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Condensed Matter Seminars This Term

ics Condensed Matter
Thursday, May 16, 2019
11:00 AM
Physics Building, Room 313
Professor Ying-Jer Kao [Host: Gia-Wei Chern]
National Taiwan University
"Tunneling-induced restoration of classical degeneracy in quantum kagome ice"
ABSTRACT:

Quantum effect is expected to dictate the behavior of physical systems at low temperature. For quantum magnets with geometrical frustration, quantum fluctuation usually lifts the macroscopic classical degeneracy, and exotic quantum states emerge. However, how different types of quantum processes entangle wave functions in a constrained Hilbert space is not well understood. Here, we study the topological entanglement entropy (TEE) and the thermal entropy of a quantum ice model on a geometrically frustrated kagome lattice. We find that the system does not show a Z2 topological order down to extremely low temperature, yet continues to behave like a classical kagome ice with finite residual entropy. Our theoretical analysis indicates an intricate competition of off-diagonal and diagonal quantum processes leading to the quasi-degeneracy of states and effectively, the classical degeneracy is restored.

ics Condensed Matter
Tuesday, May 28, 2019
11:00 AM
Physics Building, Room 313
Note special date.
Joseph Avron [Host: Israel Klich ]
Technion
"Flexible Sganac interferometers for the neophytes"
ABSTRACT:

I shall review the history of Sagnac interferometers and give a geometric description of light rays propagation in flexible optical fibers in Minkowski space. Based on joint works with Amos Ori and Oded Kenneth.

ics Condensed Matter
Thursday, May 30, 2019
11:00 AM
Physics Building, Room 313
Adam Wei Tsen [Host: Seunghun Lee]
University of Waterloo
"Two-dimensional magnetism and spintronics"
ABSTRACT:

The recent discoveries of ferromagnetism in single atomic layers have opened a new avenue for two-dimensional (2D) materials research. Not only do they raise fundamental questions regarding the requirements for long-range magnetic order in low-dimensional systems, but they also provide a new platform for the development of spintronic devices. In this talk, I will present a series of studies on the family of layered ferromagnetic semiconductors, CrX3 (X = I, Br, Cl), in the atomically thin limit. By incorporating these materials as tunnel barriers between graphene electrodes, we are able to achieve extremely large tunnel magnetoresistance as well as robust memritive switching that is tunable with magnetic field. Tunneling spectroscopy further allows for direct observation of their spin wave excitations, or magnons, from which we are able to derive a simple microscopic Hamiltonian for all three spin systems. These results show that strong exchange anisotropy is not necessary to stabilize ferromagnetism in the monolayer limit.

Condensed Matter Seminars
Jeffrey Teo (Chair)

To add a speaker, send an email to ct5wa@Virginia.EDU Include the seminar type (e.g. Condensed Matter Seminars), date, name of the speaker, title of talk, and an abstract (if available). [Please send a copy of the email to phys-speakers@Virginia.EDU.]