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### Cancelled: PAN Seminar

Monday, October 30th, 201702:00 PM - 03:00 PM

Storrs Campus

Physics Building, P121

Holger Nielsen, Niels Bohr Institute

Title and abstract TBA

Title and abstract TBA

Contact Information: Prof. Philip Mannheim
More

### Condensed Matter Physics Seminar

Tuesday, October 31st, 201702:00 PM - 03:00 PM

Storrs Campus

Physics Building, P121

Dr. Jeremy Levi, University of Pittsburgh

Correlated Nanoelectronics

The study of strongly correlated electronic systems and the development of quantum transport in nanoelectronic devices

have followed distinct, mostly non-overlapping paths. Electronic correlations of complex materials lead to emergent properties such as superconductivity, magnetism, and Mott insulator phases. Nanoelectronics generally starts with far simpler materials (e.g., carbon-based or semiconductors) and derives functionality from doping and spatial confinement

to two or fewer spatial dimensions. In the last decade, these two fields have begun to overlap. The development of new growth techniques for complex oxides have enabled new families of heterostructures which can be electrostatically

gated between insulating, ferromagnetic, conducting and superconducting phases. In my own research, we use a

scanning probe to "write" and "erase" conducting nanostructures at the LaAlO3/SrTiO3 interface. The process is similar to that of an Etch-a-Sketch toy, but with a precision of two nanometers. A wide variety of nanoscale devices have already been demonstrated, including nanowires, nanoscale photodetectors, THz emitters and detectors, tunnel

junctions, diodes, field-effect transistors, single-electron transistors, superconducting nanostructures and ballistic

electron waveguides. These building blocks may form the basis for novel technologies, including a platform for

complex-oxide-based quantum computation and quantum simulation.

Correlated Nanoelectronics

The study of strongly correlated electronic systems and the development of quantum transport in nanoelectronic devices

have followed distinct, mostly non-overlapping paths. Electronic correlations of complex materials lead to emergent properties such as superconductivity, magnetism, and Mott insulator phases. Nanoelectronics generally starts with far simpler materials (e.g., carbon-based or semiconductors) and derives functionality from doping and spatial confinement

to two or fewer spatial dimensions. In the last decade, these two fields have begun to overlap. The development of new growth techniques for complex oxides have enabled new families of heterostructures which can be electrostatically

gated between insulating, ferromagnetic, conducting and superconducting phases. In my own research, we use a

scanning probe to "write" and "erase" conducting nanostructures at the LaAlO3/SrTiO3 interface. The process is similar to that of an Etch-a-Sketch toy, but with a precision of two nanometers. A wide variety of nanoscale devices have already been demonstrated, including nanowires, nanoscale photodetectors, THz emitters and detectors, tunnel

junctions, diodes, field-effect transistors, single-electron transistors, superconducting nanostructures and ballistic

electron waveguides. These building blocks may form the basis for novel technologies, including a platform for

complex-oxide-based quantum computation and quantum simulation.

Contact Information: Prof. J. Hancock
More

### UConn Physics Colloquium

Friday, November 3rd, 201703:30 PM - 04:30 PM

Storrs Campus

Physics Building, Room PB-38

Prof. Philip Mannheim, UConn

The 2017 Nobel Prize for Gravitational Waves

In 2017 the Nobel Prize in Physics was awarded to Rainer Weiss, Kip Thorne and Barry Barish for their work, along with the late Ronald Drever, in developing LIGO (the Laser Interferometer Gravitational-Wave Observatory) and then the detection of gravitational waves that had first been predicted by Albert Einstein a century earlier. The first such observation has been attributed to the collision of two black holes. We review this work and discuss the very recent observation though joint gravity wave and gamma ray detectors of the collision of two neutron stars (the so called kilonova).

Coffee will be served prior to the talk, at 3:00 p.m., In Room P-103

Please notice the new colloquium time.

