Disentangling orbital and confinement contributions to $g$ -factor in Ge/SiGe hole quantum dotsDisentangling orbital and confinement contributions to $g$-factor in Ge/SiGe hole quantum dots

L. Sommer, I. Seidler, F. J. Schupp +12 more

Spin qubits are typically operated in the lowest orbital of a quantum dot to minimize interference from nearby states. In valence-band hole systems, strong spin-orbit coupling links spin and orbital degrees of freedom, strongly influencing the hole $g$ -factor, a key parameter for qubit control. We investigate the out-of-plane $g$ -factor in Ge quantum dots using excitation (single-particle) and addition (many-body) spectra. Excitation spectra allow us to distinguish the pure Zeeman $g$ -factor from orbital contributions to the magnetic field splitting of states despite the strong spin-orbit coupling. This distinction clarifies discrepancies between $g$ -factors extracted with the two methods, for different orbital states and different hole numbers. Furthermore, we find gate-tunability of $g$ -factors at the level of 15%, highlighting its relevance for all-electric qubit manipulation.Spin qubits are typically operated in the lowest orbital of a quantum dot to minimize interference from nearby states. In valence-band hole systems, strong spin-orbit coupling links spin and orbital degrees of freedom, strongly influencing the hole $g$-factor, a key parameter for qubit control. We investigate the out-of-plane $g$-factor in Ge quantum dots using excitation (single-particle) and addition (many-body) spectra. Excitation spectra allow us to distinguish the pure Zeeman $g$-factor from orbital contributions to the magnetic field splitting of states despite the strong spin-orbit coupling. This distinction clarifies discrepancies between $g$-factors extracted with the two methods, for different orbital states and different hole numbers. Furthermore, we find gate-tunability of $g$-factors at the level of 15%, highlighting its relevance for all-electric qubit manipulation.

cond-mat.mes-hallCross-listedarXiv:2602.09913Feb 11, 2026

Creation of entangled exciton states in coupled quantum dots

Celestino Creatore, Richard Brierley, R. T. Phillips +2 more

Bulletin of the American Physical SocietyFeb 29, 20120 citations

Block excitonic condensate at n=3.5 in a spin-orbit coupled t2g multiorbital Hubbard model

Nitin Kaushal, Alberto Nocera, Gonzalo Álvarez +2 more

Theoretical studies recently predicted the condensation of spin-orbit excitons at momentum $q=\ensuremath{\pi}$ in ${t}_{2g}^{4}$ spin-orbit coupled three-orbital Hubbard models at electronic density $n=4$ . In parallel, experiments involving iridates with noninteger valence states for the Ir ions are starting to attract considerable attention. In this publication, using the density matrix renormalization group technique we present evidence for the existence of an excitonic condensate at $n=3.5$ in a one-dimensional Hubbard model with a degenerate ${t}_{2g}$ sector, when in the presence of spin-orbit coupling. At intermediate Hubbard $U$ and spin-orbit $\ensuremath{\lambda}$ couplings, we found an excitonic condensate at the unexpected momentum $q=\ensuremath{\pi}/2$ involving ${j}_{\mathrm{eff}}=3/2,m=\ifmmode\pm\else\textpm\fi{}1/2$, and ${j}_{\mathrm{eff}}=1/2,m=\ifmmode\pm\else\textpm\fi{}1/2$ bands in the triplet channel, coexisting with an also unexpected block magnetic order. We also present the entire $\ensuremath{\lambda}$ vs $U$ phase diagram, at a fixed and robust Hund coupling. Interestingly, this new ``block excitonic phase'' is present even at large values of $\ensuremath{\lambda}$, unlike the $n=4$ excitonic phase discussed before. Our computational study helps to understand and predict the possible magnetic phases of materials with ${d}^{3.5}$ valence and robust spin-orbit coupling.Theoretical studies recently predicted the condensation of spin-orbit excitons at momentum $q=\ensuremath{\pi}$ in ${t}_{2g}^{4}$ spin-orbit coupled three-orbital Hubbard models at electronic density $n=4$. In parallel, experiments involving iridates with noninteger valence states for the Ir ions are starting to attract considerable attention. In this publication, using the density matrix renormalization group technique we present evidence for the existence of an excitonic condensate at $n=3.5$ in a one-dimensional Hubbard model with a degenerate ${t}_{2g}$ sector, when in the presence of spin-orbit coupling. At intermediate Hubbard $U$ and spin-orbit $\ensuremath{\lambda}$ couplings, we found an excitonic condensate at the unexpected momentum $q=\ensuremath{\pi}/2$ involving ${j}_{\mathrm{eff}}=3/2,m=\ifmmode\pm\else\textpm\fi{}1/2$, and ${j}_{\mathrm{eff}}=1/2,m=\ifmmode\pm\else\textpm\fi{}1/2$ bands in the triplet channel, coexisting with an also unexpected block magnetic order. We also present the entire $\ensuremath{\lambda}$ vs $U$ phase diagram, at a fixed and robust Hund coupling. Interestingly, this new ``block excitonic phase'' is present even at large values of $\ensuremath{\lambda}$, unlike the $n=4$ excitonic phase discussed before. Our computational study helps to understand and predict the possible magnetic phases of materials with ${d}^{3.5}$ valence and robust spin-orbit coupling.

