Condensed Matter Seminar

semester, 2010


Wednesday, January 13th 2010
10:00 am:
Speaker: Professor L. Belova, KTH Royal Institute of Technology
Subject: InkJet technology for flexible patterning of functional materials
Note change in time, day and place of Condensed Matter Seminar, this week only.

With the development of nanoscience and methods of design and fabrication of nanomaterials the availability of inexpensive easy to use tools capable of large area patterning of nanoscale materials and structures is becoming increasingly important. InkJet technology has been developing rapidly over the last decade for high-resolution photo printing and has now expanded into patterning of functional materials. Piezoelectrically driven InkJets operate at room temperature in ambient conditions and thus are compatible with a wide variety of materials from ceramic and magnetic nanoparticles to carbon nanotubes and proteins. A variety of substrates from paper to glass and plastics can be used. Some of our recent developments are related to direct patterning of oxides (e.g. ZnO, MgO) for optics and magneto-optic components. One of the targeted applications is UV sensing.


Thursday, January 14th 2010
7:30 pm:
Speaker: Kevin O'Grady, The University of York
Subject: A New Paradigm for Exchange Bias in Polycrystalline Films
Pizza will be served before the lecture.

The phenomenon of exchange bias has remained something of a mystery since it was discovered in core-shell particles in 1956 [1]. Over the subsequent years many different models have been proposed to explain this effect, most of which agree with some experimental data that can be found in the literature. No single theory, however, has been able to explain the data consistently for different systems.

In this lecture the reason for our inability to explain exchange bias will be reviewed, and a new paradigm to explain the phenomenon in sputtered polycrystalline films will be presented. This new paradigm is based on an original granular model described by Falcomer and Charap [2]. Its premise is that very careful thermal and magnetic cycling is required to ensure that the order in the antiferromagnetic grains is controlled. Without such careful control, reproducible data cannot be obtained.


Thursday, January 28th 2010
1:25 pm:
Condensed Matter Seminar in 210 Physics
Speaker: Professor Baruch Meerson, Racah Institute of Physics, Hebrew University of Jerusalem
Subject: Large fluctuations in stochastic population dynamics

Since the celebrated book of T. R. Malthus ``An Essay on the Principle of Population"(Murray, London, 1798), quantitative modeling of population dynamics has attracted much interest from scientists and the general public. To a large extent this interest is powered by the dangers of two extreme types of population behavior. One is a sudden extinction of a long-lived self-regulating population. The other is an unlimited proliferation of a population:
a Malthusian catastrophe. For relatively small populations, each of these can be sparked by a rare large fluctuation coming from the intrinsic discreteness of the population and stochastic
character of birth-death processes. A similar set of problems involves extinction of disease from a community. I will show how one can use a variant of WKB approximation to calculate the mean
time to extinction (or explosion) of a stochastic population.


Thursday, February 4th 2010
1:25 pm:
Condensed Matter Seminar in 210 Physics
Speaker: C. Professor Daniel Frisbie, Department of Chemical Engineering and Materials Science
Subject: Electrical Double-Layer Transistors – A Strategy for Examining Surface Conduction at Carrier Densities Above 1014 cm-2

Transistors with electrolyte gates are termed ‘electrical double-layer transistors’ and are proving to be very interesting structures for transport measurements because of the very large 2D carrier densities that can be achieved. When a liquid electrolyte is sandwiched between metal plates, application of a voltage to the plates results in motion of the ions to screen the electrical field. To first order, this sets up double layers at both plate/electrolyte interfaces in which a sheet of electronic charge in the metal is balanced by a sheet of oppositely charged ions in the electrolyte. The capacitance of these very thin (~1 nm) double layers is enormous, >10 F/cm2. In a similar fashion, the large capacitance of electrolytes may be exploited in an EDLT to induce very large hole or electron densities at the surface of a semiconductor in contact with electrolyte. With an EDLT it is possible to study transport in a variety of materials at gate-tunable carrier densities ranging from 1012 to >1014 cm-2; these densities are large enough in principle to examine the metal-insulator transition and the onset of superconductivity in specific systems. In this talk I will describe a fascinating and relatively new class of electrolytes termed room temperature ionic liquids and discuss their application in EDLTs, especially EDLTs based on organic semiconductors.


