Bulletin of the American Physical Society
APS March Meeting 2016
Volume 61, Number 2
Monday–Friday, March 14–18, 2016; Baltimore, Maryland
Session R27: Non-Fermi-liquids |
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Sponsoring Units: DCMP Chair: Arkady Shekhter, Maglab, Florida State University Room: 326 |
Thursday, March 17, 2016 8:00AM - 8:12AM |
R27.00001: New phases from interacting Majorana fermions in one dimension Marcel Franz, Armin Rahmani, Xiaoyu Zhu, Ian Affleck Vortices in the Fu-Kane model (describing a superconducting surface of a 3D topological insulator) are known to host Majorana zero modes. By adjusting a single system parameter -- the global chemical potential -- the zero modes can be tuned to the regime of strong interactions. The simplest interacting system that can be built from these ingredients is a 1D Majorana chain with nearest neighbor hopping and the most local 4-fermion interaction. The system exhibits a complex phase diagram with interesting phases and phase transitions between them. For repulsive interactions we find an interesting gapless phase with coexisting Luttinger liquid and Ising degrees of freedom. The latter is separated from a 4-fold degenerate gapped phase at strong coupling by a novel generalization of the commensurate-incommensurate transition. [Preview Abstract] |
Thursday, March 17, 2016 8:12AM - 8:24AM |
R27.00002: Supersymmetry from Strongly Interacting Majoranas Armin Rahmani, Xiaoyu Zhu, Marcel Franz, Ian Affleck We show that a strongly interacting chain of Majorana zero modes exhibits a supersymmetric quantum critical point corresponding to the tricritical Ising model, separating the Ising critical phase from a doubly degenerate gapped phase. The supersymmetry extends into a gapped phase. We identify the signatures of our predictions in tunneling experiments. [Preview Abstract] |
Thursday, March 17, 2016 8:24AM - 8:36AM |
R27.00003: Quantum phase transition in a strongly interacting 2D model of Majorana fermions Bo-Hai Li, Shao-Kai Jian, Hong Yao Abstract: We study a 2D strongly-interacting time-reversal-invariant system consisting of Majorana fermions on the square lattice. This model may be realized as an Abrikosov vortex lattice in the superconducting surface state of a strong topological insulator. From the mean-field calculations, we show that for strong interactions a time-reversal-symmetry breaking phase occurs with chiral edge states. We further investigate the quantum critical behavior at the phase transition point by renormalization group analysis. [Preview Abstract] |
Thursday, March 17, 2016 8:36AM - 8:48AM |
R27.00004: Landau levels of Majorana fermions in a spin liquid Stephan Rachel, Lars Fritz, Matthias Vojta Majorana fermions, originally proposed as elementary particles acting as their own antiparticles, can be realized in condensed-matter systems as emergent quasiparticles, a situation often accompanied by topological order. Here we propose a physical system which realizes Landau levels – highly degenerate single-particle states usually resulting from an orbital magnetic field acting on charged particles – for Majorana fermions. This is achieved in a variant of a quantum spin system due to Kitaev which is distorted by triaxial strain. This strained Kitaev model displays a spin-liquid phase with charge-neutral Majorana-fermion excitations whose spectrum corresponds to that of Landau levels, here arising from a tailored pseudo-magnetic field. We show that measuring the dynamic spin susceptibility reveals the Landau-level structure by a remarkable mechanism of probe-induced bound-state formation. [Preview Abstract] |
Thursday, March 17, 2016 8:48AM - 9:00AM |
R27.00005: MOVED TO M1.377 |
Thursday, March 17, 2016 9:00AM - 9:12AM |
