field situations, is not valid in gener...

We consider electronic collective modes in coupled systems in which the individual components have different dimensionalities. Many-body diagramnatic techniques are used to derive formal results for the screened intra- and inter-system Coulomb interaction. We specifically investigate the case of a quasi-one-dimensional quantum wire in close proximi...

I describe an elementary way of introducing electromagnetic field momentum. By considering a system of a long solenoid and line charge, the dependence of the field momentum on the electric and magnetic fields can be deduced. I obtain the electromagnetic angular momentum for a point charge and magnetic monopole pair partially through dimensional ana...

We reexamine Feynman's angular momentum paradox, in which a cylinder of charge around a current carrying solenoid is set in rotational motion when the current is turned off (due to the induced electric field caused by the change in magnetic flux), apparently violating conservation of angular momentum. The standard explanation of the resolution of t...

Electron--electron scattering in graphene does not conserve electrical current, because of the linear dispersion of the bands in graphene near the Dirac point. In graphene, when two electrons with initial momenta k1 and k2 undergo electron--electron scattering to final states k1' and k2', in general the total current v(k1) + v(k2) v(k1') + v(k2') [...

In recent papers, Turner and Turner (2010 Am. J. Phys. 78 905–7) and Jensen (2011 Eur. J. Phys. 32 389–97) analysed the motion of asymmetric rolling rigid bodies on a horizontal plane. These papers addressed the common misconception that the instantaneous point of contact of the rolling body with the plane can be used to evaluate the angular moment...

In a recent papers, Turner and Turner (2010 {\em Am. J. Phys.} {\bf 78} 905-7) and Jensen (2011 {\em Eur. J. Phys.} {\bf 32} 389-397) analysed the motion of asymmetric rolling rigid bodies on a horizontal plane. These papers addressed the common misconception that the instantaneous point of contact of the rolling body with the plane can be used to...

We study theoretically the charge density collective oscillations (plasmons) of an extrinsic (i.e., doped) graphene system into which charge carriers (either electrons or holes) are injected. When the injected carriers are sharply peaked so that the distribution function of the injected carriers can be well approximated by finject(p) = ndelta(p - p...

We theoretically study the plasmons (i.e., the charge density collective modes) of a graphene system into which is injected carriers with a sharply peaked distribution function in momentum-space. We find that when this stream of carriers is injected into intrinsic graphene, the collective modes are stable. However, when the stream of carriers is in...

We present data of a one-dimensional collision between a rolling and a stationary golf ball on a rough surface, obtained by video capture using an digital camcorder and analyzed using Logger Pro 3.7 software from Vernier Software and Technology LLC. The collisions appear not to conserve linear momentum. We argue, using conservation of angular momen...

We present derivations of the expressions for the spherical volume averages of static electric and magnetic fields that are virtually identical. These derivations utilize the Coulomb and Biot-Savart laws, and make no use of vector calculus identities or potentials.

We theoretically investigate the possibility of the occurrence of unstable plasma collective modes in graphene (a single layer of carbon atoms in a honeycomb lattice) into which two counter-streaming beams of carriers are injected. The stability of two counter-streaming distributions of carriers is studied by investigating the frequency-dependent d...

We discuss the possibility of the occurrence of plasma instabilities under non-equilibrium conditions in graphene. Specifically, we investigate the stability of the electronic collective modes in graphene with two counter-streaming distributions of carriers by studying the frequency-dependent dielectric function ε(q,phi) of the system. We find that...

Based on relativistic velocity addition and the conservation of momentum and energy, I present simple derivations of the expressions for the relativistic momentum and kinetic energy of a particle, and for the formula E = mc2.

We develop a theory for the renormalization of the phonon energy dispersion in graphene due to the combined effects of both Coulomb and electron-phonon (e-ph) interactions. We obtain the renormalized phonon energy spectrum by an exact analytic derivation of the phonon self-energy, finding three distinct Kohn anomalies (KAs) at the phonon wave vecto...