Thursday, February 11th 2010
1:25 pm:
Condensed Matter Seminar in 210 Physics
Speaker: Alexander Chudnovskiy, The University of Hamburg
Subject: Double quantum dot as a detector of charge fluctuations

Absorption of energy quanta generated by a quantum point contact results in the inelastic current through a double quantum dot placed nearby. This allows to use double quantum dot as a detector of non-equilibrium charge fluctuations. In contrast to a single quantum dot, the inelastic current through the double quantum dot is determined by the non-local current correlations in the quantum point contact, which results in its sensitivity to the energy dependence of the quantum point contact transmission and can lead to suppression of the inelastic current for a substantial range of transport voltages on the quantum point contact. We calculate the inelastic current as a function of microscopic parameters of the circuit.


Thursday, February 18th 2010
1:25 pm:
Condense Matter Seminar in 210 Physics
Speaker: Guillaume Chabot-Couture (Department of Applied Physics, Stanford University)
Subject: Synchtrotron X-ray scattering studies of anomalous oxygen order in superconducting HgBa2CuO4+d and of charge-transfer excitations in related undoped cuprates

The first part of this talk describes the discovery of an anomalous oxygen chain order in the model high-temperature superconductor HgBa2CuO4+d using X-ray diffraction. The order's temperature dependence indicates an anomalous involvement of the crystal lattice, whereas its doping dependence suggests links to the magnetic and electronic phase diagram. In the second part, we describe a of study charge-transfer excitations in
undoped cuprates using resonant inelastic X-ray scattering (RIXS) at the Cu K-edge. Within an extended third-order perturbation model, we interpret photon polarization dependence measurements in terms of excitations with different symmetries. By comparing the momentum-dependent inelastic spectra of undoped cuprates collected for different resonant conditions, we observe a universal set of inelastic features and argue that they
characterize the electronic structure of the copper-oxygen planes.


Thursday, February 25th 2010
1:25 pm:
Condensed Matter Seminar in 210 Physics
Speaker: Alexander Efros, Naval Research Laboratory, Washington, DC
Subject: Electron spin manipulation in an ensemble of singly charged quantum dots

Fast dephasing of electron spins in an ensemble of quantum dots is detrimental for applications in quantum-information processing. We show that dephasing can be overcome by using a periodic train of light pulses to synchronize the phases of the precessing spins, and demonstrate this effect in an ensemble of singly charged (In,Ga)As/GaAs quantum dots [1]. We first discuss the physical mechanism of this synchronization in a quantum-dot ensemble [2, 3]. A periodic train of circularly polarized light pulses from a mode-locked laser synchronizes the precession of the spins to the laser repetition rate, transferring the mode-locking into the spin system. The mode-locking technique allows us to measure the single-spin coherence time to be 3 microseconds [1], which is four orders of magnitude longer than the ensemble dephasing time of 400 picoseconds. The technique also offers the possibility of achieving all-optical coherent manipulation of spin ensembles, in which electron spins can be clocked by two trains of pump pulses with a fixed temporal delay. After this pulse sequence, the quantum-dot ensemble shows multiple bursts of Faraday rotation signals, whose repetition period agrees well with developed theory. The nuclei in these experiments act constructively, leading to the nuclear-induced frequency-focusing effect, which moves the electron-spin precession into dephasing-free subspace [4]. This effect has the potential for focusing all precession frequencies of the quantum-dot ensemble to a single precession mode [5].

