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Quantum coherent and soft matter systems

English title Quantum coherent and soft matter systems
Applicant Blatter Johann W.
Number 178850
Funding scheme Project funding (Div. I-III)
Research institution Institut für Theoretische Physik ETH Zürich
Institution of higher education ETH Zurich - ETHZ
Main discipline Theoretical Physics
Start/End 01.05.2018 - 31.01.2021
Approved amount 595'285.00
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All Disciplines (2)

Theoretical Physics
Condensed Matter Physics

Keywords (12)

Josephson junctions; quantum thermodynamics; mesoscopic systems; superconductors; strongly correlated photons; Graphene; transport; vortex matter; quantum metrology; phase transitions; superfluids; disordered systems

Lay Summary (German)

Atome, Elektronen, und Photonen sind die mikroskopischen Teilchen aus denen wir Materialien und Bauelemente erschaffen. In unserer Forschungsarbeit untersuchen und optimieren wir neue Materialien und nutzen moderne technologische Konzepte zur Implementation neuartiger, funktionaler Bauelemente.
Lay summary
Wir untersuchen künstliche und natürliche Festkörper-Systeme mit dem Ziel, Materialien zu verstehen und zu optimieren, neue Materie-Zustände zu finden, und mit diesem Wissen Bauelemente mit neuen Funktionalitäten zu entwerfen. In unserer Forschungsarbeit betrachten wir sowohl elementare Teilchen, zum Beispiel Elektronen, Photonen, und Atome, als auch komplexere Bausteine von weicher Materie, zum Beispiel Polymere, Flusslinien in Supraleitern, oder Domänenwände in geordneten Materialien. Aktuelle Themen in der elektronischen mesoskopischen Physik sind künstliche Atome die mittels elektronischer Kavitäten verkoppelt sind; Systeme dieser Art könnten als Bausteine in einem Quanten Computer dienen. Ein Beispiel zu neuen Eigenschaften von Materialien sind unsere Arbeiten zum Graphene: gibt man solch eine einzelne Schicht von Kohlenstoff Atomen auf ein geeignetes Substrat, so entwickeln seine Elektronen neuartige, sogenannt typologische Eigenschaften, welche Randzustände erzeugen. Diese eindimensionalen leitenden Kanäle könnten wiederum Anwendungen in neuartigen Bauelementen finden. Materialien aus Licht und/oder Atomen zu erzeugen ist eine neue Idee die modernste Technologien nutzt. In unserer Arbeit untersuchen wir künstliche periodische Strukturen welche Photonen, also Quanten von Licht, einfangen und damit einen Kristall aus Licht definieren der interessante Eigenschaften zeigt. Schliesslich untersuchen wir auch das Verhalten weicher Materie, in unserem Fall von Flusslinien in Supraleitern, die sich wiederum in einem Kristall arrangieren. Die Bewegung dieser Flusslinien zerstört die supraleitende Eigenschaft des Materials. Abhilfe schaffen die Materialdefekte im Supraleiter welche die Flusslinien halten. Mit unserer Arbeit tragen wir zur Optimierung der Flusslinien Verankerung bei und damit zur Verbesserung der Transporteigenschaften dieser Materialklasse.  
Direct link to Lay Summary Last update: 09.04.2018

Lay Summary (English)

Atoms, electrons, and photons are the constituents from which we can build materials and devices. In our research, we study and optimise the properties of materials and engineer systems to implement new artificial materials and functional devices.
Lay summary

The basis of the physical world apparent to us are atoms, electrons, and photons. Atoms and free- or bound electrons
constitute the materials we use in everyday life, while photons are omnipresent in the form of light, heat, but also radio signals or X-rays. In materials science, we study numerous assemblies of atoms, electrons, and photons: cold atoms trapped in optical lattices provide us with novel simulators for exotic matter, as do photons in cavity arrays that are pumped by external fields and brought into interaction by nonlinearities in the cavities, e.g., due to a dielectric, or, more recently, an artifical atom or qubit.  A typical example in our work is the study of strongly interacting photons hopping in a lattice of non-linear cavities, for which we found a van der Waals type gas--liquid phenomenology.  A different approach is taken in mesoscopic physics, where specially grown semiconductor material is structured to fabricate atoms or qubits, the basic constituents of a quantum computer. We have recently studied, together with experimental colleagues, a dot--cavity system that can be used to interconnect different qubits using electronic wispering gallery modes as a communication bus. Qubits also can be used to build quantum thermodynamic engines with astonishing properties that relate to the second law of thermodynamics.  Indeed, we have proposed such an engine involving a quantum Maxwell demon (or actually angel) that fully converts heat into work when provided with pure quantum states. Finally, superconducting materials owe their functionality to the quantum phenomenon of Cooper pair formation and their condensation. In our work, we are interested in the phenomenology of such material when it is used to transport electric current without dissipation.  Vortices, thin magnetic flux lines penetrating the superconductor produce dissipation when driven by a current, and their immobilization is crucial for the functionality of the material. Our theory of strong pinning helps to quantitatively understand and optimize superconducting material for technological applications.
Direct link to Lay Summary Last update: 09.04.2018

Responsible applicant and co-applicants


Associated projects

Number Title Start Funding scheme
159238 Quantum coherent and soft matter systems 01.05.2015 Project funding (Div. I-III)


We investigate artifical and natural condensed matter systems with the goal to find novel devices, discover and characterise novel phases, and understand and optimize material functionality. In our work, we deal with microscopic (electronic, atomic, photonic), and soft matter (vortices in superconductors) degrees of freedom. Starting from individual devices, we study electronic properties of mesoscopic structures, in particular, coupled dot--cavity systems implemented in 2D high-mobility electron gases, where our interest focuses on their optimized design, their characterisation through transport spectroscopy, the fundamental understanding of their functionality, as well as potential applications in quantum engineering. A particular aspect we study is the Kondo box problem that naturally appears in these systems due to the discrete spectrum defined by cavity states. Graphene provides a natural 2D electronic system that exhibits high mobility if deposited on a suitable substrate, e.g., hexa boron nitride; we investigate various aspects of the substrate-induced changes in the electronic properties of this setup. Photons in non-linear cavity arrays emulate traditional condensed matter systems but contribute new features as they naturally reside out of equilibrium, being pumped and lossy.In our work on such coupled arrays, we are mainly interested in effects of strong photon correlations that generate novel non-equilibrium photonic phases and transitions between them. Another aspect of strongly coupled light--matter physics we are interested in is the Dicke transition, where we want to better understand the conditions for the appearance of a superradiant phase. When studying vortex matter in type II superconductors, our main interesttoday is in the theory of strong pinning. While the obiquitous weak collective pinning theory has been developed over decades, particularly in the wake of the high-Tc discovery, much less is known about the theory of strong pinning. We have set up a research program that develops the strong pinning scenario, originally due to Labusch, with several milestones achievedalready, the calculation of critical currents, vortex dynamics and current-voltage characteristics, ac-response, and more results to come, among those are vortex depinning and creep and the transition from strong to weak pinning.