The 2017 Nobel Prize for Gravitational Waves

In 2017 the Nobel Prize in Physics was awarded to Rainer Weiss, Kip Thorne and Barry Barish for their work, along with the late Ronald Drever, in developing LIGO (the Laser Interferometer Gravitational-Wave Observatory) and then the detection of gravitational waves that had first been predicted by Albert Einstein a century earlier. The first such observation has been attributed to the collision of two black holes. We review this work and discuss the very recent observation though joint gravity wave and gamma ray detectors of the collision of two neutron stars (the so called kilonova).

Coffee will be served prior to the talk, at 3:00 p.m., In Room P-103

Please notice the new colloquium time.

Contact Information: Prof. A. Puckett
More

### Atomic, Molecular, and Optical Physics Seminar

Monday, November 6th, 201704:00 PM - 05:00 PM

Storrs Campus

Physics Building, P121

Dr. George Rawitscher,

Department of Physics,

University of Connecticut

Progress in the Phase-Amplitude description of a wave function by means of a linear equation

The Phase-Amplitude (Ph-A) description consists in writing the wave function as ψ(r) = y(r) sin (φ(r)), where y is the amplitude and φ the phase. Both functions vary slowly with the distance r, and hence should be easier to calculate (especially out to large distances) than the highly oscillatory function ψ(r).

The novel approach, to be described in the talk, consists in defining u(r) = y², which obeys a linear third order differential equation. This equation is quite different from the non-linear one introduced by Milne in 1930. It is the purpose of this talk to explore the properties of the solutions of this equation, particularly in the presence of turning points.

1. A very efficient iterative solution will be described and will be applied to a repulsive Coulomb potential example. The calculations use a modern spectral expansion method. But they do not converge near a turning point.

2. A non-iterative solution method will be described. It starts from the WKB solution at large distances, but becomes unstable near a turning point.

3. By using two different numerical methods, it will be shown that the solution near turning points becomes unstable.

Department of Physics,

University of Connecticut

Progress in the Phase-Amplitude description of a wave function by means of a linear equation

The Phase-Amplitude (Ph-A) description consists in writing the wave function as ψ(r) = y(r) sin (φ(r)), where y is the amplitude and φ the phase. Both functions vary slowly with the distance r, and hence should be easier to calculate (especially out to large distances) than the highly oscillatory function ψ(r).

The novel approach, to be described in the talk, consists in defining u(r) = y², which obeys a linear third order differential equation. This equation is quite different from the non-linear one introduced by Milne in 1930. It is the purpose of this talk to explore the properties of the solutions of this equation, particularly in the presence of turning points.

1. A very efficient iterative solution will be described and will be applied to a repulsive Coulomb potential example. The calculations use a modern spectral expansion method. But they do not converge near a turning point.

2. A non-iterative solution method will be described. It starts from the WKB solution at large distances, but becomes unstable near a turning point.

3. By using two different numerical methods, it will be shown that the solution near turning points becomes unstable.

Contact Information: Prof. Phillip Gould
More

### Condensed Matter Physics Seminar

Tuesday, November 7th, 201702:00 PM - 03:00 PM

Storrs Campus

Physics Building, P121

Dr. Emil S. Bozin,

Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory

Metal-insulator transition, dimerization, and orbital degeneracy lifting in Cu Ir_2 S_4 thiospinel – a local structure tale

Transition metal chalcogenides with partially filled d-bands host some of the most amazing emergent responses including high-temperature superconductivity, colossal magnetoresistance, formation of spin-dimerized lattices, and spin and charge glass states. They often undergo structural, electronic and magnetic transitions, and display symmetry broken ground states with orders in orbital, charge and spin sectors. Most studies of these systems focus on the observed behaviors in the low temperature regime, where symmetry broken states order over long range as a product of subtle interplay of various fundamental interactions. Less is known about what happens upon heating when the long-range order melts or disappears upon doping or other excitation, yet this is possibly more crucial to understand the physics governing the properties than the much lower energy effects responsible for the ordering of the broken symmetry states. However, these are inherently difficult to study using conventional crystallographic approaches which rely on existence of long range periodicity. Probes sensitive to the presence of broken symmetry states irrespective of the status of their ordering, such as total scattering based atomic pair distribution function (PDF), are indispensable tool for revealing the nanoscale information.