[1] A. Greilich, D. R. Yakovlev, A. Shabaev, Al. L. Efros, I. A. Yugova, R. Oulton, V. Stavarache, D. Reuter, A. Wieck, and M. Bayer, Science 313, 341 (2006).[2] A. Greilich, R. Oulton, E. A. Zhukov, . A. Yugova, D. R. Yakovlev, M. Bayer, A. Shabaev, Al. L. Efros, I. A. Merkulov, V. Stavarache, D. Reuter, and A. Wieck, Phys.Rev. Lett., 96, 227401 (2006). [3] A. Shabaev, Al. L. Efros, D. Gammon, and I. A. Merkulov, Phys. Rev. B 68, 201305(R) (2003). [4] A. Greilich, A. Shabaev, D. R. Yakovlev, Al. L. Efros, I. A. Yugova, D. Reuter, A. D. Wieck, and M. Bayer, Science 317, 1896 (2007). [5] A. Greilich, D. R. Yakovlev, Al. L. Efros, I. A. Yugova, D. Reuter, A. D. Wieck, and M. Bayer, Phys. Rev. B 79, 201305 (R) (2009).


Thursday, March 4th 2010
1:25 pm:
Condensed Matter Seminar in 210 Physics
Speaker: Marco Peloso, University of Minnesota
Subject: Motivations and tests of cosmological inflation

It is commonly stated that the universe started very small with a very high temperature. Most of the present day cosmologists actually believe that this ``hot big-bang'' era was preceded by a stage of extremely rapid expansion, in which the universe was essentially cold and empty of ordinary matter and radiation. This paradigm allows to solve several severe problems of big-bang cosmology and makes some definite prediction on the generation and the properties of the primordial perturbations (the seeds of galaxies). Such predictions are in excellent agreement with observations. I will first review these problems, and discuss how inflation solves them. I will then discuss what the predictions, and the observations, are. If time permits, I will also mention some unexplained features in the latest data which, if of cosmological origin, may require some modification to the simplest models of inflation.


Thursday, March 11th 2010
1:25 pm:
Condensed Matter Seminar in 210 Physics
Speaker: Yen-Hsiang Lin, PiDong Pan, Eric Garlid, Steve Snyder
Subject: March Meeting practice talks

Thursday, March 18th 2010
1:25 pm:
Condensed Matter Seminar in 210 Physics
There will be no seminar this week.

Thursday, March 25th 2010
1:25 pm:
Condensed Matter Seminar in 210 Physics
Speaker: Ivan Dmitriev, Karlsruhe Institute of Technology (KIT), Institute of Nanotechnology
Subject: Resonant magneto-transport in non-equilibrium 2DES in high Landau levels

Thursday, April 1st 2010
1:25 pm:
Condensed Matter Seminar in 210 Physics
Speaker: Professor Vincent Noireaux, University of Minnesota
Subject: Constructive approach to gene expression with a cell-free toolbox.

In the past 10 years, advances in molecular biology have led to the emergence of systems biology and synthetic biology. These new research areas aim at understanding the information structure of living systems such as gene regulatory networks and their dynamics. Many experimental approaches have been developed to study the different aspects of the flow of information in biological systems. While most of the studies are performed in vivo or in silico, only a few cell-free approaches have been proposed.
I will present a constructive approach to DNA information processes which consists of a toolbox to express genes outside living organisms. I will discuss how the toolbox is prepared and how it is used to tackle quantitative and biophysical aspects of gene expression by giving a few examples. I will conclude with the possibility of using this approach to build a synthetic cell starting from the basic molecules.


Thursday, April 8th 2010
1:25 pm:
Condensed Matter Seminar in 210 Physics
Speaker: A. Mobius Leibniz Institute for Solid State and Materials Research Dresden, Germany
Subject: Phenomenological aspects of the metal-insulator transition in disordered systems: So, was Mott right after all?

