| 1. |
|
|
| 2. |
- Purcell, Shaun M., et al.
(författare)
-
Common polygenic variation contributes to risk of schizophrenia and bipolar disorder
- 2009
-
Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 460:7256, s. 748-752
-
Tidskriftsartikel (refereegranskat)abstract
- Schizophrenia is a severe mental disorder with a lifetime risk of about 1%, characterized by hallucinations, delusions and cognitive deficits, with heritability estimated at up to 80%(1,2). We performed a genome-wide association study of 3,322 European individuals with schizophrenia and 3,587 controls. Here we show, using two analytic approaches, the extent to which common genetic variation underlies the risk of schizophrenia. First, we implicate the major histocompatibility complex. Second, we provide molecular genetic evidence for a substantial polygenic component to the risk of schizophrenia involving thousands of common alleles of very small effect. We show that this component also contributes to the risk of bipolar disorder, but not to several non-psychiatric diseases.
|
|
| 3. |
- Barker, David, et al.
(författare)
-
Experimental Verification of the Work Fluctuation-Dissipation Relation for Information-to-Work Conversion
- 2022
-
Ingår i: Physical Review Letters. - 0031-9007. ; 128:4
-
Tidskriftsartikel (refereegranskat)abstract
- We study experimentally work fluctuations in a Szilard engine that extracts work from information encoded as the occupancy of an electron level in a semiconductor quantum dot. We show that as the average work extracted per bit of information increases toward the Landauer limit Formula Presented, the work fluctuations decrease in accordance with the work fluctuation-dissipation relation. We compare the results to a protocol without measurement and feedback and show that when no information is used, the work output and fluctuations vanish simultaneously, contrasting the information-to-energy conversion case where increasing amount of work is produced with decreasing fluctuations. Our study highlights the importance of fluctuations in the design of information-to-work conversion processes.
|
|
| 4. |
- Barker, D., et al.
(författare)
-
Individually addressable double quantum dots formed with nanowire polytypes and identified by epitaxial markers
- 2019
-
Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 114:18
-
Tidskriftsartikel (refereegranskat)abstract
- Double quantum dots (DQDs) hold great promise as building blocks for quantum technology as they allow for two electronic states to coherently couple. Defining QDs with materials rather than using electrostatic gating allows for QDs with a hard-wall confinement potential and more robust charge and spin states. An unresolved problem is how to individually address these QDs, which is necessary for controlling quantum states. We here report the fabrication of DQD devices defined by the conduction band edge offset at the interface of the wurtzite and zinc blende crystal phases of InAs in nanowires. By using sacrificial epitaxial GaSb markers selectively forming on one crystal phase, we are able to precisely align gate electrodes allowing us to probe and control each QD independently. We hence observe textbooklike charge stability diagrams, a discrete energy spectrum, and electron numbers consistent with theoretical estimates and investigate the tunability of the devices, finding that changing the electron number can be used to tune the tunnel barrier as expected by simple band diagram arguments.
|
|
| 5. |
- Chou, Y. -C., et al.
(författare)
-
Atomic-Scale Variability and Control of III-V Nanowire Growth Kinetics
- 2014
-
Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 1095-9203 .- 0036-8075. ; 343:6168, s. 281-284
-
Tidskriftsartikel (refereegranskat)abstract
- In the growth of nanoscale device structures, the ultimate goal is atomic-level precision. By growing III-V nanowires in a transmission electron microscope, we measured the local kinetics in situ as each atomic plane was added at the catalyst-nanowire growth interface by the vapor-liquid-solid process. During growth of gallium phosphide nanowires at typical V/III ratios, we found surprising fluctuations in growth rate, even under steady growth conditions. We correlated these fluctuations with the formation of twin defects in the nanowire, and found that these variations can be suppressed by switching to growth conditions with a low V/III ratio. We derive a growth model showing that this unexpected variation in local growth kinetics reflects the very different supply pathways of the V and III species. The model explains under which conditions the growth rate can be controlled precisely at the atomic level.
|
|
| 6. |
- Dalelkhan, B., et al.
(författare)
-
Ambipolar transport in narrow bandgap semiconductor InSb nanowires
- 2020
-
Ingår i: Nanoscale. - : Royal Society of Chemistry (RSC). - 2040-3364 .- 2040-3372. ; 12:15, s. 8159-8165
-
Tidskriftsartikel (refereegranskat)abstract
- We report on a transport measurement study of top-gated field effect transistors made out of InSb nanowires grown by chemical vapor deposition. The transistors exhibit ambipolar transport characteristics revealed by three distinguished gate-voltage regions: In the middle region where the Fermi level resides within the bandgap, the electrical resistance shows an exponential dependence on temperature and gate voltage. With either more positive or negative gate voltages, the devices enter the electron and hole transport regimes, revealed by the resistance decreasing linearly with decreasing temperature. From the transport measurement data of a 1 μm-long device made from a nanowire of 50 nm in diameter, we extracted a bandgap energy of 190-220 meV. The off-state current of this device is found to be suppressed within the measurement noise at a temperature of T = 4 K. A shorter, 260 nm-long device is found to exhibit a finite off-state current and a circumference-normalized on-state hole current of 11 μA μm-1 at VD = 50 mV which is the highest for such a device to our knowledge. The ambipolar transport characteristics make the InSb nanowires attractive for CMOS electronics, hybrid electron-hole quantum systems and hole based spin qubits.
|
|
| 7. |
|
|
| 8. |
|
|
| 9. |
- Haldar, Subhomoy, et al.
(författare)
-
Energetics of Microwaves Probed by Double Quantum Dot Absorption
- 2023
-
Ingår i: Physical Review Letters. - 0031-9007. ; 130:8
-
Tidskriftsartikel (refereegranskat)abstract
- We explore the energetics of microwaves interacting with a double quantum dot photodiode and show wave-particle aspects in photon-assisted tunneling. The experiments show that the single-photon energy sets the relevant absorption energy in a weak-drive limit, which contrasts the strong-drive limit where the wave amplitude determines the relevant-energy scale and opens up microwave-induced bias triangles. The threshold condition between these two regimes is set by the fine-structure constant of the system. The energetics are determined here with the detuning conditions of the double dot system and stopping-potential measurements that constitute a microwave version of the photoelectric effect.
|
|
| 10. |
- Havir, Harald, et al.
(författare)
-
Quantum dot source-drain transport response at microwave frequencies
- 2023
-
Ingår i: Physical Review B. - 2469-9950. ; 108:20
-
Tidskriftsartikel (refereegranskat)abstract
- Quantum dots are frequently used as charge-sensitive devices in low-temperature experiments to probe electric charge in mesoscopic conductors where the current running through the quantum dot is modulated by the nearby charge environment. Recent experiments have operated these detectors using reflectometry measurements up to gigahertz frequencies rather than probing the low-frequency current through the dot. In this work, we use an on-chip coplanar waveguide resonator to measure the source-drain transport response of two quantum dots at a frequency of 6 GHz, further increasing the bandwidth limit for charge detection. Similar to that in the low-frequency domain, the response is here predominantly dissipative. For large tunnel coupling, the response is still governed by the low-frequency conductance, in line with Landauer-Büttiker theory. For smaller couplings, our devices showcase two regimes where the high-frequency response deviates from the low-frequency limit and Landauer-Büttiker theory: When the photon energy exceeds the quantum dot resonance linewidth, degeneracy-dependent plateaus emerge. These are reproduced by sequential tunneling calculations. In the other case with large asymmetry in the tunnel couplings, the high-frequency response is two orders of magnitude larger than the low-frequency conductance G, favoring the high-frequency readout.
|
|
