Abstract
We demonstrate that superconducting gatemon qubits based on superconductor-semiconductor-superconductor Josephson junctions can be constructed on hole-type Ge/Si core/shell nanowires. The ...frequency of the qubit can be set firstly by controlling the diffusion of Al in the nanowire via thermal annealing, which yields a suitable critical supercurrent allowing the qubit frequency to be within the experimentally accessible range, and then by fine tuning of a gate voltage, by which an accurate adjustment of the frequency can be realized. On the resulted qubit, Rabi oscillation with an energy relaxation time
$${T}_{1} \sim 180\,{\rm{ns}}$$
T
1
~
180
ns
was observed in the time domain, an average decoherence time
$${T}_{2}^{* } \sim 15\,{\rm{ns}}$$
T
2
*
~
15
ns
was obtained, and the gate voltage dependence of both
$${T}_{1}$$
T
1
and
$${T}_{2}^{* }$$
T
2
*
was investigated. Such a hole-type superconducting gatemon qubit, based on materials with strong spin-orbit coupling and potentially the absence of hyperfine interaction after isotope purification, could be used for exploring the quantum coherence phenomena of hole-gas and even Majorana physics in Ge-based quantum devices.
Abstract
Coherence and tunneling play central roles in quantum phenomena. In a tunneling event, the time that a particle spends inside the barrier has been fiercely debated. This problem becomes more ...complex when tunneling repeatedly occurs back and forth, and when involving many particles. Here we report the measurement of the coherence time of various charge states tunneling in a nanowire-based tunable Josephson junction; including single charges, multiple charges, and Cooper pairs. We studied all the charge tunneling processes using Landau-Zener-Stückelberg-Majorana (LZSM) interferometry, and observed high-quality interference patterns under a microwave drive. In particular, the coherence time of the charge states tunneling back and forth was extracted from the interference fringes in Fourier space. In addition, our measurements show the break-up of Cooper pairs, from a macroscopic quantum coherent state to individual particle states. Besides the fundamental research interest, our results also establish LZSM interferometry as a powerful technique to explore the coherence time of charges in hybrid devices.
There have been continuous efforts in searching for unconventional superconductivity in the past five decades. Compared to the well-established d-wave superconductivity in cuprates, the existence of ...superconductivity with pairing symmetries of other high angular momentum is less conclusive. Bi/Ni epitaxial bilayer is a potential unconventional superconductor with broken time reversal symmetry (TRS), for that it demonstrates superconductivity and ferromagnetism simultaneously at low temperatures. We employ a specially designed superconducting quantum interference device (SQUID) to detect, on the Bi/Ni bilayer, the orbital magnetic moments which are expected if the TRS is broken. An anomalous hysteretic magnetic response is indeed observed in the superconducting state, providing the evidence for the existence of chiral superconducting domains in the material.
We report an experimental study of proximity induced superconductivity in planar Josephson junction devices made from free-standing InAs nanosheets. The nanosheets are grown by molecular beam ...epitaxy, and the Josephson junction devices are fabricated by directly contacting the nanosheets with superconductor Al electrodes. The fabricated devices are explored by low-temperature carrier transport measurements. The measurements show that the devices exhibit a gate-tunable supercurrent, multiple Andreev reflections, and a good quality superconductor-semiconductor interface. The superconducting characteristics of the Josephson junctions are investigated at different magnetic fields and temperatures and are analyzed based on the Bardeen–Cooper–Schrieffer (BCS) theory. The measurements of the ac Josephson effect are also conducted under microwave radiations with different radiation powers and frequencies, and integer Shapiro steps are observed. Our work demonstrates that InAs nanosheet based hybrid devices are desired systems for investigating the forefront of physics, such as two-dimensional topological superconductivity.
Many proposals for exploring topological quantum computation are based on superconducting quantum devices constructed on materials with strong spin–orbit coupling (SOC). For these devices, full ...control of both the magnitude and the spatial distribution of the supercurrent is highly demanded, but has been elusive up to now. We constructed a proximity-type Josephson junction on nanoplates of Bi2O2Se, a new emerging semiconductor with strong SOC. Through electrical gating, we show that the supercurrent can be fully turned ON and OFF, and its real-space pathways can be configured either through the bulk or along the edges. Our work demonstrates Bi2O2Se as a promising platform for constructing multifunctional hybrid superconducting devices as well as for searching for topological superconductivity.
Abstract Hybrid devices that combine superconductors (S) and semiconductors (Sm) have attracted great attention due to the integration of the properties of both materials, which relies on the ...interface details and the resulting coupling strength and wavefunction hybridization. However, until now, none of the experiments have reported good control of the band alignment of the interface, as well as its tunability to the coupling and hybridization. Here, the interface is modified by inducing specific argon milling while maintaining its high quality, e.g., atomic connection, which results in a large induced superconducting gap and ballistic transport. By comparing with Schrödinger–Poisson calculations, it is proven that this method can vary the band bending/coupling strength and the electronic spatial distribution. In the strong coupling regime, the coexistence and tunability of crossed Andreev reflection and elastic co‐tunneling—key ingredients for the Kitaev chain—are confirmed. This method is also generic for other materials and achieves a hard and huge superconducting gap in lead and indium antimonide nanowire (Pb‐InSb) devices. Such a versatile method, compatible with the standard fabrication process and accompanied by the well‐controlled modification of the interface, will definitely boost the creation of more sophisticated hybrid devices for exploring physics in solid‐state systems.
Many proposals for exploring topological quantum computation are based on superconducting quantum devices constructed on materials with strong spin-orbit coupling (SOC). For these devices, full ...control of both the magnitude and the spatial distribution of the supercurrent is highly demanded, but has been elusive up to now. We constructed a proximity-type Josephson junction on nanoplates of Bi
O
Se, a new emerging semiconductor with strong SOC. Through electrical gating, we show that the supercurrent can be fully turned ON and OFF, and its real-space pathways can be configured either through the bulk or along the edges. Our work demonstrates Bi
O
Se as a promising platform for constructing multifunctional hybrid superconducting devices as well as for searching for topological superconductivity.
Topological materials with boundary (surface/edge/hinge) states have attracted tremendous research interest. Additionally, unconventional (obstructed atomic) materials have recently drawn lots of ...attention owing to their obstructed boundary states. Experimentally, Josephson junctions (JJs) constructed on materials with boundary states produce the peculiar boundary supercurrent, which was utilized as a powerful diagnostic approach. Here, we report the observations of boundary supercurrent in NiTe
-based JJs. Particularly, applying an in-plane magnetic field along the Josephson current can rapidly suppress the bulk supercurrent and retain the nearly pure boundary supercurrent, namely the magnetic field filtering of supercurrent. Further systematic comparative analysis and theoretical calculations demonstrate the existence of unconventional nature and obstructed hinge states in NiTe
, which could produce hinge supercurrent that accounts for the observation. Our results reveal the probable hinge states in unconventional metal NiTe
, and demonstrate in-plane magnetic field as an efficient method to filter out the bulk contributions and thereby to highlight the hinge states hidden in topological/unconventional materials.
We carried out a phase-sensitive experiment on Josephson trijunctions constructed on the surface of three-dimensional topological insulator Bi2Te3. Through local flux contol and contact resistance ...measurement, we observed that the minigap at the ends of the trijunctions approaches zero linearly with varying phase difference and closes completely at π phase difference. The minigap at the center of the trijunction is protected to close over extended regions in phase space. These results agree with the theory by Fu and Kane Phys. Rev. Lett. 100, 096407 (2008).
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