Metal-insulator transitions in disordered systems have attracted much interest for fifty years. Milestones on this way were the concepts of Anderson localization, of Mott's minimum metallic conductivity, the scaling theory of localization, and the renormalization approach incorporating electron-electron interaction. Nevertheless, important questions have not been finally settled yet: The comparison between experiment and theory suffers from the limitation of the temperature range and the influence of theoretical biases. Hence empirical data
exploration and construction of phenomenological models can be very helpful in discriminating between theoretical hypotheses. In the talk, it is demonstrated that, for three-dimensional systems, the behavior of derivatives often supports the idea of the minimum metallic conductivity, in contrast to conventional wisdom disclaiming it due to usual fits. Moreover, indications for a finite-temperature transition between activated and apparently metallic conduction in two-dimensional systems are discussed.


Thursday, April 15th 2010
1:25 pm:
Condensed Matter Seminar in 210 Physics
Speaker: Professor Albert Libchaber, The Rockefeller University, NYC
Subject: How Do Bacteria Adapt to Temperature and Oxygen?

The response of E-coli bacteria to environment changes can take different forms such as, modifying their gene expression profile or altering their swimming pattern. The response to a temperature gradient depends on previous growth conditions of bacteria—the bacteria swimming towards warm or cold regions, depending on their growth concentration. Such extreme behavior is related to change in the sensitivity and concentration of their heat-sensing-receptors. In response to oxygen gradients, the bacteria can switch from motile to non-motile. The state of the proton potential across the bacterial wall depends on the oxygen level and thus affects motility.


Thursday, April 22nd 2010
1:25 pm:
Condensed Matter Seminar in 210 Physics
Speaker: Chandra Varma, UC Riverside
Subject: Collective modes observed and yet to be observed in the Loop Ordered Phase of High Temperature Superconductors.

Recently Greven et al. have observed, through inelastic polarized neutron experiments, weakly dispersion collective modes in a family of high temperature superconductors in the same region of the phase diagram in which they previously observed elastic scattering consistent with the predicted Loop Ordered State. I will present the theory for the collective modes and point out that two other classes of collective modes should also be observed. The observations and the theory also serve to resolve some important issues regarding the ground state in underdoped Cuprates.


Thursday, April 29th 2010
1:25 pm:
Condensed Matter Seminar in 210 Physics
Speaker: Professor Igor Kukushkin (Institute for Solid State Physics, Chernogolovka, Russia)
Subject: "Microwave spectroscopy of neutral and charged double layer electron-hole systems"

Thursday, May 6th 2010
1:25 pm:
Condensed Matter Seminar in 210 Physics
There will be no seminar this week.

Monday, May 10th 2010
3:35 pm:
Speaker: Magnetic Interactions in Perovskite Oxide Superlattices
Subject: Yayoi Takamura, University of California Davis
Sponosored by the University of Minnesota Materials Research Science and Engineering Center

Thursday, May 13th 2010
1:25 pm:
Special Condensed Matter Seminar in 435 Physics (Note the room change!)
Speaker: Professor Joel E. Moore, University of California, Berkeley
Subject: New Topologically Ordered Phases of Condensed Matter

Much of condensed matter physics is concerned with understanding how different kinds of order emerge from interactions between a large number of simple constituents. In ordered phases such as crystals, magnets, and superfluids, the order is understood through "symmetry breaking": in a crystal, for example, the continuous symmetries of space under rotations and translations are not reflected in the ground state. A major discovery of the 1980s was that electrons confined to two dimensions and in a strong magnetic field exhibit a completely different, "topological" type of order that underlies the quantum Hall effect. A discovery in the last few years is that topological order also occurs in some three-dimensional materials, dubbed "topological insulators", in zero magnetic field. Spin-orbit coupling, an intrinsic property of all solids, drives the formation of the topological state. This talk will explain what topological order means, how topological insulators were discovered, and how they realize the "axion electrodynamics" studied by particle physicists in the 1980s. Two possible applications of these new materials are discussed in closing.