Observed nematic response in copper and iron based superconductors may be one such example that has gained appreciable attention in this context recently. The high temperature regime is typically characterized by a high crystallographic symmetry structure where, due to partial filling of the d-orbitals, orbital states are degenerate and are prone to symmetry breaking to lift the degeneracy. Mechanisms of orbital degeneracy lifting (ODL) could be numerous, such as the crystal field effects, the well-known orbital-lattice Jahn-Teller effect, the superexchange interactions between the orbitals, as well as the relativistic spin-orbit coupling, and could in principle also arise from some combination of these effects. Regardless of the exact origin, studies searching for existence and exploring the character of the ODL state at high temperature, above the temperature where the broken symmetry states order (i.e., the spin or orbital ordering) are therefore of great importance as they could provide important missing ingredients instrumental for understanding the big picture.

In this talk I will present results of an X-ray PDF local structure survey of CuIr2S4 across its metal-insulator transition involving long range orbital/charge order and spin dimerization, and rationalized via orbitally-driven Peierls mechanism. The PDF study focuses on the origin of poor metallicity of the high-T metallic regime. It benefits from fort

Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory

Metal-insulator transition, dimerization, and orbital degeneracy lifting in Cu Ir_2 S_4 thiospinel – a local structure tale

Transition metal chalcogenides with partially filled d-bands host some of the most amazing emergent responses including high-temperature superconductivity, colossal magnetoresistance, formation of spin-dimerized lattices, and spin and charge glass states. They often undergo structural, electronic and magnetic transitions, and display symmetry broken ground states with orders in orbital, charge and spin sectors. Most studies of these systems focus on the observed behaviors in the low temperature regime, where symmetry broken states order over long range as a product of subtle interplay of various fundamental interactions. Less is known about what happens upon heating when the long-range order melts or disappears upon doping or other excitation, yet this is possibly more crucial to understand the physics governing the properties than the much lower energy effects responsible for the ordering of the broken symmetry states. However, these are inherently difficult to study using conventional crystallographic approaches which rely on existence of long range periodicity. Probes sensitive to the presence of broken symmetry states irrespective of the status of their ordering, such as total scattering based atomic pair distribution function (PDF), are indispensable tool for revealing the nanoscale information.

Observed nematic response in copper and iron based superconductors may be one such example that has gained appreciable attention in this context recently. The high temperature regime is typically characterized by a high crystallographic symmetry structure where, due to partial filling of the d-orbitals, orbital states are degenerate and are prone to symmetry breaking to lift the degeneracy. Mechanisms of orbital degeneracy lifting (ODL) could be numerous, such as the crystal field effects, the well-known orbital-lattice Jahn-Teller effect, the superexchange interactions between the orbitals, as well as the relativistic spin-orbit coupling, and could in principle also arise from some combination of these effects. Regardless of the exact origin, studies searching for existence and exploring the character of the ODL state at high temperature, above the temperature where the broken symmetry states order (i.e., the spin or orbital ordering) are therefore of great importance as they could provide important missing ingredients instrumental for understanding the big picture.

In this talk I will present results of an X-ray PDF local structure survey of CuIr2S4 across its metal-insulator transition involving long range orbital/charge order and spin dimerization, and rationalized via orbitally-driven Peierls mechanism. The PDF study focuses on the origin of poor metallicity of the high-T metallic regime. It benefits from fort

Contact Information: Prof. J. Hancock
More

### UConn Physics Colloquium

Friday, November 10th, 201703:30 PM - 04:30 PM

Storrs Campus

Physics Building, Room PB-38

Ken Burch, Laboratory for Assembly and Spectroscopy of Emergence, Boston College

Towards New Phases and Computer with Scotch Tape

For many years our understanding of new phases of mater relied on broken symmetries and associated new particles. Recently, there has been increasing interest in phases defined by a change in the shape of the space electrons live in. I will give an overview of this idea and how the associated new particles could be helpful in quantum computation. I will then describe our groups efforts to realize these particles in heterostructures of high Tc superconductors and

topological insulators. This includes a new method we developed for producing these interfaces with scotch tape and our recent efforts to move to realistic devices.

