Bulletin of the American Physical Society
APS March Meeting 2015
Volume 60, Number 1
Monday–Friday, March 2–6, 2015; San Antonio, Texas
Session F22: Transport and Theory of NonFermi liquids 
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Sponsoring Units: DCMP Room: 202A 

F22.00001: ABSTRACT WITHDRAWN 
Tuesday, March 3, 2015 8:12AM  8:24AM 
F22.00002: Kondo Effects in Single Layer Transition Metal Dichalcogenides Michael Phillips, Vivek Aji Inversion symmetry breaking and strong spin orbit coupling in two dimensional transition metal dichalcogenides leads to interesting new phenomena such as the valley hall and spin hall effects. They display optical circular dichroism and the ability to generate excitation with valley specificity. In this talk we report on the consequences of these properties on correlated states in hole doped systems focussing on the physics of the screening of magnetic impurities. Unlike typical metals, the breaking of inversion symmetry leads to the mixing of a triplet component to the Kondo cloud. Using a variational wave function approach we determine the nature of the many body state. With the ground state in hand we analyze the excitations generated by valley discriminating perturbations. [Preview Abstract] 
Tuesday, March 3, 2015 8:24AM  8:36AM 
F22.00003: NonFermiliquid behavior and anomalous suppression of Landau damping in layered metals close to ferromagnetism Sam Ridgway, Chris Hooley We analyse the lowenergy physics of nearly ferromagnetic metals in two spatial dimensions using the functional renormalization group technique. We find a new class of lowenergy fixed point, at which the fermionic (electronlike) excitations are nonFermiliquid ($z_f = 7/6$) and the magnetic fluctuations exhibit an anomalous Landau damping whose rate vanishes as $\Gamma_{\bf q} \sim \vert {\bf q} \vert^{1/3}$ in the low$\vert {\bf q} \vert$ limit. We discuss the physical nature of this fixed point, and highlight its possible applicability to experiments on UGe$_2$ and related compounds. [Preview Abstract] 
Tuesday, March 3, 2015 8:36AM  8:48AM 
F22.00004: Stable nonFermi liquid phase of itinerant spinorbit coupled ferromagnets Yasaman Bahri, Andrew Potter Direct coupling between gapless bosons and a Fermi surface results in the destruction of Landau quasiparticles and a breakdown of Fermi liquid theory. Such a nonFermi liquid phase arises in spinorbit coupled ferromagnets with spontaneously broken continuous symmetries due to strong coupling between rotational Goldstone modes and itinerant electrons. These systems provide an experimentally accessible context for studying nonFermi liquid physics. Possible examples include lowdensity Rashba coupled electron gases, which have a natural tendency towards spontaneous ferromagnetism, or topological insulator surface states with proximityinduced ferromagnetism. Crucially, unlike the related case of a spontaneous nematic distortion of the Fermi surface, for which the nonFermi liquid regime is expected to be masked by a superconducting dome, we show that the nonFermi liquid phase in spinorbit coupled ferromagnets is stable. [Preview Abstract] 
Tuesday, March 3, 2015 8:48AM  9:00AM 
F22.00005: DoubleExchange physics in NonFermiLiquid FeCrAs Patrick O'Brien, Turan Birol, Shivam Ghosh, Michael Lawler We focus on the problem of determining the microscopic physics of the bad antiferromagnetic metal FeCrAs[1]. It has been argued to be underscreened Kondolike[2] due to large spin moments on the Cr atoms. Using LDA+U, we show that indeed Kondolike physics is likely. In particular, we find the band structure and Fermi surface to be hypersensitive to small changes in the Hund's coupling J with little evidence for crystal field splitting. We then propose a simple three dimensional lattice model using hybrid orbital ideas to capture hopping parameters and a Kondo coupling to capture the limit where J is larger than the crystal field splitting. This model is therefore distinct from one proposed in Ref. [3] which assumes J is less than the crystal field splitting. We chose its parameters based on a best fit to the DFT results and use it to study the stability of the observed $\sqrt{3}\times\sqrt{3}$ magnetic order on the kagomelike Cr lattice as a test of the model. [1] W. Wu et al, 2009 EPL 85 17009 [2] A. Akrap et al, Phys. Rev. B 89, 125115 [3] J.G. Rau and H.Y. Kee, Phys. Rev. B 84, 104448 [Preview Abstract] 
Tuesday, March 3, 2015 9:00AM  9:12AM 
F22.00006: NonFermi liquid behavior from dynamical effects of impurity scattering in correlated Fermi liquids Vidhyadhiraja Narsimha Murthy Sudhindra, Pramod Kumar The interplay of disorder and interactions is a subject of perennial interest. In this work, we have investigated the effect of disorder due to chemical substitution on the dynamics and transport properties of correlated Fermi liquids. A low frequency analysis in the concentrated and dilute limits shows that the dynamical local potentials arising through disorder averaging generate a linear (in frequency) term in the scattering rate. Such nonFermi liquid behavior (nFL) is investigated in detail for Kondo hole substitution in heavy fermions within dynamical mean field theory. Analytical expressions in limiting cases and numerical solutions of the dynamical mean field theory equations reveal that the nFL term will show up significantly only in certain regimes, although it is present for any nonzero disorder concentration in principle. Remarkably, we find that the nFL behavior due to dynamical effects of impurity scattering has features that are distinct from those arising through Griffiths singularities or distribution of Kondo scales. Relevance of our findings to experiments on alloyed correlated systems is pointed out. [Preview Abstract] 
Tuesday, March 3, 2015 9:12AM  9:24AM 