Mermin has derived the relativistic addition of the parallel components of velocity directly from the constancy of the speed of light. In this note the derivation is extended to the perpendicular components of the velocity.

We calculate the single particle density of states in disordered graphene. For unscreened short-ranged impurities, we use the non-self-consistent and self-consistent Born and $T$-matrix approximations to obtain the self-energy. Among these, only the self-consistent $T$-matrix approximation gives a non-zero density of states at the Dirac point. The...

We develop a theory for the renormalization of the phonon energy dispersion in graphene due to the combined effects of both Coulomb and electron-phonon (e-ph) interactions. We obtain the renormalized phonon energy spectrum by an exact analytic derivation of the phonon self-energy, finding three distinct Kohn anomalies (KAs) at the phonon wavevector...

We discuss the density of states of graphene in the presence of charged screened impurity scattering. The density of states is obtained from the imaginary part of the single-particle Green's function, which is evaluated in the Born and the self-consistent Born approximations, and the screened Coulomb impurity potentials are evaluated within the ran...

We calculate partial differentialmu/ partial differentialn (where mu=chemical potential and n=electron density), which is associated with the compressibility, in graphene as a function of n, within the Hartree-Fock approximation. The exchange-driven Dirac-point logarithmic singularity in the quasiparticle velocity of intrinsic graphene disappears i...

We calculate partial derivative mu/partial derivative n (where mu=chemical potential and n=electron density), which is associated with the compressibility, in graphene as a function of n, within the Hartree-Fock approximation. The exchange-driven Dirac-point logarithmic singularity in the quasiparticle velocity of intrinsic graphene disappears in t...

We discuss the validity (or not) of the ring-diagram approximation (i.e. RPA) in the calculation of graphene self-energy in the weak-coupling ($r_s \ll 1$) limit, showing that RPA is a controlled and valid approximation for \textit{extrinsic} graphene where the Fermi level is away from the Dirac point.

We calculate, within the leading-order dynamical-screening approximation, the electron self-energy and spectral function at zero temperature for extrinsic (or gated/doped) graphene. We also calculate hot carrier inelastic scattering due to electron–electron interactions in graphene. We obtain the inelastic quasiparticle lifetimes and associated mea...

We calculate, within the leading-order dynamical-screening approximation, the electron self-energy and spectral function at zero temperature for extrinsic (or gated/doped) graphene. We also calculate hot carrier inelastic scattering due to electron-electron interactions in graphene. We obtain the inelastic quasiparticle lifetimes and associated mea...

We study the Coulomb drag between two single graphene sheets in intrinsic and extrinsic graphene systems with no interlayer tunneling. The general expression for the nonlinear susceptibility appropriate for single-layer graphene systems is derived using the diagrammatic perturbation theory, and the corresponding exact zero-temperature expression is...

We calculate $\partial\mu/\partial n$ in extrinsic graphene as a function of carrier density $n$ at zero temperature by obtaining the electronic self-energy within the Hartree-Fock approximation. The exchange-driven Dirac-point logarithmic singularity in the quasiparticle velocity of intrinsic graphene disappears in the extrinsic case. The calculat...

The inelastic quasiparticle lifetime of 2D graphene is calculated using the full dynamically screened Coulomb interaction. We calculate the imaginary part of the quasiparticle self-energy for doped (or gated) graphene, using the G0W and random phases approximations. At low energy regimes, the intraband single particle excitation (SPE) and plasmon c...

Mermin [Am. J. Phys. {\bf 51}, 1130--1131 (1983)] derived the relativistic addition of the parallel components of velocity using the constancy of the speed of light. In this note, the derivation is extended to the perpendicular components of velocity.

We consider hot carrier inelastic scattering due to electron--electron interactions in graphene, as functions of carrier energy and density. We calculate the imaginary part of the zero-temperature quasiparticle self-energy for doped graphene, utlizing the $G_0W$ and random phases approximations. Using the full dynamically screened Coulomb interacti...

