Research Statement

Strongly correlated electron materials

Andriy Nevidomskyy is a theoretical physicist working in the field of condensed matter. The focus of his study are materials in which electrons interact strongly with each other, resulting in a very different behaviour from ordinary metals such as aluminium and copper. One of the examples are the heavy fermion metals, so called because the electrically charged particles of which they consist, the fermions, are unlike ordinary electrons. The reason these electrons are unique, is because the interactions between them are so strong that they acquire a very heavy mass, often several hundred times greater than that of a bare electron. As a result of this heaviness, many material properties are profoundly affected. In particular, the electric current and thermal heat flow differently through these
materials at low temperatures. In addition, exotic quantum phases can form from this strange metallic state, such as unconventional superconductivity, that defy theoretical explanation.

The reason why most metals look qualitatively similar at cryogenic temperatures, is because their behavior is dictated by their lightest constituents – the electrons. Electrons obey special rules, and rather than being a gas of particles, they form what is called a Fermi liquid, or a Fermi sea. One can think of the response to an external probe as ripples and waves on the surface of this sea. In ordinary metals, these waves all look almost identical, described by the Landau Fermi liquid theory, which lies at the foundations of the modern theory of metals. The heavy fermion materials are different. They are typically composed of f-electron elements, such as cerium or plutonium, with CeCoIn₅, YbRh₂Si₂, PuCoGa₅ as examples. By applying pressure or chemical doping, these materials can be tuned to the so-called quantum phase transition, where a magnetic phase disappears at absolute zero temperature. It is near this special point that the strange metal state is formed and exotic phases, such as superconductivity, emerge.

To study the properties of these phases, Dr Nevidomskyy employs a combination of the realistic electron band theory, which takes into account the details of chemical and structural composition, and the state-of-the-art analytical and numerical techniques to solve the effective many-body problem. The methodologies used include the cluster dynamical mean-field theory (CDMFT), large-N expansion and Schwinger boson techniques. It is hoped that this combined approach will help shed light on the properties of the non-Fermi liquid `strange metal' state and accompanying emergent phenomena, such as the unconventional superconductivity. This research is relevant not only to the heavy fermion materials, but equally to the high-temperature superconductors in the family of cuprates and the recently discovered iron-based compounds.

A. Marcinkova, J. K. Wang, C. Slavonic, K. F. Kelly, A. H. Nevidomskyy, and E. Morosan, "Search for topological surface states in GeBi₂Te₄ single crystals" (in preparation).

A. V. Mialitsin, I. A. Solov'yov, A. I. Tóth, I. I. Mazin, A.H. Nevidomskyy, B. S. Dennis, and G. Blumberg, "Intertwined Order Parameters in a Charge-Ordered Superconductor" (under review)

A. H. Nevidomskyy, “Interplay of orbital and spin ordering in the iron pnictides”, preprint <http://arxiv.org/abs/1104.1747> (under review in Phys. Rev. Lett.).

A. Ramires, P. Coleman, A. H. Nevidomskyy, and A. M. Tsvelik, "β-YbAlB₄ : a critical nodal metal", Phys. Rev. Lett. 109, 176404 (2012).

E. Morosan, D. Natelson, A. H. Nevidomskyy, and Q. Si, "Strongly correlated materials", Advanced Materials 24, 4896-4923 (2012).

J. Wei, H. Ji, W. Guo, A. H. Nevidomskyy, and D. Natelson, “Hydrogen stabilization of metallic VO₂ in single-crystal nanobeams”,  

Nature Nanotechnology 7, 357–362 (2012).

R. Yu, Z. Wang, P. Goswami, A. H. Nevidomskyy, E. Abrahams and Q. Si, “Spin dynamics of a J₁-J₂-K model for the paramagnetic phase of iron pnictides”, Phys. Rev. B 86, 085148 (2012).

 S. Kasahara, H. J. Shi, K. Hashimoto, S. Tonegawa, Y. Mizukami, T. Shibauchi, K. Sugimoto, T. Fukuda, T. Terashima, A. H. Nevidomskyy, and Y. Matsuda, “Electronic nematicity above the structural and superconducting transition in BaFe₂(As_1-xP_x)₂”, Nature (London) 486, 382-385 (2012).

R. Flint, A. H. Nevidomskyy, and P. Coleman, "Composite pairing in a mixed valent two channel Anderson model", Phys. Rev. B 84, 064514 (2011).

Y. Matsumoto, S. Nakatsuji, K. Kuga, Y. Karaki, N. Horie, Y. Shimura, T. Sakakibara, A.H.Nevidomskyy, P. Coleman, "Quantum Criticality without Tuning in the Mixed Valence Compound β-YbAlB₄", Science, 331, 316-319 (2011).

