Victor Gurarie

Gurarie

kdcadmin — Wed, 15 Mar 2023 17:30:06 +0000

Victor Gurarie

Affiliations

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

Bio

I am interested in emergent phenomena in condensed matter and many body physics, when the behavior of many-body systems cannot be reduced to a sum of their constituent parts. Common methods used in my work are the nonperturbative techniques of many-body theory and quantum field theory. My work has applications within the new field of the ultracold atomic gases, in the more conventional condensed matter physics, as well as to the mathematical aspects of quantum field theory.

CTQM Role

CTQM Fellow

Research Category

condensed matter physics

victor.gurarie@colorado.edu

Phone

303-735-5898 (office)

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

Exciting Adventures in Coupling

kdcadmin — Fri, 26 Sep 2014 17:31:27 +0000

Exciting Adventures in Coupling kdcadmin Fri, 09/26/2014 - 11:31 am

According to new theory by the Gurarie and Rey groups, dipole-dipole interactions between ultracold polar molecules pinned in an optical lattice can make the molecules swap their internal rotational state (spin) at the cost of inducing a net spin current across the lattice. This elaborate spin swapping, which affects molecule motion or circulation, is known as spin-orbit coupling.

Image Credit

The Rey group and Steve Burrows

New theory describing the spin behavior of ultracold polar molecules is opening the door to explorations of exciting, new physics. According to the Gurarie and Rey theory groups, ultracold dipolar molecules can do even more interesting things than swapping spins. For instance, spin swapping occurs naturally when ultracold potassium-rubidium (KRb) molecules are in two of their four possible excited and ground states. The differences in two states are sufficient to cause a spinning molecule to slow down at the same time another molecule begins to rotate.

The exciting news is that when two KRb molecules are in three of the four possible states, they don’t just swap their spins. The direction of the spin in the molecule that starts rotating gets reversed! This more elaborate spin swapping affects the motion of the molecules, a phenomenon known as spin-orbit coupling.

Spin-orbit coupling is something that happens in solids when electrons move inside the electric field of a crystal. This process is the key to understanding spin transport and spin currents, which are analogs of electron transport and electric currents. Spin-orbit coupling also plays a role in some very exotic phenomena such as the creation of a Majorana particle, which is its own antiparticle!

The theorists responsible for discovering these exciting new adventures in spin-orbit coupling are research associates Sergey Syzranov and Michael Wall, CU Associate Professor of Physics Victor Gurarie, and CU Associate Research Professor of Physics Ana Maria Rey. Guarie and Rey are CTQM Fellows. Their discovery of spin-orbit coupling in ultracold molecules was reported online in Nature Communications on November 7, 2014.

The next step in this research is finding a model system for learning how to implement and control spin-orbit coupling. And, ultracold polar-molecule experiments are ideally suited for this purpose. For example, ultracold KRb molecules are polar, which means that the K end of one molecule attracts the Rb end of another molecule, while two K ends or two Rb ends repel each other. These behaviors are known as dipole-dipole interactions. The new theory predicts that dipole-dipole interactions will spontaneously give rise to spin-orbit coupling in an ultracold gas of polar molecules.

“The nice part is that with cold molecules, spin-orbit coupling just exists,” Rey explained. “We don’t need to zap anything with a laser to create it.”

Rey and her collaborators predict that spin-orbit coupling in ultracold polar molecules will generate excitations called chirons. Chirons are similar to the quasi particles found in bilayer graphene. They are expected to show up in the spin behaviors, spin currents, and spin interactions that occur in an ensemble of ultracold polar molecules pinned inside a deep optical lattice (a crystal of light created by intersecting laser beams). In other words, just about everything predicted by the new theory could soon be tested in the ultracold molecule laboratory in JILA!

Principal Investigators

Ana Maria Rey

Victor Gurarie

Research Topics

atomic, molecular, and optical physics