R27.00006: Johnson noise thermometry reveals the Dirac fluid in graphene Jesse Crossno, Jing Shi, Ke Wang, Xiaomeng Liu, Achim Harzheim, Andrew Lucas, Subir Sachdev, Philip Kim, Takashi Taniguchi, Kenji Watanabe, Thomas Ohki, Kin Chung Fong Near the charge neutrality point in graphene, the Fermi surface vanishes leading to the formation of a strongly-interacting quasi-relativistic electron-hole plasma, known as a Dirac fluid. These non-Fermi liquids share many features with quantum critical systems including a fast electron-electron scattering rate which makes them well suited to hydrodynamic descriptions. A number of exotic properties have been predicted including a diverging thermal conductivity resulting in the breakdown of the Wiedemann-Franz (WF) law. I will discuss the experimental technique---based on Johnson noise thermometry---used to measure the electronic thermal conductivity of graphene and probe the unique transport dynamics of the Dirac fluid. [Preview Abstract] |
Thursday, March 17, 2016 9:12AM - 9:24AM |
R27.00007: Transport in inhomogeneous quantum critical fluids and in the Dirac fluid in graphene Andrew Lucas, Jesse Crossno, Philip Kim, Subir Sachdev, Kin Chung Fong We present a hydrodynamic theory of transport in quantum critical fluids, disordered on long wavelengths due to fluctuations in the chemical potential. We argue that this approach is also well-suited to the Dirac fluid in graphene near the charge-neutrality point. Numerical simulations of this theory are compared to recent experiments on thermal and electric transport in clean samples of charge-neutral graphene. We obtain substantially improved quantitative agreement with data over existing hydrodynamic models. This provides evidence that the Dirac fluid behaves as a strongly interacting electronic fluid with transport governed by essentially classical collective phenomena. This work makes quantitative contact between AdS/CMT-inspired models of transport and an experimentally realized condensed matter system for the first time. [Preview Abstract] |
Thursday, March 17, 2016 9:24AM - 9:36AM |
R27.00008: Dimensional Crossover from 2D Fermi liquids to 1D Luttinger liquids Jia-Hua Gu, Kai Sun We demonstrate an analytic theory for the crossover between Fermi liquids and Luttinger liquids. By deforming the Fermi surface of a 2D Fermi liquid towards perfect nesting, we show that signatures of Luttinger liquids arise. In the crossover regime, bosonic particles emerge from the fermionic theory, whose the spectral weight characterize the crossover towards 1D Luttinger liquids. At perfect nesting, these bosonic modes recover the bosonizatoin formalism for Luttinger liquids. Spin-charge separation and instabilities due to attractive interactions are also studied. [Preview Abstract] |
Thursday, March 17, 2016 9:36AM - 9:48AM |
R27.00009: Numerical study on a random 4-fermion interaction model of a strange metal Wenbo Fu, Subir Sachdev We use exact diagonalization (ED) method to study the infinite range random 4 fermion model [1] of a strange metal. We examine the Green’s function and show that ED result is in agreement with the large N result in the scaling limit [2]. We also examine the thermal entropy; this has an increasing trend as we increase the system size in the low temperature regime, and is consistent with large N high temperature expansion in the high temperature regime. [1] S. Sachdev, arXiv:1506.05111 [2] S. Sachdev and J. Ye, Phys. Rev. Lett. 70, 3339 (1993) [Preview Abstract] |
Thursday, March 17, 2016 9:48AM - 10:00AM |
R27.00010: Electronic transport and Luttinger behavior in polymer thin films in the quasi-atomic limit Aaron Szasz, Roni Ilan, Joel Moore Recent experiments have shown two-dimensional polymer films to be promising materials for thermoelectric devices, but some of the observed properties are not well understood. To better understand these materials, we introduce a new model in which each polymer is a Luttinger liquid and the polymers are weakly coupled to each other. This approximation of strong interactions within each polymer and weak coupling between them is the ``quasi-atomic limit.'' We find integral expressions for transport coefficients, including the electrical and thermal conductivities and the thermopower, and we extract their power law dependencies on temperature. Luttinger liquid physics is manifested in a violation of the Wiedemann-Franz law. [Preview Abstract] |
Thursday, March 17, 2016 10:00AM - 10:12AM |
R27.00011: ABSTRACT WITHDRAWN |
