suspended CVD graphene
Our groups has been pioneering shot-noise measurements in nanodevices.1 We have studied noise in various geometries, in the single-electron tunneling device,2 in diffusive wires,3,4 in metallic S-N devices,5 in ballistic cavities6 and in quantum Hall devices where we could demonstrate the antibunching of fermions.7,8 These studies were all done at modest detection frequencies in the 10-100kHz range. In recent years, we have developed a noise measurements scheme that works in the GHz window where we can benefit from low-noise cryogenic HEMT amplifiers.9 Due to the 50W transmission lines, we had to develop impedance matching circuits to efficiently interface high impedance quantum devices,10 such as QDs. We are currently studying shot-noise in clean QDs where we can resolve a detailed map of Fano factors in different gate- and bias voltage regions where different processes involving the QD ground and excited states are relevant.
- C. Beenakker and CS, Phys. Today 56 (5), 37-42 (2003).
- H. Birk, M. J. M. Dejong and CS, Phys. Rev. Lett. 75 (8), 1610-1613 (1995).
- M. Henny, H. Birk, R. Huber, C. Strunk, A. Bachtold, M. Kruger and CS, Appl. Phys. Lett. 71 (6), 773-775 (1997).
- M. Henny, S. Oberholzer, C. Strunk and CS, Phys. Rev. B 59 (4), 2871-2880 (1999).
- T. Hoss, C. Strunk, T. Nussbaumer, R. Huber, U. Staufer and CS, Phys. Rev. B 62 (6), 4079-4085 (2000).
- S. Oberholzer, E. V. Sukhorukov and CS, Nature 415 (6873), 765-767 (2002).
- M. Henny, S. Oberholzer, C. Strunk, T. Heinzel, K. Ensslin, M. Holland and CS, Science 284 (5412), 296 (1999).
- S. Oberholzer, M. Henny, C. Strunk, C. Schonenberger, T. Heinzel, K. Ensslin and M. Holland, Physica E 6 (1-4), 314-317 (2000).
- T. Hasler, M. Jung, V. Ranjan, G. Puebla-Hellmann, A. Wallraff and CS, Phys. Rev. Appl. 4 (5), 054002 (2015).
Funding: ERC-QUEST, SNF, NCCR-QSIT
Relevant papers (keyword: NOISE):
- Blocking-state influence on shot noise and conductance in quantum dots
M. -C. Harabula, V. Ranjan, R. Haller, G. Fülöp, and C. Schönenberger.
Phys. Rev. B, 97:115403, mar 2018. arXiv:1801.00286
Quantum dots (QDs) investigated through electron transport measurements often exhibit varying, state-dependent tunnel couplings to the leads. Under specic conditions, weakly coupled states can result in a strong suppression of the electrical current and they are correspondingly called blocking states. Using the combination of conductance and shot noise measurements, we investigate blocking states in carbon nanotube (CNT) QDs. We report negative dierential conductance and super- Poissonian noise. The enhanced noise is the signature of electron bunching, which originates from random switches between the strongly and weakly conducting states of the QD. Negative differential conductance appears here when the blocking state is an excited state. In this case, at the threshold voltage where the blocking state becomes populated, the current is reduced. Using a master equation approach, we provide numerical simulations reproducing both the conductance and the shot noise pattern observed in our measurements.
- Measuring a Quantum Dot with an Impedance-Matching On-Chip Superconducting LC Resonator at Gigahertz Frequencies
M. -C. Harabula, T. Hasler, G. Fülöp, M. Jung, V. Ranjan, and C. Schönenberger.
Phys. Rev. Appl., 8:54006, nov 2017. arXiv:1707.09061
We report on the realization of a bonded-bridge on-chip superconducting coil and its use in impedance matching a highly ohmic quantum dot (QD) to a 3-GHz measurement setup. The coil, modeled as a lumped-element LC resonator, is more compact and has a wider bandwidth than resonators based on coplanar transmission lines (e.g., λ/4 impedance transformers and stub tuners), at potentially better signal-to-noise ratios. Specifically, for measurements of radiation emitted by the device, such as shot noise, the 50 × larger bandwidth reduces the time to acquire the spectral density. The resonance frequency, close to 3.25 GHz, is 3 times higher than that of the one previously reported, a wire-bonded coil. As a proof of principle, we fabricate an LC circuit that achieves impedance matching to an approximately 15 kOhm load and validate it with a load defined by a carbon nanotube QD, whose shot noise we measure in the Coulomb-blockade regime.