arXiv:1901.05578Physical review. B./Physical review. BApr 8, 20196 citations

Influences of strong exciton–phonon interaction on two coupled quantum dots within cavity QED

Xiao-Zhong Yuan, Ka‐Di Zhu, Wai-Sang Li

Physics Letters AAug 1, 200411 citations

On the upper limit for optical spin pumping in III-V semiconductor quantum dots

Boris M. Vulović, Igor Ovchinnikov, K.L. Wang

We studied the optical steady-state generation of spin in the III-V semiconductor quantum dots, where an external laser field couples to the quantum dot only via the electric dipole interband transition and generation of spin in the conduction band is due to the optical transition from the spin-split valence band. In the weak field regime, the optical spin generation is second order in the Rabi frequency. At the intense laser fields, the spin-orbit interaction is of no importance and the optical spin generation is absent. Therefore, there should be a region featured by intermediate Rabi frequencies where the optical spin generation reaches its maximum. We demonstrated this upper limit using a simple model of the III-V quantum dot. The maximum corresponds to the optical interaction energy equal to the spin-orbit interaction energy in the valence band. The work addressed here sets the upper limit for steady-state optical spin generation in the III-V semiconductor quantum dots and completes the physical picture of this process for all optical field strengths.We studied the optical steady-state generation of spin in the III-V semiconductor quantum dots, where an external laser field couples to the quantum dot only via the electric dipole interband transition and generation of spin in the conduction band is due to the optical transition from the spin-split valence band. In the weak field regime, the optical spin generation is second order in the Rabi frequency. At the intense laser fields, the spin-orbit interaction is of no importance and the optical spin generation is absent. Therefore, there should be a region featured by intermediate Rabi frequencies where the optical spin generation reaches its maximum. We demonstrated this upper limit using a simple model of the III-V quantum dot. The maximum corresponds to the optical interaction energy equal to the spin-orbit interaction energy in the valence band. The work addressed here sets the upper limit for steady-state optical spin generation in the III-V semiconductor quantum dots and completes the physical picture of this process for all optical field strengths.

Journal of Applied PhysicsMar 15, 20113 citations

Disentangling orbital and confinement contributions to

g

-factor in Ge/SiGe hole quantum dots

g

-factor, a key parameter for qubit control. We investigate the out-of-plane

g

-factor in Ge quantum dots using excitation (single-particle) and addition (many-body) spectra. Excitation spectra allow us to distinguish the pure Zeeman

g

-factor from orbital contributions to the magnetic field splitting of states despite the strong spin-orbit coupling. This distinction clarifies discrepancies between

g

-factors extracted with the two methods, for different orbital states and different hole numbers. Furthermore, we find gate-tunability of

g

-factors at the level of 15%, highlighting its relevance for all-electric qubit manipulation.

Theoretical studies recently predicted the condensation of spin-orbit excitons at momentum $q=\ensuremath{\pi}$ in

{t}_{2g}^{4}

spin-orbit coupled three-orbital Hubbard models at electronic density

n=4

. In parallel, experiments involving iridates with noninteger valence states for the Ir ions are starting to attract considerable attention. In this publication, using the density matrix renormalization group technique we present evidence for the existence of an excitonic condensate at

n=3.5

in a one-dimensional Hubbard model with a degenerate

{t}_{2g}

sector, when in the presence of spin-orbit coupling. At intermediate Hubbard

U

and spin-orbit $\ensuremath{\lambda}$ couplings, we found an excitonic condensate at the unexpected momentum $q=\ensuremath{\pi}/2$ involving ${j}_{\mathrm{eff}}=3/2,m=\ifmmode\pm\else\textpm\fi{}1/2$, and ${j}_{\mathrm{eff}}=1/2,m=\ifmmode\pm\else\textpm\fi{}1/2$ bands in the triplet channel, coexisting with an also unexpected block magnetic order. We also present the entire $\ensuremath{\lambda}$ vs

U

phase diagram, at a fixed and robust Hund coupling. Interestingly, this new ``block excitonic phase'' is present even at large values of $\ensuremath{\lambda}$, unlike the

n=4

excitonic phase discussed before. Our computational study helps to understand and predict the possible magnetic phases of materials with

{d}^{3.5}

valence and robust spin-orbit coupling.