Electron-Spin and Electron-Orbital Dependence of the Tunnel Coupling in Laterally Coupled Double Vertical Dots

Abstract

We employ a new laterally coupled, vertical double dot with a tunable tunnel-coupling gate in a parallel configuration to study the electron spin and orbital dependence of quantum mechanical tunnel coupling on the size of the honeycomb vertices in the small electron numbers regime. We find a transition from the weak coupling regime, where fluctuations in tunnel coupling due to varying electron configuration dominate the anticrossings, to a regime where the two dots coalesce. We apply a magnetic field to ascertain the orbital angular momenta of the Fermi surface eigenstates, which correlate with anticrossing size, and we identify spin pairs with congruent behavior.

Connection between noise and quantum correlations in a double quantum dot

“…Adding a second electron, we first have to overcome the gate voltage again, and additionally the repulsive Coulomb interaction be-tween the two electrons leads to a spin-dependent splitting of the eigenenergies. For the singlet state ͉S͘ we obtain the energy E S =2eV g + u 12 − J, and for the ͑threefold degenerate͒ triplet state ͉T͘ the energy E T =2eV g + u 12 . Here, u 12 is the ͑interdot͒ electron-electron repulsion and J =4t 0 2 / u H is the Heisenberg exchange parameter that characterizes the Heisenberg interaction between the two spins, H spin = JS 1 · S 2 ; u H is the on-site Coulomb repulsion.…”

“…This is one of the motivations to study double quantum dots. [4][5][6][7][8][9][10][11][12][13] In particular, it is required to create entangled electron states by the interaction of an electron inside the double dot with an electron tunneling onto the double dot. Measuring this entanglement is an important experimental task, and theoretical suggestions on how to probe these states are needed.…”

Electronic structure of multiple dots

“…73.21.La; 03.67.Lx; 71.15.Mb The spin state of electrons in multiple quantum dot assemblies formed in two dimensional electron gas (2DEG) semiconductor heterostructures is determined by exchange interactions between the electrons and not, generally, by the much smaller magnetic dipole interactions between the spins. In the simplest case of two electrons in two dots (artificial molecular hydrogen) competition between exchange, which favors spin alignment (spin triplet), and tunneling, which delocalizes the electrons and tends [1] to favor spin anti-alignment (spin singlet) can be modulated by a magnetic field and is sensitive to the precise geometric nature of the tunnel barrier separating the two dots [2]. The exchange splitting J is defined as the energy difference between the ground state triplet and the ground state singlet (and is distinct from the exchange integral which is one of the Coulomb matrix elements between two-electron states) and is crucial to the implementation of various schemes of quantum computation [3].…”

Theory of a two-level artificial molecule in laterally coupled quantum Hall droplets

“…There is currently significant experimental 1,2,3,4,5,6,7,8,9,10,11,12 and theoretical 13,14,15,16,17,18,19,20,21,22,23 interest in coupled lateral quantum dots. The main effort is on developing means of control of quantum mechanical coupling of artificial molecules, with each dot playing the role of an artificial atom 5,6,7,13 .…”