- Shot Noise of a Quantum Dot Measured with Gigahertz Impedance Matching
T. Hasler, M. Jung, V. Ranjan, G. Puebla-Hellmann, A. Wallraff, and C. Schönenberger.
Physical Review Applied, 4(5):54002, Nov 2015. arXiv:1507.04884.pdf
The demand for a fast high-frequency read-out of high-impedance devices, such as quantum dots, necessitates impedance matching. Here we use a resonant impedance-matching circuit (a stub tuner) realized by on-chip superconducting transmission lines to measure the electronic shot noise of a carbonnanotube quantum dot at a frequency close to 3 GHz in an efficient way. As compared to wideband detection without impedance matching, the signal-to-noise ratio can be enhanced by as much as a factor of 800 for a device with an impedance of 100 kOmega. The advantage of the stub resonator concept is the ease with which the response of the circuit can be predicted, designed, and fabricated. We further demonstrate that all relevant matching circuit parameters can reliably be deduced from power-reflectance measurements and then used to predict the power-transmission function from the device through the circuit. The shot noise of the carbon-nanotube quantum dot in the Coulomb blockade regime shows an oscillating suppression below the Schottky value of 2eI, as well as an enhancement in specific regions
- Quantum Shot Noise
C. Beenakker and C. Schönenberger.
Physics Today, 56(5):37-42, May 2003.
- From Photon Bunching to Electron Antibunching
Bulletin of the SSOM, 2003.
- Shot noise of series quantum point contacts intercalating chaotic cavities
S. \. Oberholzer, E. \. V. \. Sukhorukov, C. \. Strunk, and C. \. Schönenberger.
Phys. Rev. B, 66:233304, 2002.
- Crossover between classical and quantum shot noise in chaotic cavities�
S. \. Oberholzer, E. V. \. Sukhorukov, and C. \. Schönenberger.
Nature, 415:765, 2002.
- Shot Noise by Quantum Scattering in Chaotic Cavities
S.~Oberholzer, E.~V.~Sukhorukov, C.~Strunk, C.~Schönenberger, T.~Heinzel, and M.~Holland.
Phys. Rev. Lett., 86(10):2114-2117, 2001.
- Shot Noise in Schottky’s Vacuum Tube is Classical
C. \. Schönenberger, S. Oberholzer, E. V. Sukhorukov, and H. Grabert.
cond-mat/0112504, pages 1-5, 2001.
- The Hanbury Brown and Twiss Experiment with Fermions
S. Oberholzer, M. Henny, C. Strunk, C. Schönenberger, T. Heinzel, K. Ensslin, and M. Holland.
Physica E, 6:314-317, 2000.
- The 1/3-shot noise suppression in diffusive nanowires
M. Henny, S. Oberholzer, C. Strunk, and C. Schönenberger.
Phys.\ Rev.\ B., 59:2871, 1999.
- The Fermionic Hanbury-Brown & Twiss Experiment
M. Henny, S. Oberholzer, C. Strunk, T. Heinzel, K. Ensslin, M. Holland, and C. Schönenberger.
Science, 284:296, 1999.
- Electron Heating Effects in Diffusive Metal Wires
M. Henny, H. Birk, R. Huber, C. Strunk, A. Bachtold, M. Krüger, and C. Schönenberger.
Appl. Phys. Lett., 71:773, 1997.
- Preamplifier for Electrical Current Noise Measurements at Low Temperatures
H. Birk, K. Oostveen, and C. Schönenberger.
Rev. Sci. Instr., 67:2977, 1996.
- Shot-noise suppression in the single-electron tunneling regime
H. Birk, M. J. M. de Jong, and C. Schönenberger.
Phys. Rev. Lett., 75:1610, 1995.