We study the effects of non-parabolicity of the band-structure and wavevector-dependent scattering rates on the Coulomb drag in coupled quantum wells, using a theoretical formulation that takes these effects into account [K. Flensberg and B. Y.-K. Hu, Phys. Rev. B 52, 14796(1995)]. We examine the conditions in which this formulation reduces to the...

Motivated by recent Coulomb drag experiments in pairs of low-density two-dimensional (2D) electron gases, we investigate the influence of correlation effects on the interlayer drag rate as a function of temperature. We use the self-consistent field method to calculate the intra and interlayer local-field factors Gij(q,T) which embody the short-rang...

We study drag in coupled bilayers where the in-plane mass tensor of one or both layers is anisotropic. We show that the ``transport susceptibility'' F(q,omega) (the central quantity which determines the transresistivity of the bilayer system in the weak interlayer coupling limit; see K. Flensberg and B. Y.-K. Hu, Phys. Rev. B 52, 14796 (1995)) for...

We develop a theory for describing frictional drag in bilayer systems with in-plane periodic potential modulations, and use it to investigate the drag between bilayer systems in which one of the layers is modulated in one direction. At low temperatures, as the density of carriers in the modulated layer is changed, we show that the transresistivity...

Formal solutions to electrostatics boundary-value problems are derived using Green's reciprocity theorem. This method provides a more transparent interpretation of the solutions than the standard Green's function derivation. An energy-based argument for the reciprocity theorem is also presented.

We develop a theory for describing frictional drag in parallel structures with periodic potential modulations, based on the Kubo formalism. The theory is used to investigate drag between two-dimensional systems with potential modulations in one or both layers and one or both directions. We also study drag in modulated quasi-one-dimensional systems....

Submitted to "Notes and Discussions" in American Journal of Physics.

Experiments on drag in coupled quantum wells in the presence of a quantizing perpendicular magnetic field have shown that transresistivities can change sign when the chemical potential of one layer is varied through the Landau level while the other is kept fixed.(X.G. Feng, et al.), Phys. Rev. Lett 81, 3219 (1998). This behavior cannot be understoo...

Interlayer correlations can significantly affect the Coulomb drag signal in coupled quantum wells. Using the -matrix approximation, I consider the Maki–Thompson interlayer correlation effects on the drag rate. The strong interlayer coupling modifies the temperature behavior of the drag rate from the standard weak-coupling T2 result to a more compli...

I give a brief review of the weak coupling theory of frictional drag of the coupled quantum well. I then present a theory of frictional drag based on the Kubo formalism that goes beyond weak coupling. Using the T-matrix approximation, I consider the Maki–Thompson contribution to the transconductivity and obtain a formal result for strong-coupling f...

I investigate the possibility of using Coulomb drag to detect a precursor of the predicted (but as yet not definitively observed) superfluid transition in electron-hole coupled quantum wells. The drag transresisitivity $\rho_{21}$ is shown to be significantly enhanced above the transition temperature $T_c$ and to diverge logarithmically as $T\to T_...

We derive a theory for transmission through disordered finite superlattices in which the interface roughness scattering is treated by disorder averaging. This procedure permits efficient calculation of the transmission thr ough samples with large cross-sections. These calculations can be performed utilizing either the Keldysh or the Landauer-B\"utt...

Independently contacted coupled quantum wells separated by barriers which allow significant interlayer interactions but no tunneling have been fabricated. When current is passed through one layer, the interlayer interactions drag carriers in the second layer, resulting in a voltage response (for open circuits). The magnitude of the response gives a...

We use the Kubo formalism to evaluate the contribution of acoustic phonon exchange to the frictional drag between nearby two-dimensional electron systems. In the case of free phonons, we find a divergent drag rate ($\tau_{D}^{-1}$). However, $\tau_{D}^{-1}$ becomes finite when phonon scattering from either lattice imperfections or electronic excita...