F22.00007: Melting of Boltzmann particles in different 2D trapping potential Dyuti Bhattacharya, Alexei Filinov, Amit Ghosal, Michael Bonitz We analyze the quantum melting of two dimensional Wigner solid in several confined geometries and compare them with corresponding thermal melting in a purely classical system. Our results show that the geometry play little role in deciding the crossover quantum parameter $n_X$, as the effects from boundary is well screened by the quantum zero point motion. The unique phase diagram in the plane of thermal and quantum fluctuations determined from independent melting criteria separates out the Wigner molecule ``phase" from the classical and quantum ``liquids". An intriguing signature of weakening liquidity with increasing temperature $T$ have been found in the extreme quantum regime ($n$). This crossover is associated with production of defects, just like in case of thermal melting, though the role of them in determining the mechanism of the crossover appears different. Our study will help comprehending melting in a variety of experimental realization of confined system  from quantum dots to complex plasma. [Preview Abstract] 
Tuesday, March 3, 2015 9:24AM  9:36AM 
F22.00008: Finite Temperature Transport in a NonFermi Liquid Phase of a Quadratic Semimetal Philipp Dumitrescu We study finite temperature transport in the LuttingerAbrikosovBeneslavskii phase  an interacting, scale invariant, nonFermi liquid phase found in quadratic semimetals which has been recently suggested to be realized in strongly correlated pyrochlore iridate systems. We develop a kinetic equation formalism to describe the d.c. transport properties, which are dominated by collisions, and consider the shear viscosity $\eta$ as a model transport coefficient. The ratio of shear viscosity to entropy density $\eta/s$ is a measure of the strength of interaction between the excitations of a quantum fluid. As a consequence of the quantum critical nature of the system, $\eta / s$ is a universal number and we find it to be consistent with a bound proposed from gaugegravity duality. [Preview Abstract] 
Tuesday, March 3, 2015 9:36AM  9:48AM 
F22.00009: Transport in twodimensional disordered semimetals Michael Knap, Jay D. Sau, Bertrand I. Halperin, Eugene Demler We theoretically study transport in twodimensional semimetals. Typically, electron and hole puddles emerge in the transport layer of these systems due to smooth fluctuations in the potential. We calculate the electric response of the electronhole liquid subject to zero and finite perpendicular magnetic fields using an effective medium approximation and a complimentary mapping on resistor networks. In the presence of smooth disorder and in the limit of weak electronhole recombination rate, we find for small but finite overlap of the electron and hole bands an abrupt upturn in resistivity when lowering the temperature but no divergence at zero temperature. We discuss how this behavior is relevant for several experimental realizations and introduce a simple physical explanation for this effect. [Preview Abstract] 
Tuesday, March 3, 2015 9:48AM  10:00AM 
F22.00010: Phase diagram of a semimetal in the magnetic ultraquantum limit Aldo Isidori, Frank Arnold, Erik Kampert, Ben Yager, Matthias Eschrig, John Saunders Semimetals like graphite have recently received compelling interest as they not only are able to host topologically nontrivial phases but also can be driven into the ultraquantum limit by magnetic fields now achievable in modernday laboratories. Thus, they provide insight into quantumHall physics and the physics of massless Dirac fermions in three dimensions. They also represent ideal model systems for studying magneticfield driven density wave instabilities, as the onset field for such collective excitations is suppressed in semimetals. Using pulsed highmagnetic fields up to 60 T applied to a single crystal of natural Tanzanian graphite, we find a series of fieldinduced phase transitions into collinear chargedensity wave states resulting from enhanced interactions between the lowest four Landau levels. By analysing magnetotransport data and calculating the renormalized Landau level structure at high fields, we establish the phase diagram of graphite in its ultraquantum limit. Our results imply the existence of a topologicallyprotected chiral edge state at high fields supporting both charge and spin currents. [Preview Abstract] 
Tuesday, March 3, 2015 10:00AM  10:12AM 
F22.00011: Novel understanding for the transitions in the ultraquantum limit of graphite Zengwei Zhu, Ross McDonald, Arkady Shekhter, Brad Ramshaw, Kimberly Modic, Fedor Balakirev, Neil Harrison A fascinating transition was documented in the ultraquantum limit of graphite between 22T and 53T. Recently, another unexpected highfield transition was observed around 75T. The relative simple band structure, though the complicated phase transitions, suggesting more researches should be carried out to understand the mysterious transitions. We performed temperature and angledependent inplane and outofplane magnetoresistance measurements in the ultraquantum limit on graphite. Our experiments reveal the transition between 22T and 53T is more complicating and interesting than the previous reports. We explain the cause of the transition properly with novel understanding. [Preview Abstract] 
Tuesday, March 3, 2015 10:12AM  10:24AM 
F22.00012: Nonperturbative Complete Energy Eigenbasis for Strongly Coupled Systems Anthony Hegg, Philip Phillips We develop a nonpertrubative approach to the strongly coupled $\phi^4$ theory by using an eigenenergy basis that solves the full equations of motion. By rewriting the action in terms of this basis we are able to implement a nonperturbative ``energyshell'' renormalization procedure, which yields a critical exponent of $\nu=0.6308$. We then identify and characterize an additional fixed point at even stronger coupling. All flows are relevant at this additional fixed point and the correlation exponent $\nu=\frac{2}{3}$ in three dimensions. We then discuss the differences between the value obtained for the anomalous dimension $\eta=0.10$ and that found in the literature $\eta=0.03$. Finally we report precise mean field exponents and logarithmic corrections in four dimensions. [Preview Abstract] 
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