Friday, May 14th 2010
11:00 am:
Condensed Matter Seminar in 435 Physics
Speaker: Professor Joel E. Moore, University of California, Berkeley
Subject: Applications of entanglement entropy to quantum criticality

Monday, June 28th 2010
11:00 am:
Speaker: Yves Adjallah, University of Minnesota
Subject: Electronic transport in mixed-phase hydrogenated amorphous/nanocrystalline silicon thin films
This is the public portion of Mr. Adjallah's Ph.D. final oral exam.

Thursday, August 19th 2010
3:30 pm:
Thesis Defense in 435 Physics
Speaker: A. Emir Gumrukcuoglu, University of Minnesota
Subject: Coupled Quantum Systems in Inflationary Cosmology

Thursday, September 9th 2010
1:25 pm:
Condensed Matter Seminar in 210 Physics
Speaker: Austen Lamacraft, University of Virginia
Subject: Hamiltonian monodromy in a spin-1 Bose gas.

In the 1980s mathematicians noticed that a number of simple integrable mechanical systems display the phenomenon of Hamiltonian monodromy, meaning that action-angle coordinates cannot be defined globally in the phase space of the problem. This rather abstract discovery has more recently begun to garner the attention of physicists -- particular those interested in molecular spectra -- following the realization that it has
striking consequences for the spectrum of the system following
quantization.

In this talk I will try to give an introduction to these ideas, and give a realization of this phenomenon in a condensed matter system: a Bose condensate of spin-1 atoms.


Thursday, September 16th 2010
1:25 pm:
Condensed Matter Seminar in 210 Physics
Speaker: Chandan Dasgupta
Subject: Growing length and time scales in glass forming liquids

Thursday, September 23rd 2010
1:25 pm:
Condensed Matter Seminar in 210 Physics
Speaker: Alex Levchenko, Argonne National Lab
Subject:  Interacting electrons in 1D beyond the Luttinger-liquid limit: transport and relaxation

I will present scattering theory of one-dimensional electrons in
quantum wires that is beyond the scope of Luttinger-liquid model. For applications I will discuss transport properties (electrical and thermal conductance, thermoelectric effects) and also origin of electronic relaxation due to three-particle collisions.


Thursday, September 30th 2010
1:25 pm:
Condensed Matter Seminar in 210 Physics
Speaker: Jenny Hoffman, Harvard University
Subject: Nanoscale Explorations of the Insulator-Metal Transition in Vanadium Dioxide

It has been known for over 50 years that vanadium dioxide (VO2) undergoes a simultaneous structural and insulator-to-metal transition as a function of either temperature or strain. The last few years have brought VO2 research back to the forefront, with evidence that the transition may also be triggered by electric field, and that the structural and electronic transitions may be separable. I will provide an overview of VO2 research and applications, and discuss our nanoscale explorations of this material. We use a conducting atomic force microscope to demonstrate controlled local phase switching of a VO2 film. Our imaging technique opens up the possibility for an understanding of the microscopic mechanism of phase transition in VO2 as well as its potential relevance to novel solid state devices.


Thursday, October 7th 2010
1:25 pm:
Condensed Matter Seminar in 210 Physics
Speaker: Joel E. Moore, Berkeley
Subject: Optical signatures of spin transport, Berry's phase, and unconventional superconductivity

This talk presents three examples of how optical methods can supply unique information about spin and correlation physics even in nonmagnetic materials. The first is the use of circularly polarized light to create artificial short-lived magnetic states, which enabled the observation of "spin Coulomb drag". The second is the existence of photocurrents (linear in intensity, hence nonlinear in electric field) that switch with the helicity of incident light. This effect has been studied
experimentally for a decade but not well understood theoretically; our theoretical results suggest that a Berry phase effect in transport of nonmagnetic metals may explain these experiments, at least for terahertz incident frequencies.
We close by reviewing progress and commenting on future directions in linear and nonlinear optical probes of superconductors and other correlated states.