We study phonon-mediated frictional drag between two two-dimensional electron gases. We find two different regimes depending on whether the phonon mean free path ℓph is larger or smaller than a characteristic value . For , the drag is dominated by coupling through an electron–phonon collective mode, whereas for , the drag is mediated by damped phon...

Electron-electron interactions between two closely spaced electron gases can be directly measured by the drag voltage induced in one layer when a current is driven through the other. We have used such drag measurements of GaAs/AlGaAs double quantum wells to probe both the electronic excitations within each layer and the interlayer Coulomb interacti...

We present a theory for inelastic tunneling between a realistic surface and a model spherical STM probe tip, which extends the elastic tunneling work of Tersoff and Hamann. As in the Tersoff-Hamann result, the inelastic current is a function of the local density of states of the adsorbate at the position of the center of the tip. This theory can be...

A first principles theory of inelastic tunneling between a model probe tip and an atom adsorbed on a surface is presented, extending the elastic tunneling theory of Tersoff and Hamann. The inelastic current is proportional to the change in the local density of states at the center of the tip due to the addition of the adsorbate. We use the theory t...

We report STM-induced desorption of H from Si(100)-H(2$\times1$) at negative sample bias. The desorption rate exhibits a power-law dependence on current and a maximum desorption rate at -7 V. The desorption is explained by vibrational heating of H due to inelastic scattering of tunneling holes with the Si-H 5$\sigma$ hole resonance. The dependence...

We theoretically study the electron–electron scattering rate τee−1for electrons in a two-dimensional electron gas with a perpendicular magnetic field, within theGWand plasmon-pole approximations, as functions of temperatureT, impurity scattering rate Γ and magnetic fieldB. The τee−1increases with increasingTand increasing Γ, and shows the structure...

Measurements of momentum transfer between two closely spaced mesoscopic electronic systems, which couple via Coulomb interaction but where tunneling is inhibited, have proven to be a fruitful method of extracting information about interactions in mesoscopic systems. We report a fully microscopic theory for transconductivity σ12, or, equivalently, m...

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...

A treatment of frictional Coulomb drag between two 2-dimensional electron layers in a strong perpendicular magnetic field, within the independent electron picture, is presented. Assuming fully resolved Landau levels, the linear response theory expression for the transresistivity $\rho_{21}$ is evaluated using diagrammatic techniques. The transresis...

At temperatures comparable to the Fermi temperature, we have measured a plasmon enhanced Coulomb drag in a GaAs/AlGaAs double quantum well electron system. This measurement provides a probe of the many-body corrections to the coupled plasmon modes, and we present a detailed comparison between experiment and theory testing the validity of local fiel...

At temperatures comparable to the Fermi temperature, we have measured a plasmon enhanced Coulomb drag in a GaAs/AlGaAs double quantum well electron system. This measurement provides a probe of the many-body corrections to the coupled plasmon modes, and we present a detailed comparison between experiment and theory testing the validity of local fiel...

We study leading-order many-body effects of longitudinal optical (LO) phonons on electronic properties of one-dimensional quantum wire systems. We calculate the quasiparticle properties of a weakly polar one dimensional electron gas in the presence of both electron-phonon and electron-electron interactions. The leading-order dynamical screening app...

We study the transresistivity $\tensor\rho_{21}$ (or equivalently, the drag rate) of two Coulomb-coupled quantum wells in the presence of a perpendicular magnetic field, using semi-classical transport theory. Elementary arguments seem to preclude any possibility of observation of ``Hall drag'' (i.e., a non-zero off-diagonal component in $\tensor\rh...

We use the Kubo formalism to calculate the transresistivity $\rho_{21}$ for carriers in coupled quantum wells in a large perpendicular magnetic field $B$. We find that $\rho_{21}$ is enhanced by approximately 50--100 times over that of the B=0 case in the interplateau regions of the integer quantum Hall effect. The presence of both electron--electr...