Coffee will be served prior to the talk, at 3:00 p.m., In Room P-121

Please notice the new colloquium time.

Towards New Phases and Computer with Scotch Tape

For many years our understanding of new phases of mater relied on broken symmetries and associated new particles. Recently, there has been increasing interest in phases defined by a change in the shape of the space electrons live in. I will give an overview of this idea and how the associated new particles could be helpful in quantum computation. I will then describe our groups efforts to realize these particles in heterostructures of high Tc superconductors and

topological insulators. This includes a new method we developed for producing these interfaces with scotch tape and our recent efforts to move to realistic devices.

Coffee will be served prior to the talk, at 3:00 p.m., In Room P-121

Please notice the new colloquium time.

Contact Information: Prof. Jason Hancock
More

### Condensed Matter Physics Seminar

Tuesday, November 14th, 201702:00 PM - 03:00 PM

Storrs Campus

Physics Building, P121

Saikat Banerjee,

Nordita,

Stockholm, Sweden

Bosonic excitations in Dirac matter

The discovery of the Dirac dispersion of electrons in graphene led to a comprehensive investigation of a list compounds and quasiparticle bands with linear band touching. A unified description of this rapidly expanding list has brought forward the term Dirac materials. The stability of the Dirac cone with respect to interactions, emergence of different phases, and transient excitonic instabilities in optically-pumped Dirac materials are, to name a few, active areas of modern condensed matter physics. Within this extensive field of research, the concept of bosonic Dirac materials has emerged. In this talk, I discuss a few realizations of Dirac materials with bosonic excitations and describe the emergence of topological bosonic surface states and their differences from their fermionic counter-parts. The effects of interactions on reshaping the bosonic Dirac cone are discussed by considering a specific case of ferromagnets consisting of Van der Waals-bonded stacks of honeycomb layers. The relevance of bosonic Dirac theory is pointed out by qualitatively enplaning an unexplained anomaly in magnetic neutron scattering data of CrBr3 from 1970. I also mention an interesting situation where the Dirac bosons have long-range coherence (form a Bose-Einstein condensate) and the difference between the dynamics of the Dirac condensate and the conventional analogue described by the Gross-Pitaevskii equation.

Nordita,

Stockholm, Sweden

Bosonic excitations in Dirac matter

The discovery of the Dirac dispersion of electrons in graphene led to a comprehensive investigation of a list compounds and quasiparticle bands with linear band touching. A unified description of this rapidly expanding list has brought forward the term Dirac materials. The stability of the Dirac cone with respect to interactions, emergence of different phases, and transient excitonic instabilities in optically-pumped Dirac materials are, to name a few, active areas of modern condensed matter physics. Within this extensive field of research, the concept of bosonic Dirac materials has emerged. In this talk, I discuss a few realizations of Dirac materials with bosonic excitations and describe the emergence of topological bosonic surface states and their differences from their fermionic counter-parts. The effects of interactions on reshaping the bosonic Dirac cone are discussed by considering a specific case of ferromagnets consisting of Van der Waals-bonded stacks of honeycomb layers. The relevance of bosonic Dirac theory is pointed out by qualitatively enplaning an unexplained anomaly in magnetic neutron scattering data of CrBr3 from 1970. I also mention an interesting situation where the Dirac bosons have long-range coherence (form a Bose-Einstein condensate) and the difference between the dynamics of the Dirac condensate and the conventional analogue described by the Gross-Pitaevskii equation.

Contact Information: Prof. J. Hancock
More

### UConn Physics Colloquium

Friday, November 17th, 201703:30 PM - 04:30 PM

Storrs Campus

Physics Building, Room PB-38

Dr. Joe Silk, Department of Physics and Astronomy, Johns Hopkins University

The Limits of Cosmology

One of our greatest challenges in cosmology is

understanding the origin of the structure of the universe, and in particular the formation of the galaxies. I will describe how the fossil radiation from the beginning of the universe, the cosmic microwave background, has provided a window for probing the initial

conditions from which structure evolved and seeded the formation of the

galaxies, and the outstanding issues that remain to be resolved. I will address our optimal choice of future strategy in order to make further progress on understanding our cosmic origins.

