![]() ![]() GHz upon the WM formation 27, 29 because of strong electron–electron interactions confirmed by full-configuration interaction (FCI)-based theories 23, 25, 28, 30.It has been demonstrated that the E ST can reach down to ~10 0 h Recent studies on QDs in various systems have shown clear evidence of WM formation 22, 23, 25, 26, 27, 28, 29. GHz h is Planck’s constant) in particular in GaAs limits the access to higher spin states 20 in multielectron QDs at moderate external magnetic fields B 0 ![]() Despite the versatility of gate-defined QD systems 16, 17, 18, 19, the large singlet–triplet energy splitting E ST (~10 2 h However, spin qubit control combined with DNP has been limited to two-electron singlet–triplet (ST 0) spin qubits 9, 10, 11, 12, 15. Because the qubit control typically requires small QD-reservoir tunnel rates transition from the pulsed-gate DNP to qubit experiments is straightforward without additional parameter modulation via the gate voltages. On the contrary, the DNP based on the pulsed-gate technique can be demonstrated while maintaining the small tunnel rates ~10 1 kHz. While the DNP achieved by spin-flip mediated transport with an applied bias 13, 14 allows large DNP 13, the QD - reservoir tunnel rate needs to be large enough to allow the finite spin-flip current. Gate-defined semiconductor QDs have been used to achieve the fast probing of nuclear environments 8, 11, 12, bidirectional DNP 11, and active feedback control of nuclear fields 10. DNP is used for enhancing the signal-to-noise ratio in nuclear magnetic resonance 6 and prolonging coherence times in QD-based spin qubits 9, 10. Although the fluctuation of nuclear fields, which is quantified by the effective Overhauser field B nuc 3, 4, often acts as a magnetic-noise source for spin qubits 3, the hyperfine electron–nuclear spin interaction allows achieving dynamic nuclear polarization (DNP) 5, 6, 7, 8. Semiconductor quantum dot (QD) systems facilitate investigations of the interaction between electron spins and nuclear environments, which is known as the central-spin problem 1, 2. Thus, we confirm the spin structure of a WM, paving the way for active control of correlated electron states for application in mesoscopic environment engineering. We demonstrate that the same level of control cannot be achieved in the non-interacting regime. Combined with coherent control of spin states, we achieve control of magnitude, polarity, and site dependence of the nuclear field. A Landau–Zener sweep-based polarization sequence and low-lying anticrossings of spin multiplet states enabled by Wigner-molecularization are utilized. Here, we demonstrate efficient control of spin transfer between an artificial three-electron WM and the nuclear environment in a GaAs double QD. Although Wigner-molecularization has been confirmed by real-space imaging and coherent spectroscopy, the open system dynamics of the strongly correlated states with the environment are not yet well understood. Multielectron semiconductor quantum dots (QDs) provide a novel platform to study the Coulomb interaction-driven, spatially localized electron states of Wigner molecules (WMs).
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