We have studied theoretically the Coulomb frictional drag rate of coupled 2-dimensional quantum wells in the presence of a perpendicular magnetic field. In Coulomb drag experiments, a current is applied to one quantum well, and a voltage induced by inter-well Coulomb interactions is measured in the second well. Using a diagrammatic approach to line...

Coulomb interactions lead to many interesting phenomena in low-dimensional systems, one of which is the drag effect in coupled quantum wells.1,2 These experiments involve placing two individually contacted quantum wells close together, driving a current through one layer. This drags the carriers in the second layer along, leading to measurable effe...

We describe a method for numerically incorporating electron--electron scattering in quantum wells for small deviations of the distribution function from equilibrium, within the framework of the Boltzmann equation. For a given temperature $T$ and density $n$, a symmetric matrix needs to be evaluated only once, and henceforth it can be used to descri...

We derive an expression for the drag rate (i.e., interlayer momentum transfer rate) for carriers in two coupled two-dimensional gases to lowest nonvanishing order in the screened interlayer electron--electron interaction, valid for {\sl arbitrary} intralayer scattering mechanisms, using the Boltzmann transport equation. We calculate the drag rate f...

We report a fully microscopic theory for transconductivity, or, equivalently, momentum transfer rate, of Coulomb coupled electron systems. We use the Kubo linear response formalism, and our main formal result expresses the transconductivity in terms of two fluctuation diagrams, which are topologically related, but not equivalent to, the Aslamazov-L...

Using a finite-frequency recursive Green's function technique, we calculate the dynamic magneto-conductance fluctuations and oscillations in disordered mesoscopic normal metal systems, incorporating inter-particle Coulomb interactions within a self-consistent potential method. In a disordered metal wire, we observe ergodic behavior in the dynamic c...

We show theoretically that the Coulomb drag rate between two parallel quasi-two-dimensional electron gases is substantially enhanced by the coupled acoustic and optic plasmon modes of the system at temperatures $T \gtrsim 0.2T_F$ (where $T_F$ is the Fermi temperature) for experimentally relevant parameters. The acoustic mode causes a sharp upturn i...

We show that, for doped semiconductor structures at nonzero temperatures, processes which scatter electrons into a state ||k> can contribute strongly to the decay of a nonequilibrium electron occupation of ||k>. For electrons, the decay rate gamma(k) is given by the sum of the total scattering-out and scattering-in rates of state ||k>. The scatteri...

We calculate the electron elastic mean free path due to ionized impurity scattering in semiconductor quantum wires, using a scheme in which the screened ionized impurity potential and the electron screening self-consistently determine each other. By using a short-range-scattering potential model, we obtain an exact solution of the self-energy withi...

We consider theoretically the electron–electron interaction induced exchange-correlation effects in the lowest subband of a quasi-one-dimensional GaAs quantum wire structures. We calculate, within the leading order dynamical screening approximation (i.e. the so-called GW approximation of the electron gas theory), the electron self-energy, spectral...

Using a simple contour deformation method it is shown that there is a very general relationship between imaginary-time correlation functions and real-time commutators. This method is used to show easy derivations of the equivalence between (1) two dissimilar forms of the Kubo formula for the electrical conductivity tensor sigmamunu(omega), and (2)...

We consider theoretically the electron--electron interaction induced exchange-correlation effects in the lowest subband of a quasi-one-dimensional GaAs quantum wire structures. We calculate, within the leading order dynamical screening approximation ({\em i.e.} the so-called $GW$ approximation of the electron gas theory), the electron self-energy,...

We present a method for obtaining expressions for the analytic continuation of finite-temperature self-energies which are suitable for use in numerical computations. In the case of the GW approximation for the self-energy, this method gives the finite-temperature generalization of the zero-temperature ‘‘line and pole’’ decomposition. This formalism...

We review the many-body exchange-correlation properties of electrons confined to the lowest sub-band of a quantum wire, including effects of impurity scattering. Without impurity scattering, the virtual excitations of arbitrarily low energy one-dimensional plasmons destroy the Fermi surface of the electrons, whereas the presence of impurity scatter...

