Search results for: J. P. Kotthaus

Items from 1 to 16 out of 16 results

chapter

Nanomechanical resonators operating in the radio frequency regime as single charge detectors

R. H. Blick, A. Erbe, A. Tilke, H. Krömmer, more

Advances in Solid State Physics > Advances in Solid State Physics 39 > 121-130

We present our recent work on nanomachined electromechanical resonators applied as mechanically flexible beams and tunneling contacts operating in the radio frequency regime. We will discuss how to build Au/Si beams of lengths varying from 1–4 μm and width down to only 80 nm. The resonators are machined out of single-crystal silicon-on-insulator (SOI) substrates. We will demonstrate how these nanometersize...

chapter

A New Tool for Studying Phase Coherent Phenomena in Quantum Dots

R. H. Blick, A. W. Holleitner, H. Qin, F. Simmel, more

Lecture Notes in Physics > Statistical and Dynamical Aspects of Mesoscopic Systems > Quantum Dots > 35-44

Microwave transport spectroscopy on quantum dots with near-field microwave sources is presented. As microwave sources we employ two different Josephson oscillators, being integrated with the AlGaAs/GaAs-heterostructure in which the dots are formed. We observe photon assisted tunneling induced by the Josephson oscillators and compare the results with those using an externally operated microwave source.

chapter

Charged excitons in InAs quantum dots

R. J. Warburton, C. Bödefeld, C. S. Dürr, K. Karrai, more

Advances in Solid State Physics > Advances in Solid State Physics 38 > 183-192

We report studies of charged excitons in InAs quantum dots. The selfassembled dots are embedded in a field effect device so that the dots can be loaded with electrons by applying a bias between a metal gate and back contact. The dots are homogeneous enough for an ensemble of dots to show Coulomb blockade in the vertical transport. We have measured the optical activity of excitons by detecting minute...

chapter

Measuring nanomechanical motion with an imprecision below that at the standard quantum limit

G. Anetsberger, P. Verlot, E. Gavartin, O. Arcizet, more

2011 Conference on Lasers and Electro-Optics Europe and 12th European Quantum Electronics Conference (CLEO EUROPE/EQEC) > 1

2011 Conference on Lasers & Electro-Optics Europe & 12th European Quantum Electronics Conference CLEO EUROPE/EQEC

In the past decade, impressive efforts have been powered in the field of optomechanics that is the study of the coupling between a light field and a mechanical degree of freedom, with the major aims of detecting the quantum zero-point motion fluctuations of a mechanical object, and studying the fundamental quantum measurement processes. Though having their own specificities, both aims require combining...

chapter

Measuring nanomechanical motion with an imprecision below that at the standard quantum limit

G. Anetsberger, P. Verlot, E. Gavartin, O. Arcizet, more

CLEO: 2011 - Laser Science to Photonic Applications > 1 - 2

2011 Conference on Lasers and Electro-Optics (CLEO)

We report an optomechanical near-field coupling detection scheme which enabled the first optical measurement of nanomechanical motion with an imprecision 3 dB below that at the standard quantum limit at room temperature.

chapter

Near-field cavity optomechanics with nanomechanical oscillators

G Anetsberger, O Arcizet, E Gavartin, Q P Unterreithmeier, more

CLEO/QELS: 2010 Laser Science to Photonic Applications > 1 - 2

2010 Conference on Lasers and Electro-Optics (CLEO)

We use evanescent near-fields of high-Q optical microresonators to extend cavity-optomechanical coupling to nanomechanical oscillators. Pure radiation pressure coupling to SiN nanomechanical strings is demonstrated. Dynamical backaction allows creating laser-like nanomechanical oscillation at nanowatt threshold.

chapter

Optical measurement of nanomechanical motion with an imprecision at the standard quantum limit

G Anetsberger, O Arcizet, E Gavartin, Q P Unterreithmeier, more

CLEO/QELS: 2010 Laser Science to Photonic Applications > 1 - 2

2010 Conference on Lasers and Electro-Optics (CLEO)

Ultra-high Q optical microresonators allow measuring nanomechanical motion with unprecedented sensitivity. For the first time, we reach a measurement imprecision at the standard quantum limit which has been a long sought-after goal for nanomechanical oscillators.

article

Ballistic magnetotransport in a semiconductor microjunction with broken symmetry

A. M. Song, A. Lorke, J. P. Kotthaus, W. Wegscheider, more

Superlattices and Microstructures > 1999 > 25 > 1-2 > 149-152

The linear and nonlinear magnetotransport response of a ballistic semiconductor cross junction with an embedded, symmetry-breaking scatterer is investigated. As a result of the broken symmetry, the so-called 'bend resistance' is no longer symmetric in the magnetic field. The experimental curve also exhibits a pronounced peak structure. In the nonlinear transport regime, both the magnitude and the...

