Laboratory for Emerging Nanometrology Braunschweig

Braunschweig, Germany

Laboratory for Emerging Nanometrology Braunschweig

Braunschweig, Germany
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Silvestrov P.G.,TU Braunschweig | Recher P.,TU Braunschweig | Recher P.,Laboratory for Emerging Nanometrology Braunschweig
Physical Review B - Condensed Matter and Materials Physics | Year: 2017

It is generally believed that a Wigner crystal in single layer graphene cannot form because the magnitudes of the Coulomb interaction and the kinetic energy scale similarly with decreasing electron density. However, this scaling argument does not hold for the low energy states in bilayer graphene. We consider the formation of a Wigner crystal in weakly doped bilayer graphene with an energy gap opened by a perpendicular electric field. We argue that in this system the formation of the Wigner crystal is not only possible, but different phases of the crystal with very peculiar properties may exist here depending on the system parameters. © 2017 American Physical Society.


Recher P.,TU Braunschweig | Recher P.,Laboratory for Emerging Nanometrology Braunschweig
Technisches Messen | Year: 2017

In this short review article we will discuss the implications of quantum physics on measurement uncertainties that will be illustrated by concrete examples from quantum metrology. The article starts with a discussion on the differences in possible measurement outcomes between classical physics and quantum physics. Then we will present examples from quantum transport which define the so calledmetrological triangle-quantum Hall effect, Josephson effect and quantized charge pumping. Non-classical quantummechanical properties such as entanglement or squeezed lightwill be explained and their positive consequences on measurement uncertainties will be given. The article closes with a conclusion, where also new directions for quantized transport properties will be highlighted.


Wasisto H.S.,TU Braunschweig | Wasisto H.S.,Laboratory for Emerging Nanometrology Braunschweig | Merzsch S.,TU Braunschweig | Steib F.,TU Braunschweig | And 5 more authors.
Micro and Nano Letters | Year: 2014

The fabrication and use of silicon nanowire (SiNW) array-patterned microcantilever sensors for enhancing aerosol mass detection are described. Surface modification of the cantilever is performed selectively by combining the processes of nanoimprint lithography, photolithography and inductively coupled plasma cryogenic reactive ion etching. Cylindrical wire structures of 300 nm diameter with aspect ratios of 3-7 can be realised for the current SiNWs, which can be altered depending on the nanoimprint stamp size and etching recipe. Owing to the rise in the collection surface area of the sensor provided by vertical SiNWs, an increase of aerosol sampling efficiency can be obtained during cigarette smoke exposure, which is a factor of 1.5 higher than that of a corresponding plain cantilever. This proposed structure is intended to be used as a sensor module of a personal aerosol mass detector. © The Institution of Engineering and Technology 2014.


Silvestrov P.G.,TU Braunschweig | Recher P.,TU Braunschweig | Recher P.,Laboratory for Emerging Nanometrology Braunschweig | Brouwer P.W.,Free University of Berlin
Physical Review B - Condensed Matter and Materials Physics | Year: 2016

The current through a helical edge state of a quantum spin Hall insulator may be fully transmitted through a magnetically gapped region due to a combination of spin-transfer torque and spin pumping [Meng, Phys. Rev. B 90, 205403 (2014)PRBMDO1098-012110.1103/PhysRevB.90.205403]. Using a scattering approach, we here argue that in such a system the current is effectively carried by electrons with energies below the magnet-induced gap and well below the Fermi energy. This has striking consequences, such as the absence of shot noise, an exponential suppression of thermal noise, and an obstruction of thermal transport. For two helical edges covered by the same quantum magnet, the device can act as a robust noiseless current splitter. © 2016 American Physical Society.


