| 1. |
- Deng, Mingtang, et al.
(författare)
-
Parity independence of the zero-bias conductance peak in a nanowire based topological superconductor-quantum dot hybrid device.
- 2014
-
Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 4
-
Tidskriftsartikel (refereegranskat)abstract
- We explore the signatures of Majorana fermions in a nanowire based topological superconductor-quantum dot-topological superconductor hybrid device by charge transport measurements. At zero magnetic field, well-defined Coulomb diamonds and the Kondo effect are observed. Under the application of a finite, sufficiently strong magnetic field, a zero-bias conductance peak structure is observed. It is found that the zero-bias conductance peak is present in many consecutive Coulomb diamonds, irrespective of the even-odd parity of the quasi-particle occupation number in the quantum dot. In addition, we find that the zero-bias conductance peak is in most cases accompanied by two differential conductance peaks, forming a triple-peak structure, and the separation between the two side peaks in bias voltage shows oscillations closely correlated to the background Coulomb conductance oscillations of the device. The observed zero-bias conductance peak and the associated triple-peak structure are in line with Majorana fermion physics in such a hybrid topological system.
|
|
| 2. |
|
|
| 3. |
- Fan, Dingxun, et al.
(författare)
-
Formation of long single quantum dots in high quality InSb nanowires grown by molecular beam epitaxy
- 2015
-
Ingår i: Nanoscale. - : Royal Society of Chemistry (RSC). - 2040-3372 .- 2040-3364. ; 7:36, s. 14822-14828
-
Tidskriftsartikel (refereegranskat)abstract
- We report on realization and transport spectroscopy study of single quantum dots (QDs) made from InSb nanowires grown by molecular beam epitaxy (MBE). The nanowires employed are 50-80 nm in diameter and the QDs are defined in the nanowires between the source and drain contacts on a Si/SiO2 substrate. We show that highly tunable QD devices can be realized with the MBE-grown InSb nanowires and the gate-to-dot capacitance extracted in the many-electron regimes is scaled linearly with the longitudinal dot size, demonstrating that the devices are of single InSb nanowire QDs even with a longitudinal size of similar to 700 nm. In the few-electron regime, the quantum levels in the QDs are resolved and the Lande g-factors extracted for the quantum levels from the magnetotransport measurements are found to be strongly level-dependent and fluctuated in a range of 18-48. A spin-orbit coupling strength is extracted from the magnetic field evolutions of a ground state and its neighboring excited state in an InSb nanowire QD and is on the order of similar to 300 mu eV. Our results establish that the MBE-grown InSb nanowires are of high crystal quality and are promising for the use in constructing novel quantum devices, such as entangled spin qubits, one-dimensional Wigner crystals and topological quantum computing devices.
|
|
| 4. |
- Fang, Li Tai, et al.
(författare)
-
Establishing community reference samples, data and call sets for benchmarking cancer mutation detection using whole-genome sequencing
- 2021
-
Ingår i: Nature Biotechnology. - : Springer Nature. - 1087-0156 .- 1546-1696. ; 39:9, s. 1151-1160
-
Tidskriftsartikel (refereegranskat)abstract
- Tumor-normal paired DNA samples from a breast cancer cell line and a matched lymphoblastoid cell line enable calibration of clinical sequencing pipelines and benchmarking 'tumor-only' or 'matched tumor-normal' analyses. The lack of samples for generating standardized DNA datasets for setting up a sequencing pipeline or benchmarking the performance of different algorithms limits the implementation and uptake of cancer genomics. Here, we describe reference call sets obtained from paired tumor-normal genomic DNA (gDNA) samples derived from a breast cancer cell line-which is highly heterogeneous, with an aneuploid genome, and enriched in somatic alterations-and a matched lymphoblastoid cell line. We partially validated both somatic mutations and germline variants in these call sets via whole-exome sequencing (WES) with different sequencing platforms and targeted sequencing with >2,000-fold coverage, spanning 82% of genomic regions with high confidence. Although the gDNA reference samples are not representative of primary cancer cells from a clinical sample, when setting up a sequencing pipeline, they not only minimize potential biases from technologies, assays and informatics but also provide a unique resource for benchmarking 'tumor-only' or 'matched tumor-normal' analyses.
|
|
| 5. |
- Xiao, Wenming, et al.