article

A nonlinear transport device with no intrinsic threshold

A. M. Song, S. Manus, M. Streibl, A. Lorke, more

Superlattices and Microstructures > 1999 > 25 > 1-2 > 269-272

A ballistic rectifier, based on guidance of carriers by a triangular antidot, is shown to be both experimentally and theoretically capable of operating for weak signals. At T=4.2 K, we find that the ballistic rectifier works when the input voltage is as low as 0.5 mV, the same order ofk _B T. Based on an extended Landauer-Buttiker formula for nonlinear transport, we show that even when the...

article

Nanolithography with an atomic force microscope

M. Wendel, B. Irmer, J. Cortes, R. Kaiser, more

Superlattices and Microstructures > 1996 > 20 > 3 > 349-356

A lithographic technique, employing the vibrating tip of an atomic force microscope to mechanically pattern various materials such as photoresist, metals or semiconductors in the nanometre regime has been developed. We use this technique for the fabrication of etch masks as well as for the patterning of evaporation shadow masks.The tip quality has been found to be a crucial factor in the lithographic...

article

Collective effects in the intersubband resonance of InAs/AlSb quantum wells

R. J. Warburton, C. Gauer, A. Wixforth, J. P. Kotthaus, more

Superlattices and Microstructures > 1996 > 19 > 4 > 365-374

The consequences of a highly nonparabolic band structure on intersubband resonance are explored with experiments and theory on InAs/AlSb quantum wells. From a single-particle viewpoint, the intersubband resonance is expected to be broad because the intersubband spacing is highlyk-dependent. Experimentally, however, we observe a relatively narrow line and this is interpreted as evidence that the intersubband...

article

Spin phenomena in intersubband transitions

C. Gauer, A. Wixforth, J. P. Kotthaus, B. Brar, more

Superlattices and Microstructures > 1996 > 19 > 3 > 241-249

Intersubband transitions have been studied in InAs/AlSb multi quantum wells subjected to a parallel magnetic field. In this Voigt configuration we observe two resonances whose oscillator strengths increase with magnetic field. The high energy line is interpreted as a superposition of two spin-conserving intersubband transitions while the low energy resonance corresponds to two combined spin-flip intersubband...

article

Photon-assisted tunneling in coupled double quantum wells

G. Blanke, A. Lorke, J. P. Kotthaus, J. H. English, more

Solid State Electronics > 1996 > 40 > 1-8 > 421-424

Using different techniques to individually contact two closely spaced electron gases, we study the tunneling characteristics between weakly coupled GaAs quantum wells, with and without resonant far-infrared excitation. We find that for barriers as thick as 300 , the alignment between the subbands in the wells can be observed as an increased tunneling conductivity. To study photon-assisted tunneling...

article

Magneto transport on antidot arrays, fabricated by an atomic force microscope

M. Wendel, H. Lorenz, J. P. Kotthaus, M. Holland

Solid State Electronics > 1996 > 40 > 1-8 > 25-28

A recently introduced lithographic tool employing an atomic force microscope is improved and utilized to fabricate nanometer-scale antidot arrays. The AFM periodically creates holes in a thin photoresist, covering a conventional mesa-etched GaAs-AlGaAs heterostructure. To minimize the period of produced holes in the resist we now use carbon AFM supertips, prepared in a scanning electron microscope...

article

Cyclotron resonance of electron-hole systems in InAs/GaSb/AlSb

R. J. Warburton, B. Brar, C. Gauer, A. Wixforth, more

Solid State Electronics > 1996 > 40 > 1-8 > 679-682

We present cyclotron resonance measurements on electron-hole systems in the crossed gap system InAs/GaSb with additional confinement from AlSb barriers. A large, 2.5 meV, splitting has been observed in the electron cyclotron resonance when holes are also present. We focus on the pronounced filling factor dependence of the effect to argue that we have a nonparabolicity-induced splitting, enhanced...

article

Quantized conductance in a Si/Si ₀ _. ₇ Ge ₀ _. ₃ split-gate device and impurity-related magnetotransport phenomena

D. Többen, D. A. Wharam, G. Abstreiter, J. P. Kotthaus, more

Solid State Electronics > 1996 > 40 > 1-8 > 405-408

We have defined a quantum point-contact by the split-gate technique in a Si/SiGe heterostructure containing a two-dimensional electron gas with an elastic mean free path of about 1.3 μm. The conductance of this device shows typical steps very close to multiples of 4e ² h ^- ¹ . Upon application of a perpendicular magnetic field the spin and valley degeneracies are lifted and magnetic...

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