Search results for "mesoscopic"
showing 10 items of 709 documents
Spin-layer locking of interlayer excitons trapped in moir\'e potentials
2019
Van der Waals heterostructures offer attractive opportunities to design quantum materials. For instance, transition metal dichalcogenides (TMDs) possess three quantum degrees of freedom: spin, valley index, and layer index. Further, twisted TMD heterobilayers can form moir\'e patterns that modulate the electronic band structure according to atomic registry, leading to spatial confinement of interlayer exciton (IXs). Here we report the observation of spin-layer locking of IXs trapped in moir\'e potentials formed in a heterostructure of bilayer 2H-MoSe$_2$ and monolayer WSe$_2$. The phenomenon of locked electron spin and layer index leads to two quantum-confined IX species with distinct spin-…
Phenomenology of current-skyrmion interactions in thin films with perpendicular magnetic anisotropy
2014
We study skyrmions in magnetic thin films with structural inversion asymmetry perpendicular to the film plane. We determine the magnetization texture of a single skyrmion and its dependence on the strength of the Dzyaloshinskii-Moriya interaction relative to the magnetostatic energy. Furthermore, we construct a phenomenological model that describes the interaction between the motion of skyrmions and electric currents to lowest order in spin-orbit coupling. We estimate the experimental verifiable velocities for current-driven motion of skyrmion textures based on available results obtained from domain walls dynamics.
Electron-phonon interaction in thin copper and gold films
2004
We have studied the electron-phonon (e-p) interaction in thin Cu and Au films at sub-Kelvin temperatures with the help of the hot electron effect, using symmetric normal metal-insulator-superconductor tunnel junction pairs as thermometers. By Joule heating the electron gas and measuring the electron and the lattice temperatures simultaneously, we show that the electron-phonon scattering rate follows a $T^{4}$ temperature dependence in both metals. The result is in accordance with the theory of e-p scattering in disordered films with vibrating boudaries and impurities, in contrast to the $T^{3}$-law expected for pure samples, and $T^{2}$-law for static disorder.
Large diamagnetic persistent currents
2007
In multichannel rings, evanescent modes will always co-exist with propagating modes. The evanescent modes can carry a very large diamagnetic persistent current that can oscillate with energy and are very sensitive to impurity scattering. This provides a natural explanation for the large diamagnetic persistent currents observed in experiments.
Quantitative modeling of spin relaxation in quantum dots
2011
Physics Department, Harvard University, 02138 Cambridge MA, USA(Dated: December 16, 2011)We use numerically exact diagonalization to calculate the spin-orbit and phonon-induced triplet-singlet relaxation rate in a two-electron quantum dot exposed to a tilted magnetic field. Our schemeincludes a three-dimensional description of the quantum dot, the Rashba and the linear and cubicDresselhaus spin-orbit coupling, the ellipticity of the quantum dot, and the full angular descriptionof the magnetic field. We are able to find reasonable agreement with the experimental results ofMeunier et al. [Phys. Rev. Lett. 98, 126601 (2007)] in terms of the singlet-triplet energy splittingand the spin relaxation …
Temperature dependence of the effective mobility edge and recombination dynamics of free and localized excitons in InGaP/GaAs quantum wells
2003
3 páginas, 1 figura.-- Comunicación presentada al Proceedings of the International Conference on Superlattices, Nano-structures and Nano-devices ICSNN 2002 o-structures and Nano-devices ICSNN 2002.
Gaussian quantum dots of type II in in-plane electric field
2007
The growing interest is recently focusing on QDs of type II, which contrary to type I QDs attract electrons and repulse holes (or conversely). In such QDs an electron-hole pair (Xexciton) can still be traped due to electron-hole Coulomb attraction, resulting in significantly more complex structure of excitonic states. We consider an X exciton in QD of type II defined by electrostatic focusing in a narrow quantum well, in the presence of additional external in-plane electric field. The dependence of PL spectrum on dot size and in-plane electric field is analysed within the Hartree approach for model planar Gaussian confinement. The exciton ground state and its energy red-shift are found as a…
Lateral induced dipole moment and polarizability of excitons in a ZnO single quantum disk
2013
The lateral Stark shift of an exciton confined in a single ZnO quantum thin disk of radius R was calculated using a variational approach within the two bands effective mass approximation. It is shown that the exciton has a non negligible induced dipole moment when an external electric field is applied mainly for electron-hole separation below to the 3D excitonic Bohr radius. The behavior of the exciton lateral Stark shift proves the existence of an important correlation between the polarizability and the induced dipole moment.
Thermometry by Arrays of Tunnel Junctions
1994
We show that arrays of tunnel junctions between normal metal electrodes exhibit features suitable for primary thermometry in an experimentally adjustable temperature range where thermal and charging effects compete. $I\ensuremath{-}V$ and $\frac{\mathrm{dI}}{\mathrm{dV}}$ vs $V$ have been calculated for two junctions including a universal analytic high temperature result. Experimentally the width of the conductance minimum in this regime scales with $T$ and $N$, the number of junctions, and its value (per junction) agrees with the calculated one to within 3% for large $N$. The height of this feature is inversely proportional to $T$.
Spin transport in ferromagnetic/normal-metal tunnel junction arrays
2012
Published version of an article in the journal: Physical Review B. Also available from the publisher:http://dx.doi.org/10.1103/PhysRevB.85.094421 An array of alternating ferromagnetic and normal-metal islands separated by small tunnel junctions is theoretically investigated in the sequential tunneling regime. A numerical Monte Carlo method is used to calculate the transport properties. The spin-dependent tunneling currents give rise to nonequilibrium spin accumulation on the normal island. The tunneling magneto resistance (TMR) is calculated for a large range of array parameters. The TMR oscillates with bias voltage and can become negative for certain array parameters. We show that the long…