Probst B.,TU Braunschweig | Virtanen P.,Aalto University | Recher P.,TU Braunschweig | Recher P.,Laboratory for Emerging Nanometrology Braunschweig
Physical Review B - Condensed Matter and Materials Physics | Year: 2015

We investigate a Zeeman-split quantum dot (QD) containing a single spin 1/2 weakly coupled to a helical Luttinger liquid (HLL) within a generalized master equation approach. The HLL induces a tunable magnetization direction on the QD controlled by an applied bias voltage when the quantization axes of the QD and the HLL are noncollinear. The backscattering conductance (BSC) in the HLL is finite and shows a resonance feature when the bias voltage equals the Zeeman energy in magnitude. The observed BSC asymmetry in bias voltage directly reflects the quantization axis of the HLL spin. © 2015 American Physical Society. ©2015 American Physical Society.


Strom A.,TU Braunschweig | Johannesson H.,Gothenburg University | Recher P.,TU Braunschweig | Recher P.,Laboratory for Emerging Nanometrology Braunschweig
Physical Review B - Condensed Matter and Materials Physics | Year: 2015

We study the entanglement production in a quantum spin Hall ring geometry where electrons of opposite spins are emitted in pairs from a source and collected in two different detectors. Postselection of coincidence detector events gives rise to entanglement in the system, measurable through correlations between the outcomes in the detectors. We have chosen a geometry such that the entanglement depends on the dynamical phases picked up by the edge states as they move around the ring. In turn, the dependence of the phases on gate potential and Rashba interaction allows for a precise electrical control of the entanglement production in the ring. © 2015 American Physical Society.


Schroer A.,TU Braunschweig | Recher P.,TU Braunschweig | Recher P.,Laboratory for Emerging Nanometrology Braunschweig
Physical Review B - Condensed Matter and Materials Physics | Year: 2015

We model a superconducting p-n junction in which the n and the p sides are contacted through two optical quantum dots (QDs), each embedded into a photonic nanocavity. Whenever a Cooper pair is transferred from the n side to the p side, two photons are emitted. When the two electrons of a Cooper pair are transported through different QDs, polarization-entangled photons are created, provided that the Cooper pairs retain their spin singlet character while being spatially separated on the two QDs. We show that a Clauser-Holt-Shimony-Horne (CHSH) Bell-type measurement is able to detect the entanglement of the photons over a broad range of microscopic parameters, even in the presence of parasitic processes and imperfections. © 2015 American Physical Society.


Park S.,TU Braunschweig | Recher P.,TU Braunschweig | Recher P.,Laboratory for Emerging Nanometrology Braunschweig
Physical Review Letters | Year: 2015

A phase from an adiabatic exchange of Majorana bound states (MBS) reveals their exotic anyonic nature. For detecting this exchange phase, we propose an experimental setup consisting of a Corbino geometry Josephson junction on the surface of a topological insulator, in which two MBS at zero energy can be created and rotated. We find that if a metallic tip is weakly coupled to a point on the junction, the time-averaged differential conductance of the tip-Majorana coupling shows peaks at the tip voltages eV=±(α-2πl)/TJ, where α=π/2 is the exchange phase of the two circulating MBS, TJ is the half rotation time of MBS, and l an integer. This result constitutes a clear experimental signature of Majorana fermion exchange. © 2015 American Physical Society.


Schroer A.,TU Braunschweig | Silvestrov P.G.,TU Braunschweig | Recher P.,TU Braunschweig | Recher P.,Laboratory for Emerging Nanometrology Braunschweig
Physical Review B - Condensed Matter and Materials Physics | Year: 2015

Bilayer graphene hosts valley-chiral one-dimensional modes at domain walls between regions of different interlayer potential or stacking order. When such a channel is close to a superconductor, the two electrons of a Cooper pair, which tunnel into it, move in opposite directions because they belong to different valleys related by the time-reversal symmetry. This kinetic variant of Cooper pair splitting requires neither Coulomb repulsion nor energy filtering but is enforced by the robustness of the valley isospin in the absence of atomic-scale defects. We derive an effective normal/superconducting/normal (NSN) model of the channel in proximity to an s-wave superconductor, calculate the conductance of split and spin-entangled pairs, and interpret it as a result of local Andreev reflection, in contrast to the widespread identification of Cooper pair splitting with crossed Andreev reflection in an NSN geometry. © 2015 American Physical Society.

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