Nodal ground states and orbital textures in semiconductor quantum dots

Abstract

Conventional understanding implies that the ground state of a nonmagnetic quantum mechanical system should be nodeless. While this notion also provides a valuable guidance in understanding the ordering of energy levels in semiconductor nanostructures, there are reports that nodal ground states for holes are possible. However, the existence of such nodal states has been debated and even viewed merely as an artifact of a k·p model. Using complementary approaches of both k·p and tight-binding models, further supported by an effective Hamiltonian for a continuum model, we reveal that nodal ground states in quantum dots are not limited to a specific approach. Remarkably, the emergence of nodal hole states at the top of the valence band can be attributed to the formation of orbital vortex textures through competition between the hole kinetic energy and the coupling to the conduction band states. We suggest an experimental test for our predictions of the reversed energy ordering and the existence of nodal ground states. We discuss how our findings and the studies of orbital textures could be also relevant for other materials systems.

Toward high-frequency operation of spin lasers

“…Their effective mass parameters are connected bỹ γ 1 = γ 1 − E P /3E g γ 2 = γ 2 − E P /6E g γ 3 = γ 3 − E P /6E g A = 1 m * e − E g + 2 3 ∆ SO E g + ∆ SO E P E g E P = 2m 0 P 2 / 2 , (A-6) whereγ 1,2,3 are used in the 8×8 model and γ 1,2,3 in the 6×6 model, which can also be related to the tight-binding parameters. 91 To recover the 6×6 model from the 8×8 model, we set P = 0 in Eqs. (A-3), (A-4) and (A-6).…”

Time-resolved magnetophotoluminescence studies of magnetic polaron dynamics in type-II quantum dots

“…41,42 In the first case (single magnetic ion), such systems could be considered as potential quantum bits, quantum memories, or probes to detect an unconventional orbital ordering. 17,[23][24][25]43 In the second case, the presence of several magnetic ions can lead to the formation of a magnetic polaron (MP), a long-standing research topic in magnetic semiconductors. [5][6][7][8]44 MP can be viewed as a cluster of localized magnetic ion spins, aligned through an exchange interaction with the spin of a confined carrier.…”

Ground state of an exciton in a three-dimensional parabolic quantum dot: Convergent perturbative calculation

“…and work in the strong-confinement regime [28] with small parameter α. Regardless of the V -split, the ground state wave function, ψ (here assumed to be nodeless; for the possibility of having a nodal ground state see [31]), is sought in the form…”