Effective out-of-plane g-factor in strained-Ge/SiGe quantum dots

Miller, Andrew J.; Brickson, Mitchell; Hardy, Will; Liu, Chia-You; Li, Jiun-Yun; Baczewski, Andrew David; Lilly, Michael; Lu, Tzu-Ming; Luhman, Dwight

doi:10.48550/arxiv.2102.01758

Cited by 3 publications

(3 citation statements)

References 9 publications

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“…The p-type nature of the valence band leads to a mixing of the orbital and spin degrees of freedom of the carriers, yielding a potentially strong effective SOI that depends on the details of the confinement. This can give rise to several interesting phenomena such as a highly anisotropic and electrically tunable g-tensor [35][36][37][38][39][40][41][42][43][44][45][46], and it could also allow for very fast spin-qubit manipulation [47][48][49][50][51][52][53].…”

Section: Introductionmentioning

confidence: 99%

Probing details of spin--orbit coupling through Pauli spin blockade

Qvist¹,

Danon²

2022

Preprint

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Spin-orbit interaction (SOI) plays a fundamental role in many low-dimensional semiconductor and hybrid quantum devices. In the rapidly evolving field of semiconductor spin qubits, SOI is an essential ingredient that can allow for ultrafast qubit control. The exact manifestation of SOI in a given device is, however, often both hard to predict theoretically and probe experimentally. Here, we develop a detailed theoretical connection between the leakage current through a double quantum dot in Pauli spin blockade and the underlying SOI in the system. We present a general analytic expression for the leakage current, which allows to connect experimentally observable features to both the magnitude and orientation of the effective spin-orbit field acting on the moving carriers. Motivated by the large recent interest in hole-based quantum devices, we further zoom in on the case of Pauli blockade of hole spins, assuming a strong transverse confinement potential. In this limit we also find an analytic expression for the current at low external magnetic field, that includes the effect of hyperfine coupling of the hole spins to randomly fluctuating nuclear spin baths. This result can be used to extract detailed information about both hyperfine and spin-orbit coupling parameters for hole spins in devices with a significant fraction of non-zero nuclear spins.

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Section: Introductionmentioning

confidence: 99%

Probing details of spin--orbit coupling through Pauli spin blockade

Qvist¹,

Danon²

2022

Preprint

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“…15 Hole spin qubits in Ge/SiGe, in contrast to electron spin qubits, have the capability of all-electric control of the hole spin through strong intrinsic spin orbit coupling, 16 and exhibit tunable, 14 anisotropic g-factors. 17 Together these features open the possibility for simplified and flexible control features in the qubit platform.…”

Section: Introductionmentioning

confidence: 99%

Thermal activation of low-density Ga implanted in Ge

Foster,

Miller,

Hutchins-Delgado

et al. 2022

Preprint

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The nuclear spins of low-density implanted Ga atoms in Ge are interesting candidates for solid state-based qubits. To date, activation studies of implanted Ga in Ge have focused on high densities. Here we extend activation studies into the low-density regime. We use spreading resistance profiling and secondary ion mass spectrometry to derive electrical activation of Ga ions implanted into Ge as a function of rapid thermal anneal temperature and implant density. We show that for our implant conditions the activation is best for anneal temperatures between 400 and 650 • C, with a maximum activation of 64% at the highest fluence. Below 400 • C, remaining implant damage results in defects that act as superfluous carriers, and above 650 • C, surface roughening and loss of Ga ions are observed. The activation increased monotonically from 10% to 64% as the implant fluence increased from 6 × 10 10 to 6 × 10 12 cm −2 . The results provide thermal anneal conditions to be used for initial studies of using low-density Ga atoms in Ge as nuclear spin qubits.

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“…Recent experiments on two-dimensional hole quantum wells and quantum dots have indeed shown wildly varying and anisotropic effective hole masses [38][39][40] and gfactors [41][42][43][44][45][46][47][48][49][50][51][52], depending on choice of material, hole densities, and on the details of the confinement. In this paper we theoretically investigate these anisotropic properties of confined holes in detail, with a focus on the role of the precise orientation of the confinement potentials with respect to the crystal orientation.…”

Section: Introductionmentioning

confidence: 99%

Anisotropic $g$-tensors in hole quantum dots: The role of the transverse confinement direction

Qvist¹,

Danon²

2021

Preprint

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Qubits encoded in the spin state of heavy holes confined in Si-and Ge-based semiconductor quantum dots are currently leading the efforts toward spin-based quantum information processing. The virtual absence of spinful nuclei in purified samples yields long qubit coherence times and the intricate coupling between spin and momentum in the valence band can provide very fast spinorbit-based qubit control, e.g., via electrically induced modulations of the heavy-hole g-tensor. A thorough understanding of all aspects of the interplay between spin-orbit coupling, the confining potentials, and applied magnetic fields is thus quintessential for the development of the optimal hole-spin-based qubit platform. Here we theoretically investigate the manifestation of the effective g-tensor and effective mass of heavy holes in two-dimensional hole gases as well as in lateral quantum dots. We include the effects of the anisotropy of the effective Luttinger Hamiltonian (particularly relevant for Si-based systems) and we focus on the detailed role of the orientation of the transverse confining potential. We derive most general analytic expressions for the anisotropic g-tensor and we present a general and straightforward way to calculate corrections to this g-tensor for localized holes due to various types of spin-orbit interaction, exemplifying the approach by including a simple linear Rashba-like term. Our results thus contribute to the understanding needed to find optimal points in parameter space for hole-spin qubits, where confinement is effective and spin-orbit-mediated electric control over the spin states is efficient.

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Effective out-of-plane g-factor in strained-Ge/SiGe quantum dots

Cited by 3 publications

References 9 publications

Probing details of spin--orbit coupling through Pauli spin blockade

Probing details of spin--orbit coupling through Pauli spin blockade

Thermal activation of low-density Ga implanted in Ge

Anisotropic $g$-tensors in hole quantum dots: The role of the transverse confinement direction

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