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 Egor
Babaevemails: babaev "at" kth "dot" se egorbabaev "at" gmail "dot" com Skype: jsb1080 phone + 46 (0)735737349 In February you can reach me at phone +1 413 -2417129 Image on the right: Hopf fibration
by Ken Snoemake
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| News:
2010 Tage Erlander prize in physics awarded by the Royal Swedish
Academy of Science "for groundbreaking theoretical work that predicts
new states of matter in the form of quantum fluids with novel properties" |
| Observation
of "Type-1.5
superconductivity" is reported by
Victor Moshchalkov's group: Standard textbook classification of superconductors divides all the materials in two classes type-I and type-II depending on their rection to magnetic field. The distinctive feature of type-II class is that it can respond to applied magnetic field by forming quantum vortices. These vortices repel each other and thus tend to form order structures: vortex lattices. In two my papers from 2003 and 2005 with Martin Speight http://arxiv.org/abs/cond-mat/041168 http://arxiv.org/abs/cond-mat/0302218 it was predicted that this dichotomy is broken in multicomponent superconductors where we found an entirely new type of thermodybnamically stable vortex solutions which have attractive interaction at long range and repulsive at short range. In the recent experiment by Victor Moshchalkov's group the authors observed coexistence of vortex droplets and Meissner domains in Magnesium Diboride strikingly similar to the predicted by us picture of the "semi-Messiner state". Victor Moshchalkov and collaborators coined for it the name "type-1.5 superconductivity". See also a news story in Science Magazine "New Type of Superconductivity Spotted" and a feature at PhysicsWeb "Type-1.5 superconductor shows its stripes" Our new theoretical work on this topic: E. Babaev J. Carlstrom, M. Speight "Type-1.5 superconductivity from interband Josephson coupling" |
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Recent
Research topics: "Super"-states of matter, such as superconductivity and superfluidity have attracted interest for almost a century. Four aggregate “super” states of matter are presently known: (i) superconducting electrons in metals, (ii) superfluid liquid He, (iii) superfluid vapours of ultracold atoms in traps, (iv) and possibly supersolid state of He. These experimental discoveries resulted into a breakthrough in our insight into the laws of microworld and even had impact well beyond condensed matter physics influencing e.g. the first discussions of the Higgs effect, chiral symmetry breakdown in QCD etc. A question to rise today is where the next experimental breakthrough in the field of quantum fluids might yet arise and whether the classification of quantum fluids into the above four classes can be extended: main focus of my recent research (see links to recent papers below) was on hydrogen which, I proposed that hydrogen at ultra high compression may form two band new types of “super” state of matter - the metallic superfluid and the superconducting superfluid. The pressures where this state is expected to form are extremely high but experimentally accessible: the required pressure is around four millions athmospheres while pressures exceeding three millions athmospheres have already been achieved in laboratories and most recent experiments aim at achieving pressures in the range of 10 millions athmospheres in not so distant future. Background image: snapshot from Monte-Carlo simulations of vortex matter in the projected liquid metallic state of hydrogen (credit: Smiseth and Smorgrav) |
| For popular description see
e.g. the following media coverage in different
languages of our recent papers Swedish
"Nya teorier om metalliska supervätskor ger kvantfysiken nytt blod" English: Physics World "Back to Square one for Superfluidity, PhysicsWeb "Metallic superfluid seen in computer" Nature Physics Research Highlight "Known unknowns in high-pressure hydrogen" Russian: link French link German link, Spanish link, Dutch link, Farsi link , Norwegian link, Korean link |
| Talks of the Quantum Fluids 2007 workshop which I was organizing are now online http://www.nordita.org/~qf2007 |
| Vita: I find many kinds of things interesting. my main interests are: 1) Physics 2) Renaissanse music and especially music by J.S. Bach 3) Marathon running and weightlifting 4)I also have considerable interst in history |
| Science
(briefly): Selected publications: (see also full list of publications) My papers at LANL My papers at SLAC SPIRES Egor Babaev "Non-Meissner electrodynamics and knotted solitons in two-component superconductors" arXiv:0809.4468 Phys. Rev. B 79, 104506 (2009) Egor Babaev A possible mechanism of effective decoupling of hadronic superfluids in precessing neutron star arXiv:0901.4380 Egor Babaev, N. W. Ashcroft (Nature Physics 3, 530 - 533 (2007) "Violation of Onsager-Feynman quantization and the London Law in multicomponent superconductors" Two quite fundamental principles governing the response to rotation of ordinary superfluids and superconductors, the Onsager-Feynman quantization of superfluid velocity [1, 2], and the London law [3] relating the angular velocity to a sub sequently established magnetic field, are shown to be violated in a two-component superconductor. The manifestation of the two principles normally involves the fundamental constants alone, but this no longer holds as is demonstrated explicitly for the projected liquidmetallic states of hydrogen, and deuterium at high pressures. The rotational responses of liquid metallic hydrogen or deuterium identify them as a new class of dissipationless states; they also directly point to a particular experimental route for verification of their existence. Egor Babaev, A. Sudbo, N. W. Ashcroft (Nature 431, 666 (2004)) "A superconductor to superfluid phase transition in liquid metallic hydrogen " Although hydrogen is the simplest of atoms, it does not form the simplest of solids or liquids. Quantum effects in these phases are considerable (a consequence of the light proton mass) and they have a demonstrable and often puzzling influence on many physical properties, including spatial order. To date, the