Grégory Strübi


Department of Physics
University of Basel
Klingelbergstrasse 82
CH-4056 Basel, Switzerland

email:view address


Short CV

Since April 2010 PhD student under the supervision of Christoph Bruder
2010 Master of Physics at the EPFL


Show all abstracts.

1.  Point contacts and localization in generic helical liquids
Christoph P. Orth, Grégory Strübi, and Thomas L. Schmidt.

We consider two helical liquids on opposite edges of a narrow two-dimensional topological insulator, which are connected by one or several local tunnel junctions. In the presence of spatially inhomogeneous Rashba spin-orbit coupling, the spin textures of the helical states on opposite edges are different. We demonstrate that this has a strong impact on the electron transport between the edges. In particular, in the case of many random tunnel contacts, the localization length depends strongly on the spin textures of the edge states.

2.  Measuring Ultrasmall Time Delays of Light by Joint Weak Measurements
Grégory Strübi (University of Basel) and Christoph Bruder (University of Basel).
Phys. Rev. Lett. 110, 083605 (2013).; arXiv:1301.5846.

We propose to use weak measurements away from the weak-value amplification regime to carry out precision measurements of time delays of light. Our scheme is robust to several sources of noise that are shown to only limit the relative precision of the measurement. Thus, they do not set a limit on the smallest measurable phase shift, contrary to standard interferometry and weak-value-based measurement techniques. Our idea is not restricted to phase-shift measurements and could be used to measure other small effects using a similar protocol.

3.  Interferometric and Noise Signatures of Majorana Fermion Edge States in Transport Experiments
Grégory Strübi (University of Basel), Wolfgang Belzig (Universität Konstanz), Mahn-Soo Choi (Korea University, Seoul), and Christoph Bruder (University of Basel).
Phys. Rev. Lett. 107, 136403 (2011).; arXiv:1109.0393.

Domain walls between superconducting and magnetic regions placed on top of a topological insulator support transport channels for Majorana fermions. We propose to study noise correlations in a Hanbury Brown–Twiss type interferometer and find three signatures of the Majorana nature of the channels. First, the average charge current in the outgoing leads vanishes. Furthermore, we predict an anomalously large shot noise in the output ports for a vanishing average current signal. Adding a quantum point contact to the setup, we find a surprising absence of partition noise which can be traced back to the Majorana nature of the carriers.

4.  Vison excitations in near-critical quantum dimer models
Grégory Strübi and Dmitri A. Ivanov.
EPL 94, 57003 (2011); arXiv:1009.1040.

We study vison excitations in a quantum dimer model interpolating between the Rokhsar-Kivelson models on the square and triangular lattices. In the square-lattice case, the model is known to be critical and characterized by U(1) topological quantum numbers. Introducing diagonal dimers brings the model to a Z_2 resonating-valence-bond phase. We study variationally the emergence of vison excitations at low concentration of diagonal dimers, close to the critical point. We find that, in this regime, vison excitations are large in size and their structure resembles vortices in type-II superconductors.