(författare)
-
Toward best practice in cancer mutation detection with whole-genome and whole-exome sequencing
- 2021
-
Ingår i: Nature Biotechnology. - : Springer Nature. - 1087-0156 .- 1546-1696. ; 39:9, s. 1141-1150
-
Tidskriftsartikel (refereegranskat)abstract
- Recommendations are given on optimal read coverage and selection of calling algorithm to maximize the reproducibility of cancer mutation detection in whole-genome or whole-exome sequencing. Clinical applications of precision oncology require accurate tests that can distinguish true cancer-specific mutations from errors introduced at each step of next-generation sequencing (NGS). To date, no bulk sequencing study has addressed the effects of cross-site reproducibility, nor the biological, technical and computational factors that influence variant identification. Here we report a systematic interrogation of somatic mutations in paired tumor-normal cell lines to identify factors affecting detection reproducibility and accuracy at six different centers. Using whole-genome sequencing (WGS) and whole-exome sequencing (WES), we evaluated the reproducibility of different sample types with varying input amount and tumor purity, and multiple library construction protocols, followed by processing with nine bioinformatics pipelines. We found that read coverage and callers affected both WGS and WES reproducibility, but WES performance was influenced by insert fragment size, genomic copy content and the global imbalance score (GIV; G > T/C > A). Finally, taking into account library preparation protocol, tumor content, read coverage and bioinformatics processes concomitantly, we recommend actionable practices to improve the reproducibility and accuracy of NGS experiments for cancer mutation detection.
|
|
| 6. |
|
|
| 7. |
- Yu, Chunlin
(författare)
-
Quantum Transport in Superconductor-Semiconductor Nanowire Hybrid Devices
- 2018
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In this thesis, we study quantum transport properties of superconductor-semiconductor nanowire hybrid devices. We mainly focus on the quantum transport in InSb nanowire Josephson quantum dot devices, i.e. quantum dots coupled to two pieces of superconductors. In such a structure, many-body interacting phenomena occur, such as Kondo correlation, multiple Andreev reflection, and the formation of Andreev bound states (ABSs) and Majorana bound states (MBSs).InSb nanowire is an ideal candidate for electronic and spintronic applications. Among all of the binary III-V semiconductors, InSb (bulk) has the narrowest band gap (Eg∼0.17 eV), the highest electron mobility (μe∼77,000 cm2V-1s-1), the smallest effective electron mass (m*∼0.014 me), the largest electron g*-factor (g*∼51), and the largest spin-orbit interaction (α up to 100 meV·nm). InSb nanowire is therefore predicted to be a promising harbouring system for MBSs --- a key ingredient for topological quantum computing --- when it is coupled to a s-wave superconductor. When an InSb nanowire is coupled to two s-wave superconductor leads (Al or Nb in this thesis), a quantum dot is naturally formed in the nanowire segment between the superconductors. Such a device can be configured to various regimes upon applying different strength of external electrical field and magnetic field. In particular, with a Zeeman field perpendicularly applied to the spin-orbit field direction, the device is predicted to host two pairs of MBSs mediated by the inter-quantum-dot, which will give rise to a zero-bias conductance peak (ZBCP) in the tunnelling spectrum as a signature of MBSs.However, except MBSs, other trivial mechanism can also cause emergent ZBCPs in a magnetic field, e.g. recovered Kondo resonances by a magnetic field, ABSs at quantum phase transition, etc. We hence take the emergent ZBCPs in magnetic field, both trivial and nontrivial, as the main thread of this thesis. We explore their physical origins and related physics with the main focuses on transport features in the Kondo-superconductor competing regime, lead state detection via a p-type quantum dot, anomalous negative magnetoresistance with Kondo correlations, and parity-independent ZBCPs. These measurements and discussion aim to be one step closer of the understandings of how a single magnetic impurity interacts with a superconductor, how to distinguish topologically trivial/non-trivial physics, and unveil more novel physics in the Josephson quantum dot structures.
|
|