Thursday, October 14th 2010
1:25 pm:
Condensed Matter Seminar in 210 Physics
Speaker: Maxim Khodas, Brookhaven National Lab and Iowa State U.
Subject: Effect of order parameter fluctuations on the spectral density in d-wave superconductors

My talk contains two related parts. In the first part I will discuss the spectral density in 2D d-wave superconductors in the regime of strong quantum fluctuations. I will start with the motivation based on Angular Resolved Photo-Emission Experiments.
The theoretical model is then presented to capture the effects of phase fluctuations without specifying the paring mechanism I discuss the solution of the model and give results for the spectral function. In the second part I will discuss the Fermi Surface Reconstruction and underlying mechanism related to the anti-ferromagnetic fluctuations. I will show how the pockets obtained on the mean field level are modified by the fluctuations of the staggered magnetization. Finally, I would conclude with a short summary.


Thursday, October 21st 2010
1:25 pm:
Condensed Matter Seminar in 210 Physics
Speaker: Ray Ashoori, MIT
Subject: Extremely high resolution spectroscopy of the two-dimensional electronic system

Friday, October 22nd 2010
10:00 am:
Speaker: Ray Ashoori, MIT
Subject: Capacitance and magnetization of the electronic system formed at the interface between two oxides
*Note the special time and location

Thursday, October 28th 2010
1:25 pm:
Condensed Matter Seminar in 210 Physics
Speaker: Evgeny Tsymbal, University of Nebraska-Lincoln
Subject: Perspectives of Ferroelectric and Multiferroic Tunnel Junctions

Tunnel junctions are electronic devices in which current-carrying electrons can quantum-mechanically be transmitted between two metal electrodes across a very thin insulating barrier layer. So far almost all the existing tunnel junctions were based on non-polar dielectrics. An exciting possibility to extend the functionality of tunnel junctions is to use a ferroelectric insulator as a barrier to create a ferroelectric tunnel junction (FTJ). [1] The key property of FTJ is a tunneling electroresistance (TER) effect that is a change in the electrical resistance of a FTJ with reversal of ferroelectric polarization. Functional properties of a FTJ can be further extended by using ferromagnetic metal electrodes to make a multiferroic tunnel junction (MFTJ). In a MFTJ the spin polarization of tunneling electrons and tunneling magnetoresistance (TMR) can be affected by ferroelectric polarization of the barrier. [1] Thus, MFTJs represent four-state resistance devices that can be controlled both by electric and magnetic fields due to a coexistence of TER and TMR effects. This talk will address the physics of FTJs and MFTJs based on our model and first-principles calculations. Recent experimental evidence of a giant TER effect and coexistence of TER and TMR in MFTJs will also be discussed.

1. E.Y. Tsymbal and H. Kohlstedt, Science 313, 181 (2006).


Thursday, November 4th 2010
1:25 pm:
Condensed Matter Seminar in 210 Physics
Speaker: Daniel Agterberg, University of Wisconsin, Milwaukee
Subject: Ginzburg Landau Wilson theories for FFLO superfluids and superconductors

With the groundbreaking work of Fulde, Ferrell, Larkin and Ovchinnikov (FFLO), it was realized that superconducting order can also break translational invariance, leading to a phase in which the Cooper pairs develop a coherent periodic spatially oscillating structure. Such pair density wave (PDW) superconductivity has become relevant in a diverse range of systems, including cuprates, organic superconductors, heavy fermion superconductors, cold atoms, and high-density quark matter. Here I discuss Ginzburg-Landau-Wilson theories of PDW/FFLO superconductors [1,2,3]. The emphasis will be on PDW ground state properties, on the vortex/dislocation topological defects of these ground states, and the consequences of these defects on the superconducting and superfluid states. In particular, novel phases such as translationally invariant charge four and charge six superfluid liquid crystals result from the thermal excitation of these defects.


