Condensed Matter Seminars

Spin ice: at the dawn of a new day?

Speaker: 
Michel Gingras, Department of Physics & Astronomy, University of Waterloo
Event Date and Time: 
Thu, 2015-01-29 14:00 - 15:00
Location: 
Hennings 318
Local Contact: 
Marcel Franz
Intended Audience: 
Graduate

Spin ices are frustrated ferromagnetic systems which are fascinating for the many aspects of statistical mechanics that they embody.

Novel Josephson effect in triplet Josephson junctions: The story begins

Speaker: 
Dirk Manske, Max Planck Institute for Solid State Research
Event Date and Time: 
Thu, 2015-01-15 14:00 - 15:00
Location: 
Hennings 318
Intended Audience: 
Graduate

Josephson junctions with magnetic tunneling barriers provide an excellent opportunity to observe the interplay of ferromagnetism and superconductivity in a controlled setting.

Specific heat of underdoped cuprate superconductors in high magnetic fields

Speaker: 
Jonathon Kemper, National High Magnetic Field Laboratory, University of Florida
Event Date and Time: 
Mon, 2014-12-01 12:00 - 13:00
Location: 
AMPEL 311
Local Contact: 
Andrea Damascelli
Intended Audience: 
Graduate
I will discuss specific heat measurements on three families of hole-doped cuprate superconductors, including YBa2Cu3O6+x where x=0.43, 0.47,0.51 and 0.67, aimed at tracking the low energy electronic density of states as a function of magnetic field in both the superconducting and resistive state. The underlying goal is one of understanding how superconducting state at zero field evolves into one with strong Fermi liquid signatures in the high field resistive state, such as quantum magneto-oscillations.

Emergent SU(4) Kondo physics in a spin-charge-entangled double quantum dot

Speaker: 
Andrew Keller, Stanford University
Event Date and Time: 
Fri, 2014-12-05 10:00 - 11:00
Location: 
Hennings 318
Local Contact: 
Maria Pylaeva
Intended Audience: 
Graduate

Quantum impurity models, which describe how a local degree of freedom interacts with a continuum, are central to condensed-matter physics. Such models may be naturally implemented with quantum dots coupled to each other and to metallic leads. Here we detail a many-body Kondo state occurring when two quantum dots are coupled electrostatically. We use orbital state-resolved bias spectroscopy to demonstrate the entanglement of spin and charge between spatially separated orbitals of the Kondo state.

Phase lapses and dephasing in quantum Hall interferometers

Speaker: 
Yehuda Dinaii, Weizmann Institute
Event Date and Time: 
Thu, 2014-12-04 14:00 - 15:00
Location: 
Hennings 318
Local Contact: 
Marcel Franz
Intended Audience: 
Graduate

In this talk I will discuss the phenomena of dephasing and phase lapses as they occur in two setups operating in the quantum Hall regime. Both setups consist of a quantum dot and an electronic Mach-Zehnder interferometer. Dephasing, i.e. loss of coherent transport, and phases lapses, i.e. abrupt jumps in the phase of the transmission amplitude, turn out to be intimately related in these setups. In the first setup, transport through a chiral channel is affected by charge fluctuations in a nearby quantum dot.

Extraordinary Acoustic Raman (EAR): Listening in on Nanoparticle Vibrations

Speaker: 
Reuven Gordon, University of Victoria
Event Date and Time: 
Thu, 2014-11-20 14:00 - 15:00
Location: 
AMPEL 311
Local Contact: 
Jeff Young
Intended Audience: 
Graduate

Colloidal quantum dots, viruses, DNA and all other nanoparticles have acoustic vibrations that can act as ‘fingerprints’ to identify their shape, size and mechanical properties, yet high-resolution Raman spectroscopy in this low-energy range has been lacking. Here, we introduce extraordinary acoustic Raman (EAR) spectroscopy, a new technique to measure the Raman-active vibrations of single isolated nanoparticles in the 0.1–10 wavenumber range with ∼0.05 wavenumber resolution.

Thermal and electrical transport in the heavy fermion compound YbRh2Si2 under magnetic fields

Speaker: 
Heike Pfau, Max Planck Institute for Chemical Physics of Solids, Dresden
Event Date and Time: 
Thu, 2014-11-13 14:00 - 15:00
Location: 
Hennings 318
Local Contact: 
Andrea Damascelli
Intended Audience: 
Graduate

The Kondo effect couples a local magnetic moment with conduction electrons to a composite heavy quasiparticle leading to a non-magnetic ground state. At the same time, a coupling between the moments favors a magnetically ordered state. An applied magnetic field influences the ground state and the nature of the heavy quasiparticles in two ways: On one side, it can tune the competition between the Kondo interaction and the magnetic exchange leading to a quantum critical point (QCP).

Femtosecond broadband ellipsometry and magneto-optics: disentanglement of spin and charge dynamics

Speaker: 
Fabio Boschini, Politecnico di Milano
Event Date and Time: 
Thu, 2014-11-06 14:00 - 15:30
Location: 
Hennings 318
Local Contact: 
Andrea Damascelli
Intended Audience: 
Undergraduate

 

Interplay of disorder, nematicity and magnetism in Fe-based Superconductors

Speaker: 
Peter Hirschfeld, University of Florida
Event Date and Time: 
Thu, 2014-10-02 14:00 - 15:00
Location: 
Hennings 318
Intended Audience: 
Graduate
Impurities can nucleate local magnetic states and give rise to quasi-long-range magnetic order in correlated electron systems. In the Fe-based superconductors, stripe-like (pi,0) order usually prevails in parent compounds, but competes with (pi,pi) antiferromagnetism. I show that in such a situation, unusual emergent defect states (``nematogens") can be created by nonmagnetic impurities which strongly break C4 symmetry and may be responsible for local nematic defect structures observed by STM, as well as for the transport anisotropy observed in these materials.

Crystal symmetry and properties of low dimensional epitaxial oxides; interfaces and superlattices

Speaker: 
Gertjan Koster, University of Twente, MESA+ Institute for Nanotechnology
Event Date and Time: 
Mon, 2014-08-18 11:00 - 12:00
Location: 
AMPEL 311
Local Contact: 
Andrea Damascelli
Intended Audience: 
Graduate

In complex oxide materials the occurrence of ferroelectric, ferromagnetic or other properties are for the most part determined by the detailed oxygen coordination of metal cations. More specifically, in the case of perovskite-type materials ABO3, where A and B are metal cations, by the BO6 octahedral orientations and rotations. At interfaces in epitaxial oxide hetero structures, for example magnetic junctions or capacitive structures, this oxygen sub-lattice is found to be different from its bulk counterpart.

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