structure of dense hydrogen remains experimentally elusive. Recent studies of the melting curve of hydrogen indicate that at high (but experimentally accessible) pressures, compressed hydrogen will adopt a liquid state, even at low temperatures. In reaching this phase, hydrogen is also projected to pass through an insulator-to-metal transition. This raises the possibility of new state of matter: a near ground-state liquid metal, and its ordered states in the quantum domain. Ordered quantum fluids are traditionally categorized as superconductors or superfluids; these respective systems feature dissipationless electrical currents or mass flow. Here we report a topological analysis of the projected phase of liquid metallic hydrogen, finding that it may represent a new type of ordered quantum fluid. Specifically, we show that liquid metallic hydrogen cannot be categorized exclusively as a superconductor or superfluid. We predict that, in the presence of a magnetic field, liquid metallic hydrogen will exhibit several phase transitions to ordered states, ranging from superconductors to superfluids click here to see the cover page of 7th Oct Nature issue click here to see the an article on it in Physics World Research highlight in the first issue of Nature Physics describing my recent PRL paper Article on our recent research on this topic in PhysicsWeb.org Egor Babaev, Ludvig D. Faddeev and Antti J. Niemi cond-mat/0106152 Phys. Rev. B 65, 100512(R) (2002) "Hidden symmetry and knot solitons in a charged two-condensate Bose system" We show that a charged two-condensate Ginzburg-Landau model or equivalently a Gross-Pitaevskii functional for two charged Bose condensates, can be mapped onto a version of the nonlinear O(3) $\sigma$-model. This implies in particular that such a system possesses a hidden $O(3)$ symmetry that allows for the formation of stable knotted solitons. (For some links on knotted solitons follow this link ) Fetch citation of this paper in field-theoretic literature (from SPIRES) Egor Babaev cond-mat/0111192 Phys. Rev. Lett. 89, 067001 (2002) "Vortices with Fractional Flux in Two-Gap Superconductors and in Extended Faddeev Model" We discuss linear topological defects allowed in two-gap superconductors and equivalent extended Faddeev model. We show that, in these systems, there exist vortices which carry an arbitrary fraction of magnetic flux quantum. Besides that, we discuss topological defects which do not carry magnetic flux and describe features of ordinary one-magnetic-flux-quantum vortices in the two-gap system. The results could be relevant for the newly discovered two-band superconductor MgB2 Eivind Smorgrav, Egor Babaev, Jo Smiseth, Asle Sudbo (cond-mat/0508286) Phys. Rev. Lett. 95, 135301 (2005) "Observation of a metallic superfluid in a numerical experiment" We report the observation, in Monte Carlo simulations, of a novel type of quantum ordered state: {\it the metallic superfluid}. The metallic superfluid features ohmic resistance to counter-flows of protons and electrons, while featuring dissipationless co-flows of electrons and protons. One of the candidates for a physical realization of this remarkable state of matter is hydrogen or its isotopes under high compression. This adds another potential candidate to the presently known quantum dissipationless states, namely superconductors, superfluid liquids and vapours, and supersolids. E. Babaev (hep-th/9909052) (Int. J. Mod. Phys A 16 1175 (2001). "Nonlinear sigma model approach for phase disorder transitions in chiral Gross-Neveu, Nambu-Jona-Lasinio models and strong-coupling superconductors " Fetch citation of this paper in field-theoretic literature (from SPIRES) Egor Babaev and J. Martin Speight cond-mat/0411681 Phys. Rev. B in print "Thermodynamically stable non-local vortices, vortex molecules and semi-Meissner state in neither type-I nor type-II multicomponent superconductors" We show that for multicomponent Ginzburg-Landau (GL) models the classification of superconductors into type-I and type-II is not sufficient. We obtain solutions representing thermodynamically stable vortex excitations in the two-component GL model which feature (i) non-monotonic interaction, (ii) for an n-quanta vortex, a non-monotonic ratio E(n)/n where E(n) is the energy per unit length, (iii) energetic preference for non-axisymmetric vortex states, ``vortex molecules". One physical consequence of the existence of these vortices is a first order transition into a "semi-Meissner" state: an inhomogeneous state of a mixture of domains of two-gap Meissner state and vortex clusters, where one of the order parameters is suppressed. E. Babaev cond-mat/0106360 Phys. Rev. Lett. 88 17702 (2002) "Dual neutral variables and knotted solitons in triplet superconductors" E. Babaev cond-mat/0404078 Phys. Rev. Lett. 94, 137001 (2005) "Fractional-flux vortices and spin superfluidity in triplet superconductor" We discuss a novel type of fractional flux vortices along with integer flux vortices in Kosterlitz-Thouless transitions in a triplet superconductor. We show that under certain conditions a spin-triplet superconductor should exhibit a novel state of spin superfluidity without superconductivity E. Babaev Phys. Rev. D 62, 074020 (2000)(hep-ph/0006087) "Nonlinear sigma model approach for chiral fluctuations and symmetry breakdown in Nambu-Jona-Lasinio model" J. Smiseth, E. Smorgrav, E. Babaev, Asle Sudbo "Field- and temperature induced topological phase transitions in the three-dimensional $N$-component London superconductor"" (cond-mat/0411761) Phys.Rev. B71 214509 (2005) E. Babaev Phys. Lett. B497 323 (2001) (hep-th/9907089) "Mass generation without symmetry breakdown in the Chiral Gross-Neveu Model at finite temperature and finite N ". see article confirming the existence of the pseudogap in this model n lattice simulations: S. Hands, J. Kogut C.Strouthos "The (2+1)-dimensional Gross-Neveu model with a U(1) chiral symmetry at nonzero temperature" Phys. Lett. B. 515 (2001) 407 E. Dahl, E. Babaev, A.Sudbo "Hidden vortex lattices in a thermally paired superfluid" arXiv:0807.0233 E. Dahl, E. Babaev, A.Sudbo "Unusual states of vortex matter in mixtures of Bose--Einstein Condensates on rotating optical lattices" arXiv:0810.3833 |