Coffee will be served prior to the talk, at 3:00 p.m., In Room P-103

Please notice the new colloquium time.

The Limits of Cosmology

One of our greatest challenges in cosmology is

understanding the origin of the structure of the universe, and in particular the formation of the galaxies. I will describe how the fossil radiation from the beginning of the universe, the cosmic microwave background, has provided a window for probing the initial

conditions from which structure evolved and seeded the formation of the

galaxies, and the outstanding issues that remain to be resolved. I will address our optimal choice of future strategy in order to make further progress on understanding our cosmic origins.

Coffee will be served prior to the talk, at 3:00 p.m., In Room P-103

Please notice the new colloquium time.

Contact Information: Prof. Philip Mannheim
More

### Condensed Matter Physics Seminar

Tuesday, November 28th, 201702:00 PM - 03:00 PM

Storrs Campus

Physics Building, P121

A. Kussow, UMass Lowell

Title: TBA

Title: TBA

Contact Information: Prof. J. Hancock
More

### Open Lecture on Diversity and Inclusion

Tuesday, November 28th, 201703:30 PM - 04:30 PM

Storrs Campus

Biophysics Room 131

Solving the complex problems that we face in our world today requires a more talented workforce

than we have ever needed before. Such a workforce must be comprised of a wide range of diverse

talents and creative insights. No segment of the population can be ignored or overlooked in this

talent search. This presentation will describe the most recent research that demonstrates the

positive impact that social and informational diversity has on science and scholarly advancement,

the reasons for this impact and the importance of committed leadership in achieving a strong,

supportive and inclusive workplace where creativity and productivity is maximized.

than we have ever needed before. Such a workforce must be comprised of a wide range of diverse

talents and creative insights. No segment of the population can be ignored or overlooked in this

talent search. This presentation will describe the most recent research that demonstrates the

positive impact that social and informational diversity has on science and scholarly advancement,

the reasons for this impact and the importance of committed leadership in achieving a strong,

supportive and inclusive workplace where creativity and productivity is maximized.

Contact Information: caroline.cichocki@uconn.edu
More

### Astronomy Seminar Series

Wednesday, November 29th, 201702:00 PM - 03:00 PM

Storrs Campus

P121

Anna Pancoast, TBA

Contact Information: Prof. Whitaker
More

### Charles Reynolds Distinguished Lecture Series

Friday, December 1st, 201703:30 PM - 04:30 PM

Storrs Campus

Physics Building, Room PB-38

Suchitra Sebastian, Cambridge University, United Kingdom

Exploring Materials Universes

Materials comprise trillions of electrons that interact with each other to create a diversity of physical behaviours. We owe much of modern technology - from powerful computing to the marvels of communication - to discoveries of new types of collective electron behaviours in materials. Such discoveries, however, are often serendipitous, given that materials can be thought of as complex universes teeming with vast numbers of electrons, making their behaviours challenging to understand or predict. A question we are often confronted with is how to make progress in discovering novel collective electron behaviours akin to new universes. I will discuss possible approaches to increasing the odds of making discoveries, with examples from cases such as new superconductors and new types of dual metal-insulating materials.

Coffee will be served prior to the talk, at 2:30 p.m., In Room P-103

Please notice the new colloquium time.

Exploring Materials Universes

Materials comprise trillions of electrons that interact with each other to create a diversity of physical behaviours. We owe much of modern technology - from powerful computing to the marvels of communication - to discoveries of new types of collective electron behaviours in materials. Such discoveries, however, are often serendipitous, given that materials can be thought of as complex universes teeming with vast numbers of electrons, making their behaviours challenging to understand or predict. A question we are often confronted with is how to make progress in discovering novel collective electron behaviours akin to new universes. I will discuss possible approaches to increasing the odds of making discoveries, with examples from cases such as new superconductors and new types of dual metal-insulating materials.

Coffee will be served prior to the talk, at 2:30 p.m., In Room P-103

Please notice the new colloquium time.

Contact Information: Prof. Jason Hancock
More