Anisotropic 
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-tensors in hole quantum dots: Role of transverse confinement direction

Qvist, Jørgen Holme; Danon, Jeroen

doi:10.1103/physrevb.105.075303

Cited by 10 publications

(5 citation statements)

References 66 publications

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“…( 5) to find an exact analytical description of low-energy holes in a Ge or a Ge/Si core/shell NW. Our approach fully accounts for orbital magnetic field effects that are typically neglected or included perturbatively [76,77,86,87]. We find that, in Ge, these effects strongly renormalize the system response, and, thus, cannot be safely neglected even at weak magnetic fields.…”

Section: Analytical Solution For Ge Nanowiresmentioning

confidence: 99%

Enhanced orbital magnetic field effects in Ge hole nanowires

et al. 2022

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Hole semiconductor nanowires (NW) are promising platforms to host spin qubits and Majorana bound states for topological qubits because of their strong spin-orbit interactions (SOI). The properties of these systems depend strongly on the design of the cross section and on strain, as well as on external electric and magnetic fields. In this paper, we analyze in detail the dependence of the SOI and g factors on the orbital magnetic field. We focus on magnetic fields aligned along the axis of the NW, where orbital effects are enhanced and result in a renormalization of the effective g factor up to 400%, even at small values of magnetic field. We provide an exact analytical solution for holes in Ge NWs and we derive an effective low-energy model that enables us to investigate the effect of electric fields applied perpendicular to the NW. We also discuss in detail the role of strain, growth direction, and high-energy valence bands in different architectures, including Ge/Si core/shell NWs, gate-defined one-dimensional channels in planar Ge, and curved Ge quantum wells. By comparing NWs with different growth directions, we find that the isotropic approximation is well justified. Curved Ge quantum wells feature large effective g factors and SOI at low electric field, ideal for hosting Majorana bound states. In contrast, at strong electric field, these quantities are independent of the field, making hole spin qubits encoded in curved quantum wells to good approximation not susceptible to charge noise, and significantly boosting their coherence time.

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Section: Analytical Solution For Ge Nanowiresmentioning

confidence: 99%

Enhanced orbital magnetic field effects in Ge hole nanowires

et al. 2022

View full text Add to dashboard Cite

show abstract

“…( 5) to find an exact analytical description of lowenergy holes in a Ge or a Ge/Si core/shell NW. Our approach fully accounts for orbital magnetic field effects that are typically neglected or included perturbatively [76,77,86,87]. We find that, in Ge, these effects strongly renormalize the system response, and, thus, cannot be safely neglected even at weak magnetic fields.…”

Section: Analytical Solution For Ge Nanowiresmentioning

confidence: 99%

Enhanced orbital magnetic field effects in Ge hole nanowires

Adelsberger¹,

Bosco²,

Klinovaja³

et al. 2022

Preprint

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Hole semiconductor nanowires (NW) are promising platforms to host spin qubits and Majorana bound states for topological qubits because of their strong spin-orbit interactions (SOI). The properties of these systems depend strongly on the design of the cross section and on strain, as well as on external electric and magnetic fields. In this work, we analyze in detail the dependence of the SOI and g factors on the orbital magnetic field. We focus on magnetic fields aligned along the axis of the NW, where orbital effects are enhanced and result in a renormalization of the effective g factor up to 400 %, even at small values of magnetic field. We provide an exact analytical solution for holes in Ge NWs and we derive an effective low-energy model that enables us to investigate the effect of electric fields applied perpendicular to the NW. We also discuss in detail the role of strain, growth direction, and high energy valence bands in different architectures, including Ge/Si core/shell NWs, gate-defined one-dimensional channels in planar Ge, and curved Ge quantum wells. In core/shell NWs grown along the [110] direction the g factor can be twice larger than for other growth directions which makes this growth direction advantageous for Majorana bound states. Also curved Ge quantum wells feature large effective g factors and SOI, again ideal for hosting Majorana bound states. Strikingly, because these quantities are independent of the electric field, hole spin qubits encoded in curved quantum wells are to good approximation not susceptible to charge noise, significantly boosting their coherence time.

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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

Self Cite

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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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Anisotropic g -tensors in hole quantum dots: Role of transverse confinement direction

Cited by 10 publications

References 66 publications

Enhanced orbital magnetic field effects in Ge hole nanowires

Enhanced orbital magnetic field effects in Ge hole nanowires

Enhanced orbital magnetic field effects in Ge hole nanowires

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

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