Leo Radzihovsky

Radzihovsky

kdcadmin — Thu, 23 Mar 2023 18:21:14 +0000

Leo Radzihovsky

Affiliations

Fellow of CTQM
Professor, Department of Physics, University of Colorado Boulder

Bio

My research interests are:

Degenerate Atomic Gases
Liquid Crystals and Other 'Soft' Condensed Matter
Disordered Systems
Nonequilibrium Phenomena
Quantum Hall Effect
Superconductivity

For more details, please see my Physics Department homepage.

CTQM Role

CTQM Fellow

Research Category

condensed matter physics

radzihov@colorado.edu

Phone

303-492-5436 (office)

303-492-2998 (fax)

Website

http://spot.colorado.edu/~radzihov/

Condensed Matter Physics

kdcadmin — Thu, 09 Mar 2023 21:42:11 +0000

Condensed Matter Physics kdcadmin Thu, 03/09/2023 - 2:42 pm

The field of condensed matter physics explores the macroscopic and microscopic properties of matter. Condensed Matter physicists study how matter arises from a large number of interacting atoms and electrons, and what physical properties it has as a result of these interactions.

Traditionally, condensed matter physics is split into "hard" condensed matter physics, which studies quantum properties of matter, and "soft" condensed matter physics which studies those properties of matter for which quantum mechanics plays no role.

The condensed matter field is considered one of the largest and most versatile sub-fields of study in physics, primarily due to the diversity of topics and phenomena that are available to study. Breakthroughs in the field of condensed matter physics have led to the discovery and use of liquid crystals, modern plastic and composite materials and the discovery of the Bose-Einstein Condensate.

CTQM Fellow(s)

Law and Disorder

kdcadmin — Mon, 06 Apr 2015 17:41:24 +0000

Law and Disorder kdcadmin Mon, 04/06/2015 - 11:41 am

As disorder increases (l–r) in Weyl semimetal, a threshold is reached where a transition occurs between a quantum phase in which electrons get more localized and stop moving and a quantum phase with less disorder in which the electrons never become localized and Weyl semimetal acts like a conductor on steroids. Remarkably, the two quantum phases can transition back and forth from one to the other.

Image Credit

The Center for Theory of Quantum Matter and Steve Burrows

In everyday life, conductors are materials that conduct electricity. These materials are used to make metallic wires that carry electricity into our homes. In contrast, insulators, which don’t conduct electricity, surround these wires in our plugs so we don’t get electrocuted plugging in our computers, appliances, and lights. The difference between a conductor and an insulator is often the amount of disorder, or impurities, present in an electronic material. If such disorder exceeds a certain threshold, the impurities can actually stop electron flow and turn a conductor into an insulator, all because of a phenomenon known as localization.

Localization traps electrons in place and prevents them from moving through a material. Showing exactly how localization works requires the complex mathematics of quantum mechanics. Since quantum mechanics leads to all sorts of wild and crazy things, CTQM Junior Fellow Sergey Syzranov and CTQM Fellows Victor Gurarie and Leo Radzihovsky decided to investigate localization in higher dimensions. The wonderful thing about being theorists is that they didn’t consider stopping at three dimensions either.

The three theorists discovered something quite interesting happens in sufficiently high dimensions: Depending on whether or not the disorder exceeds a certain threshold, all conductors will be in one of two distinct quantum phases. In the more disordered phase as the disorder increases, more and more electrons become localized and stop moving—much like they would in our ordinary three-dimensional world. Electrons in this state behave pretty much like they do in conventional conductors.

However, the second phase with less disorder has characteristics that were totally unexpected. In this phase, even when the disorder is added (although not beyond the threshold), the electrons never become localized. As a result, electronic materials in this quantum state behave like conductors on steroids. Even resistance due to impurities doesn’t stop the flow of electrons inside them.

What’s even more curious is that near the disorder threshold, the two quantum phases can transition back and forth from one to the other. Such a quantum phase transition is quite remarkable because electronic materials are complicated, and the two phases are very different.

In the process of learning more about this remarkable quantum phase transition, the theorists realized there may be a way to observe such a transition in a real material such as Weyl semimetal. Weyl semimetal is a three-dimensional analog of graphene. According to the new theory, the quantum phase transition will occur in three dimensions in this unique material, opening the door to observing it in the laboratory!

Right now, it’s impossible to predict the impact of this important discovery on the future of electronics. Theorists often open up new frontiers in science, typically without realizing what those frontiers will look like. For example, when Heinrich Hertz, discoverer of electromagnetic waves, was asked about the ramifications of his discovery, he replied, “Nothing, I guess.” Nothing has turned out to be radio, television, and cell phones, to name a few devices in widespread use today.

Principal Investigators

Leo Radzihovsky

Victor Gurarie

Research Topics

condensed matter physics

Magic Atom Theory

kdcadmin — Mon, 08 Dec 2014 18:34:30 +0000

Magic Atom Theory kdcadmin Mon, 12/08/2014 - 11:34 am

Quantum mechanical theory developed by CTQM Fellow Leo Radzihovsky and CU graduate student Xiao Yin provides a detailed description the quantum state of a strongly interacting and highly nonequilibrium BEC created by the Cornell and Jin groups.

Image Credit

Steve Burrows and Brad Baxley

In 2013, the Cornell and Jin groups created and studied an extremely strongly interacting Bose-Einstein condensate (BEC) of rubidium atoms (⁸⁵Rb). This BEC was short lived and far out of equilibrium. At the time the experimentalists wondered if this new BEC could be a quantum liquid because the quantum mechanical waves of these puffed-up atoms were rubbing up against each other and sliding past one another—like atoms do in liquids we are familiar with in everyday life.

This seminal experiment captured the attention of CU Physics Professor and CTQM Fellow Leo Radzihovsky, who had been developing a theory of ⁸⁵Rb for many years. Not surprisingly, Radzihovsky wanted to further develop the theory to explain what was really going on with the puffy ⁸⁵Rb atoms in the new experiment. Radzihovsky and CU graduate student Xiao Yin discovered that the quantum state (phase) of the strongly interacting atoms was much wilder and crazier than anyone expected.

The quantum state of the strongly interacting BEC was neither a gas nor a liquid. Rather, it was something altogether new that had properties of both. The ability of a strongly interacting gas of ⁸⁵Rb atoms to be both a gas and a liquid at the same time is purely quantum mechanical and has no analog in ordinary life.

An even more significant accomplishment was that the new theory explained why a strongly interacting BEC behaves they way it does. For example, it confirmed the experimental observation of the evolution of strongly interacting ⁸⁵Rb atoms into a non-equilibrium steady state. It also described specific characteristics of the strongly interacting BEC such as the distribution of its momentum (including its long tail). And, the theorists were recently able to identify the Contact via an analysis of this momentum distribution. Although the Contact was predicted to appear in ultracold gases under conditions when the atoms are close “contact” in a BEC, it has not been observed in the Cornell-Jin experiment.

Radzihovsky and Yin recently completed additional work on strongly interacting BECs, including an analysis of the RF spectroscopy used in the experiment and a deeper look into the behavior of the system (e.g., its excitation energy) as it evolves. In the future, they plan to continue to study the evolution of the strongly interacting BEC system from the time it is created until the BEC disappears as the ⁸⁵Rb atoms form molecules.

Principal Investigators

Leo Radzihovsky

Research Topics

atomic, molecular, and optical physics