College of Arts and Sciences

TBA

Host: Harsh Mathur

Continue reading… Postponed: Aashish Clerk , University of Chicago

TBA

Host: Lydia Kisley

Continue reading… Sveta Morozova, Department of Macromolecular Science and Engineering, Case Western Reserve University

Complex magnetic excitations in a honeycomb ferromagnet CrI3
Liuyan Zhao, Department of Physics, University of Michigan, Ann Arbor

Two-dimensional (2D) honeycomb ferromagnetic monolayers are predicted to host massless Dirac magnons because of the two equivalent magnetic sites per unit cell of the honeycomb lattice, mimicking Dirac electrons in graphene. More interestingly, the introduction of the next-nearest-neighbor Dzyaloshinskii-Moriya interaction breaks the sublattice equivalency and suggests the emergence of topological magnons in these honeycomb ferromagnets. Recenly, CrI3, a honeycomb ferromagnet, has attracked tremendous attention because of the long-range 2D ferromagnetic order in its monolayer, the interlayer antiferromagnetic order in its few layers,

Continue reading… CANCELLED until later notice: Prof. Liuyan Zhao, University of Michigan,Ann Arbor, Complex magnetic excitations in a honeycomb ferromagnet CrI3

Field theory of a hexagonal antiferromagnet with 3 sublattices

Sayak Dasgupta, John’s Hopkins University, Department of Physics

We present a classical field theory of magnetization dynamics in a generic 3-sublattice antiferromagnet in 2 spatial dimensions exemplified by the Heisenberg model on the triangular [1] and kagome [2] lattices. In a ground state, spins from the 3 sublattices are coplanar and at angles of 120° to one another such that S1+S2+S3=0. The six normal modes, shown in Fig. 1, either keep the spins in this plane (the a modes) or take them out of the plane (the b modes).

Continue reading… CANCELLED or postponed: Sayak Dasgupta, Johns Hopkins University, Field theory of a hexagonal antiferromagnet with 3 sublattices

Continue reading… Spring break, no seminar

Continue reading… APS March Meeting, No seminar

List of speakers: not necessarily in that order, Please note earlier start at 12:30 pm and end at 2:00 pm

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Kyle Crowley, Electrical Transport in Chemically Exfoliated LixCoO2 in 2D Nanoflake Form

Brian Holler, 2D Semiconductor Transistors using Layered van der Waals Oxide MoO3 as High-K Gate Dielectric

Arvind Shankar Kumar, Negative Parabolic Magneto-resistance in a strongly interacting 2D Hole system in GaAs/AlGaAs

Mahdi Mehrnia, Fast, low-power defect-induced polarity switching of a magnetic vortex core

Ruihao Li, Nonlinear Planar Hall as Another Signature of Chiral Anomaly in Weyl Semimetals

Amol Ratnaparkhe,

Continue reading… CWRU Physics grad students, APS March meeting talks preview

Microwave amplification at the quantum limit: implementing and operating a Josephson parametric amplifier

A microwave electromagnetic field cooled down to millikelvin temperatures can reach its ground state: at this stage, all thermal fluctuations are suppressed and only quantum fluctuations remain. Reaching this regime enabled manipulation of the microwave fields at the single-photon level but also required the development of ultra-low-noise microwave amplifiers to ensure the detection of these quantum microwave states. Relying on non-dissipative parametric amplification using Josephson junctions, these Josephson parametric amplifiers (JPA) perform amplification while adding as little noise as allowed by quantum mechanics.

Continue reading… Audrey Bienfait (ENS-Lyon) Michelson Postdoctoral Prize Lecture

Magnetic resonance with quantum microwaves

In usual magnetic resonance experiments, the coupling between spins and their electromagnetic environment is quite weak, severely limiting the sensitivity of the measurements and any interaction at the quantum level between spins and microwaves. In this lecture, I will show that using a Josephson parametric microwave amplifier combined with high-quality factor superconducting micro-resonators cooled at millikelvin temperatures enable the implementation of a magnetic resonance spectrometer where the detection sensitivity is limited by quantum fluctuations of the electromagnetic field instead of thermal or technical noise. The small mode volume superconducting microwave resonator also enhances the spin-resonator coupling up to the point where quantum fluctuations have an effect on the spin dynamics: The spin spontaneous emission of microwave photons in the resonator is dramatically enhanced by the Purcell effect,

Continue reading… Audrey Bienfait (ENS-Lyon) Michelson Postdoctoral Prize Lecture

Phonon-mediated quantum state transfer and remote entanglement

Heavily used in classical signal processing, surface acoustic waves (SAWs) have also been proposed as a means to coherently couple distant solid-state quantum systems. Several groups have already reported the coherent coupling of standing SAWs modes to superconducting qubits, opening the door to the control and detection of quantum phonon states. In this lecture, I will explore the coherent coupling of superconducting qubits to propagating SAWs, demonstrating that quantum state transfer as well as remote entanglement generation between superconducting qubits using propagating SAWs can be realized.

Continue reading… Audrey Bienfait, (ENS-Lyon) Michelson Postdoctoral Prize Lecture

Computational Photochemistry: Onwards with first-principles

Shane Parker, Department of Chemistry, Case Western Reserve University

Photochemistry lies at the heart of chemical, biological, and technological processes, from photosynthesis to solar electricity generation. To harness the potential of light to drive new chemistry, a detailed understanding of the mechanisms of photochemical reactions is necessary. However, this is difficult to impossible to achieve based on experimental observations alone (often spectroscopy). I will introduce nonadiabatic molecular dynamics (NAMD) simulations using time-dependent density functional theory (TDDFT), an increasingly important framework that can unravel the atomistic details of photochemical reactivities.

Continue reading… Shane Parker, Dept. of Chemistry, Computational Photochemistry: Onwards with first-principles

Title: Signatures of topological ground state degeneracy in Majorana islands

Abstract:

We consider a mesoscopic superconducting island hosting multiple pairs of Majorana zero-energy modes. The Majorana island consists of multiple p-wave wires connected together by a trivial (s-wave) superconducting backbone and is characterized by an overall charging energy $E_C$; the wires are coupled to normal-metal leads via tunnel junctions. Using a combination of analytical and numerical techniques we calculate the average charge on the island as well as non-local conductance matrix as a function of a p-wave pairing gap $\Delta_P$, charging energy $E_C$ and dimensionless junction conductances $g_i$.

Continue reading… Jukka Vayrynen, Microsoft Station Q, Santa Barbara , Signatures of topological ground state degeneracy in Majorana islands

Continue reading… MLK Jr holiday, no seminar