# Dmitry Kovrizhin

Dr Dmitry Kovrizhin

EPSRC Advanced Research Fellow

Office: 518 Mott Bld

Phone: +44(0)1223 3 39582

Email: dk487 @ cam.ac.uk

Personal web site

TCM Group, Cavendish Laboratory

19 JJ Thomson Avenue,

Cambridge, CB3 0HE UK.

Research Group

## Research

I am a condensed matter theorist. My research is about physical phenomena which arise as a result of a collective behaviour of many interacting quantum particles. One of the main areas of my work is the field of non-equilibrium quantum systems, where I studied e.g. electronic interferometers, and thermalisation of electrons in quantum Hall edge states. I have also developed theoretical methods of "non-equilibrium bosonization". More recently I have been working on non-equilibrium dynamics of quantum spin-liquids, where I calculated the spin dynamic structure factor of the Kitaev model. Below is the list of my current research interests.

- non-equilibrium quantum systems
- frustrated magnetism, quantum spin liquids
- topological phases
- topological defects and textures

## In Plain English

**Non-equilibrium quantum systems:** The occurrence of
non-equilibrium behaviour is very common in nature. One of the simplest
examples of that is when two objects with different temperatures come
into contact. Other non-equilibrium settings can show various levels of
complexity from the physical process that leads to emission of a laser to
the ultimate case of living organisms. The common characteristic property
of these systems is the absence of uniform thermodynamic quantities such
as temperature.

Some of the non-equilibrium experiments are being done with
nano-structures in high magnetic fields and at very low temperatures. In
these systems electrons move in a coherent way similar to photons in a
laser beam. Remarkably, as a result of strong interactions the electrons
form emergent **correlated states** which harbour quasi-particles
with a fraction of electron charge. Similar quasi-particles also occur
in magnetic materials in the so-called **quantum spin liquid**
states. In the future it is hoped that these particles will be used
as building blocks of topological quantum computers. The problem of
quantum motion of a large collection of quasi-particles is in the class
of non-equilibrium quantum problems, whose study constitutes one of the
main areas of my research.

Interestingly, many of these systems show **non-equilibrium steady
states**. Take a piece of metal and connect it on opposite sides to a
heater and a refrigerator, — which will result in a steady heat flow. A
similar situation occurs in a system of interacting electrons in a quantum
wire connected to a battery. The important differences with the former
arises from the fact that the motion of particles in the wire obeys the
laws of quantum mechanics, which lead to unusual quantum states. Recently
it became possible to study these states in experiments, which resulted
in a number of unexpected observations. Next generation experiments will
build quantum devices, which iwill explore the physics of non-equilibrium
states, based on new theoretical and experimental insights.

My research is aimed at theoretical understanding of quantum systems
driven **far from equilibrium** by, for example, applied voltage
or fast switching of external fields. In these settings many physical
systems with examples ranging from semiconductor nano-structures
and superconductors, to quantum magnets and ultra-cold atomic gases
show remarkable **emergent behaviour**. This comes as a result of
an intricate quantum entanglement which occurs due to the motion of
interacting particles under non-equilibrium conditions. The properties of
these systems cannot be explained using standard theoretical framework,
and it is the one of the central tasks of my work to develop this
theoretical description.

## Featured Publications

* complete list of publications is available here, my papers can also be found on arXiv

**Dynamics of a Two-Dimensional Quantum Spin Liquid: Signatures of
Emergent Majorana Fermions and Fluxes**
J. Knolle, D. L. Kovrizhin, J. T. Chalker, and R. Moessner
Phys. Rev. Lett. **112**, 207203, (2014) [PRL,
arXiv:1308.4336]
see physics viewpoint by Alexei Tsvelik Quasiparticle Signatures
in Quantum Spin Liquids

**Bulk-edge correspondence in fractional Chern insulators**
Zhao Liu, D. L. Kovrizhin, and Emil J. Bergholtz
Phys. Rev. B **88**, 081106(R), (2013) [PRB
(Rapid Comm), arXiv:1304.1323]

**Multicomponent Skyrmion Lattices and Their Excitations**
D. L. Kovrizhin, Benoît Douçot, and R. Moessner
Phys. Rev. Lett. **110**, 186802 (2013) [PRL,
arXiv:1207.4021]

**Relaxation in Driven Integer Quantum Hall Edge States**
D. L. Kovrizhin and J. T. Chalker
Phys. Rev. Lett. **109**, 106403 (2012) [PRL,
arXiv:1111.3914]

**Exactly solved model for an electronic Mach-Zehnder
interferometer**
D. L. Kovrizhin and J. T. Chalker
Phys. Rev. B **80**, 161306(R) (2009) [PRB
(Rapid Comm) , arXiv:0903.3387]

**Density matrix renormalization group for bosonic quantum Hall
effect**
D. L. Kovrizhin
Phys. Rev. B **81**, 125130 (2010) [PRB,
arXiv:0909.3693]

**Bose-Einstein Condensation of Magnons in Cs2CuCl4**
T. Radu, H. Wilhelm, V. Yushankhai, D. Kovrizhin, R. Coldea,
Z. Tylczynski, T. Lühmann, and F. Steglich
Phys. Rev. Lett. **95**, 127202 (2005) [PRL,
cond-mat/0505058]
also advertised in "First Bose-Einstein Condensate in a Solid", Physics
News Update 746 2 (2005)

**Anomalous Tunneling of Phonon Excitations between Two Bose-Einstein
Condensates**
Yu. Kagan, D. L. Kovrizhin, and L. A. Maksimov
Phys. Rev. Lett. **90**, 130402 (2003) [PRL,
cond-mat/0210329]