Thursday, November 11th 2010
1:25 pm:
Condensed Matter Seminar in 210 Physics
Speaker: Dr. Neven Barisic, Stuttgart University
Subject: Electronic properties of iron-pnictides and cuprates

We have studied the electrodynamic properties of 122 iron-pnictide single crystals by dc resistivity and infrared spectroscopy. A novel analysis of the optical conductivity [1-4] allows the discrimination between two kinds of charge carriers. One kind exhibits a temperature-independent response with a large scattering rate. The second kind of carriers appears to govern the electrical properties. It becomes gapped due to the SDW transition in the parent materials and is responsible for the superconductivity in the doped compounds. Analyzing the dc resistivity, by separating these two conducting channels, reveals a T2 dependence over a wide temperature range. The apparent Fermi-liquid behavior imposes strong constrains on this class of materials. Superconducting fluctuations precede the superconducting long-range order and carry important information about the dimensionality of the superconducting phase. Although studied by various experimental techniques in the high-Tc cuprates, the onset temperature of the fluctuations has not yet been unambiguously determined. We are proposing a novel approach to microwave conductivity measurements that elucidates the phase diagram of the cuprates [5]. Measurements are performed on HgBa2CuO4+δ, which is considered to be a model compound [6]. It is shown that the superconducting fluctuations affect only a relatively narrow range of temperatures above Tc, of the order of 10 K. This quasi-3D regime strikingly contrasts with the strongly anisotropic quasi-2D normal state characterized by a very large anisotropy of the in- and out of plane conductivities.


Thursday, November 18th 2010
1:25 pm:
Condensed Matter Seminar in 210 Physics
Speaker: Boris Spivak, University of Washington, Seattle
Subject: Theory of normal-superconductor transitions and the Weakly Coupled Pfaffian as a Type I Quantum Hall Liquid.

We study suppression of superconductivity by disorder in superconductors. I the case of d-wave superconductors
there are two sequential low temperature transitions as a function of disorder: a d-wave to s-wave, and then an s-wave to metal transition. In the case of p-wave superconductors there only one superconductor-metal transition. The Pfaffian phase of electrons in the proximity of a half-filled Landau level is understood to be a p+ip superconductor of composite fermions. We consider the properties of this paired quantum Hall phase when the pairing scale is small, i.e. in the weak-coupling, BCS, limit, where the coherence length is much larger than the charge screening length. We find that, as in a Type I superconductor,
the vortices attract so that, upon varying the magnetic field from its magic value at \nu = 5/2, the system exhibits Coulomb frustrated phase separation. We propose that the weakly and strongly coupled Pfaffian states exemplify a general dichotomy between Type I and Type II quantum Hall fluid.


Thursday, November 25th 2010
1:25 pm:
Condensed Matter Seminar in 210 Physics
There will be no seminar this week. The University is closed for the Thanksgiving Holiday.

Thursday, December 2nd 2010
1:25 pm:
Condensed Matter Seminar in 210 Physics
Speaker: Peter Armitage, Johns Hopkins University
Subject: Ultrafast (but Many-Body) Relaxation in a Low-Density Electron Glass

After a review of the salient details of the AC transport and
relaxation effects in electronic glasses, I will present our recent study of the relaxation dynamics of the photoexcited conductivity of the impurity states in the low-density electronic glass, phosphorous- doped silicon Si:P. Using subband gap optical pump-terahertz probe spectroscopy we find strongly temperature- and fluence-dependent glassy power-law relaxation occurring over subnanosecond time scales. Such behavior is in contrast to the much longer time scales found in higher electron density glassy systems. We also find evidence for
both multiparticle relaxation mechanisms and/or coupling to electronic collective modes and a low temperature quantum relaxational regime.


Thursday, December 9th 2010
1:25 pm:
Condensed Matter Seminar in 210 Physics
Speaker: Prof. Claudia Felser, University of Mainz
To be announced.

Thursday, December 16th 2010
1:25 pm:
Condensed Matter Seminar in 210 Physics
There will be no seminar this week. Finals begin.

Thursday, December 23rd 2010
1:25 pm:
Condensed Matter Seminar in 210 Physics
No seminar, winter break.

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