The ordinary Hall effect is driven by the Lorentz force, while its anomalous counterpart occurs in ferromagnets. Here we show that the Berry curvature monopole of non-magnetic 2D spin-3/2 holes leads to a novel Hall effect linear in an applied in-pla
ne magnetic field B_x. There is no Lorentz force hence no ordinary Hall effect, while all disorder contributions vanish to leading order in B_x. This intrinsic phenomenon, which we term the anomalous planar Hall effect (APHE), provides a non-quantized footprint of topological transport directly accessible in p-type semiconductors.
Strong spin-orbit interactions make hole quantum dots central to the quest for electrical spin qubit manipulation enabling fast, low-power, scalable quantum computation. Yet it is important to establish to what extent spin-orbit coupling exposes qubi
ts to electrical noise, facilitating decoherence. Here, taking Ge as an example, we show that group IV gate-defined hole spin qubits generically exhibit optimal operation points, defined by the top gate electric field, at which they are both fast and long-lived: the dephasing rate vanishes to first order in electric field noise along all directions in space, the electron dipole spin resonance strength is maximised, while relaxation is drastically reduced at small magnetic fields. The existence of optimal operation points is traced to group IV crystal symmetry and properties of the Rashba spin-orbit interaction unique to spin-3/2 systems. Our results overturn the conventional wisdom that fast operation implies reduced lifetimes, and suggest group IV hole spin qubits as ideal platforms for ultra-fast, highly coherent scalable quantum computing.
Semiconductor holes with strong spin-orbit coupling allow all-electrical spin control, with broad applications ranging from spintronics to quantum computation. Using a two-dimensional hole system in a GaAs quantum well, we demonstrate a new mechanism
of electrically controlling the Zeeman splitting, which is achieved through altering the hole wave vector $k$. We find a threefold enhancement of the in-plane $g-$factor $g_{parallel}(k)$. We introduce a new method for quantifying the Zeeman splitting from magnetoresistance measurements, since the conventional tilted field approach fails for two-dimensional systems with strong spin-orbit coupling. Finally, we show that the Rashba spin-orbit interaction suppresses the in-plane Zeeman interaction at low magnetic fields. The ability to control the Zeeman splitting with electric fields opens up new possibilities for future quantum spin-based devices, manipulating non-Abelian geometric phases, and realising Majorana systems in $p-$type superconductor systems.
With a view to electrical spin manipulation and quantum computing applications, recent significant attention has been devoted to semiconductor hole systems, which have very strong spin-orbit interactions. However, experimentally measuring, identifyin
g, and quantifying spin-orbit coupling effects in transport, such as electrically-induced spin polarizations and spin-Hall currents, are challenging. Here we show that the magnetotransport properties of two dimensional (2D) hole systems display strong signatures of the spin-orbit interaction. Specifically, the low-magnetic field Hall coefficient and longitudinal conductivity contain a contribution that is second order in the spin-orbit interaction coefficient and is non-linear in the carrier number density. We propose an appropriate experimental setup to probe these spin-orbit dependent magnetotransport properties, which will permit one to extract the spin-orbit coefficient directly from the magnetotransport.
Spin-orbit coupling is key to all-electrical control of quantum-dot spin qubits, and is frequently stronger for holes than for electrons. Here we investigate Pauli spin blockade for two heavy holes in a gated double quantum dot in an in-plane magneti
c field. The interplay of the complex Zeeman and spin-orbit couplings causes a blockade leakage current anisotropic in the field direction. The period of the anisotropic leakage is critically dependent on the relative magnitude of Zeeman interaction terms linear and cubic in the magnetic field. The current and singlet-triplet exchange splitting can be effectively adjusted by an appropriate choice of field direction, providing a simple control variable for quantum information processing and a way of tailoring magnetic interactions in hole spin qubits.