We calculate finite temperature inelastic scattering rates and mean free paths of electrons injected into a quantum wire containing a quasi‐one‐dimensional electron gas. We show that there is a very sharp increase in the electron scattering rate at the one‐dimensional plasmon emission threshold. Based on these results, we suggest the possibility of...

We calculate finite temperature inelastic scattering rates and mean free paths of electrons injected into a quantum wire containing a quasi-one-dimensional electron gas. We show that there is a very sharp increase in the electron scattering rate at the one-dimensional plasmon emission threshold. Based on these results, we suggest the possibility of...

We study the many-body exchange-correlation properties of electrons confined to the lowest subband of a quantum wire, including effects of impurity scattering. Without impurity scattering, virtual excitations of arbitrarily low-energy plasmons destroy the Fermi surface of the electrons, whereas the presence of impurity scattering damps out these pl...

We calculate the finite temperature inelastic scattering rate for hot electrons injected into n-doped GaAs for various doping densities and injected electron energies. We use the Born approximation and treat the base region as a three-dimensional coupled electron-phonon system, so that the Coulomb and Frohlich interactions with the injected electro...

Using the Boltzmann equation, we study the collective modes of a photoexcited electron-hole plasma in a direct-gap, small-electron-mass semiconductor in which the electron distribution is evolving with time. In this situation, we find that there exists an acoustic mode of the electron-hole plasma with a time-dependent hase velocity. The phase veloc...

We calculate, using the Born approximation, the finite-temperature scattering rate for hot electrons injected into n-type doped GaAs for various doping densities and injected-electron energies. We treat the base region as a three-dimensional coupled electron-phonon system, so that the Coulomb and Fröhlich interactions with the injected electron are...

We employ the linear-response theory of collisionless plasmas and the linear-response theory of carriers in a static, homogeneous electric field, with collisions approximated by the relaxation-time approximation [Phys. Rev. B 39, 8464 (1989)] to study instabilities with respect to charge-density perturbations of counterstreaming charged particles....

The quantum-transport-equation approach, which was used to calculate nonequilibrium screening in the nondegenerate regime [Phys. Rev. B 39, 8468 (1989)], is extended to study nonequilibrium screening in the highly degenerate regime. We obtain an expression for the nonequilibrium electric susceptibility χ(q,ω)=δn(q,ω)/δU(q,ω) for a degenerate system...

A short derivation of the Kramers-Kronig relations is presented.

Linear screening in strongly nonequilibrium semiconductors is studied by a Boltzmann-equation approach. In determining the nonequilibrium susceptibility χ(q,ω), the correct distribution function is used, and the effects of scattering are included. As an application, we find that the ionized-impurity–scattering rate in a bulk semiconductor is signif...

The Kadanoff-Baym formulation of quantum transport is used to derive a formulation for non- equilibrium carrier screening. The approach extends the Boltzmann-equation approach for calculating carrier-screening phenomena to include quantum effects due to the spatial nonlocality of the electron. To simplify calculations, the quantum relaxation-time a...

Surface plasmons are charge density waves bound to the interface between a dielectric and a conducting medium. A periodically modulated interface, such as a metallic diffraction grating, causes plasmons to Bragg reflect, thus introducing Brillouin zones into the surface plasmon dispersion relation, and causes non-radiative surface plasmons to coupl...

Acoustic-phonon (AP) mediated frictional drag between electrons in parallel two-dimensional electron layers has been experimentally observed at low temperatures (T ≈ 4 K) in GaAs quantum wells, in spite of the small electron--AP coupling constants. The optical-phonon (OP) coupling constants are considerably larger in III-V materials, so one migh...

We theoretically examine drag in coupled silicon bilayers. The unique feature of n-type silicon compared to GaAs, the material commonly used in bilayer drag experiments, is that the Fermi surface of n-type silicion consists of several anisotropic Â"pockets,Â" compared to a single spherical Fermi surface in GaAs. We show that the Â"transport polariz...