P. Coleman and A.H. Nevidomskyy, "Frustration and the Kondo effect in heavy fermion materials", J. Low. Temp. Phys. 161, 182-202 (2010).

V.V. Poltavets, K. A. Lokshin, A.H. Nevidomskyy, M. Croft, T.A. Tyson, G. Hadermann, G.V. Tendeloo, T. Egami, G. Kotliar, N. ApRoberts-Warren, A.P. Dioguardi, N. J. Curro, and M. Greenblatt, "Bulk magnetic order in a two dimensional Ni¹⁺/Ni²⁺ (d⁹/d⁸) nickelate, isoelectronic with superconducting cuprates", Phys. Rev. Letters 104, 206403 (2010).

A.H. Nevidomskyy and P. Coleman, “Kondo resonance narrowing in d- and f-electron systems”, Phys. Rev. Letters 103, 147205 (2009).

A.H. Nevidomskyy and P. Coleman, "Layered Kondo lattice model for quantum critical β-YbAlB4", Phys. Rev. Letters 102, 077202 (2009).

Y. Filinchuk, A.H. Nevidomskyy, D. Chernyshov, and V. Dmitriev, “High-pressure phase and transition phenomena in ammonia borane NH₃BH₃ from x-ray diffraction, Landau theory, and ab initio calculations”, Phys. Rev. B 79, 214111 (2009).

A.H. Nevidomskyy, C. Scheiber, D. Senechal and A.-M. S. Tremblay, “Magnetism and d-wave superconductivity on the half-filled square lattice with frustration”, Phys. Rev. B 77, 064427 (2008).

A.H. Nevidomskyy, D. Senechal and A.-M. S. Tremblay, “Convexity of the self-energy functional in the variational cluster approximation”, Phys. Rev. B 77, 075105 (2008)

J. Linder, A.H. Nevidomskyy, M. Cuoco, A. Sudbo, and I. B. Sperstad, “Coexistence of itinerant ferromagnetism and a non-unitary superconducting state with line nodes: possible application to UGe₂”, Phys. Rev. B 77, 184511 (2008).

J. Linder, A.H. Nevidomskyy, and A. Sudbo, “Nontrivial interplay between superconductivity and spin-orbit coupling in non-centrosymmetric ferromagnets”, Phys. Rev. B 78, 172502 (2008).

Y. Filinchuk, D. Chernyshov, A.H. Nevidomskyy, and V. Dmitriev, ”High-pressure polymorphism as a step towards destabilization of LiBH₄”, Angew. Chemie 47, 529 (2007).

A.H. Nevidomskyy, “Coexistence of ferromagnetism and superconductivity near a quantum phase transition: The Heiseberg- to Ising-type crossover”, Phys. Rev. Letters 94, 097003 (2005).

G. Csanyi, P.B. Littlewood, A.H. Nevidomskyy, C. J. Pickard, and B. D. Simons, ”The role of the interlayer state in the electronic structure of super­conducting graphite intercalated compounds”, Nature Physics 1, 42-45 (2005).

A.H. Nevidomskyy, G. Csanyi, and M.C. Payne, “Chemically active substitutional nitrogen impurity in carbon nanotubes”, Phys. Rev. Letters 91, 105502 (2003).

Y. Matsumoto, S. Nakatsuji, K. Kuga, Y. Karaki, Y. Shimura, T. Sakakibara, A. H. Nevidomskyy, and P. Coleman, "T/B scaling of magnetization in the mixed valent compound beta-YbAlB₄", J. Phys.: Conf. Ser. 391 012041 (2012)

Invited speaker. "Fragile quantum criticality and T/B scaling in β-YbAlB₄", Hangzhou Workshop on Quantum Matter, Hangzhou, China (April 2011)

"The tale of two metals: quantum criticality in β-YbAlB4", Kent State University (April 2010)

"The tale of two metals: quantum criticality in β-YbAlB4", Ames Lab at Iowa State (Nov. 2010)

"Interplay of orbital and spin ordering in the iron pnictides", APS March Meeting, Dallas (March 2011)

"Interplay of orbital and spin ordering in the iron pnictides and ruthenates." Kyoto University, Japan (October 24, 2012).

"Fragile quantum criticality and T/B scaling in β-YbAlB4: a theorist's perspective", Physics seminar, UT Austin (October 2011)

"Fragile quantum criticality and T/B scaling in beta-YbAlB4: a theorist's perspective", Physics seminar, University of Maryland (April 2011)

"Fragile quantum criticality in β-YbAlB4: a theorist's perspective", Physics seminar, University Ruhr-Bochum, Bochum, Germany (June 2011)

"The tale of two metals: quantum criticality in β-YbAlB4", Rice University (February 2010)

"Interplay of orbital and spin ordering in the iron pnictides", Workshop at the Aspen Center for Physics (Aspen, Colorado), August 2011.