Thursday, March 17, 2016 10:12AM - 10:24AM |
R27.00012: Universal Symmetry-Protected Resonances in a Spinful Luttinger Liquid Yichen Hu, Charles Kane We study the problem of resonant tunneling through a quantum dot in a spinful Luttinger liquid. It provides the simplest example of a $(0 + 1)$d system with symmetry-protected topological phases. Transitions between different symmetry-protected topological phases separated by fixed points are achieved by tuning the system through resonance. For a particular interaction strength (Luttinger parameter $g_\rho=\frac{1}{3}$, $g_\sigma=1$), we show that the problem is equivalent to a two channel $SU(3)$ Kondo problem. Both problems can be mapped to a quantum Brownian motion model on a Kagome lattice, which in turn is related to quantum Brownian motion on a honeycomb lattice and the three channel $SU(2)$ Kondo problem. Utilizing boundary conformal field theory, we find the universal peak conductance $g^* \frac{e^2}{h}$ as well as dimensions of the leading relevant operators of the problem. This allows us to compute the scaling behavior of the resonance line-shape as a function of temperature. We also established the fact that the fixed point quantum Brownian motion on both generalized honeycomb lattice($SU(2)_k$ Kondo) and generalized Kagome lattice($SU(k)_2$ Kondo) flow into are the same (with $k=3$ our original resonant tunneling problem). [Preview Abstract] |
Thursday, March 17, 2016 10:24AM - 10:36AM |
R27.00013: Structure of Inert Gases Adsorbed in MCM-41 Dylan Evans, Paul Sokol One-dimensional quantum liquids of $^{3}$He or $^{4}$He have generated recent interest for investigation in the Luttinger liquid model. Unfortunately, current studies lack a clear demonstration of definitively one-dimensional behavior. We propose using the templated, porous material, MCM-41, as a host for an atomic Luttinger liquid. In general, the pores of MCM-41 are too wide to provide a strictly one-dimensional environment, so we investigate preplating these pores with inert gases to effectively reduce their diameter. We present the results of studies of the structure of inert gases in MCM-41. Nitrogen sorption isotherms were used to characterize the sample. Then, using inert gases as adsorbates, we determined the minimum effective pore diameter that can be achieved in our sample before capillary condensation takes over. X-ray powder diffraction (XRD) was performed on the ideally preplated sample to investigate the structure of the adsorbates in the nanopores. The XRD measurements are compared to simulations of core-shell cylinder model scattering, and the validity of the model is assessed. The prospects for creating a definitively one-dimensional channel for the application of studying the structure and dynamics of helium confined in one dimension are discussed. [Preview Abstract] |
Thursday, March 17, 2016 10:36AM - 10:48AM |
R27.00014: Fractionally Charged Solitons in the t-J model on a diagonal two-leg ladder Yifan Jiang, Hongchen Jiang, Hong Yao, Steven Kivelson We define a new class of ''diagonal'' t-J ladders rotated by $\pi/4$ relatively to the canonical lattice directions of the square lattice, and study it using density matrix renormalization group (DMRG). We focus on the two-leg ladder with a doped hole concentration near $x=1/4$. At exactly $x=1/4$, the system forms a period 4 CDW and exhibits spin-charge separation. Slightly away from $1/4$ doping, we observe several topologically distinct types of solitons with well defined fractionalized quantum numbers. Remarkably, given the absence of any small parameters, the effective masses of the various emergent solitons differ by over four orders of magnitude. [Preview Abstract] |
Thursday, March 17, 2016 10:48AM - 11:00AM |
R27.00015: Non Fermi Liquid Crossovers in a Quasi-One-Dimensional Conductor in an Inclined Magnetic Field Andrei Lebed We consider a theoretical problem of electron-electron scattering time in a quasi-one-dimensional (Q1D) conductor in a magnetic field, perpendicular to its conducting axis. We show that inverse electron-electron scattering time becomes of the order of characteristic electron energy, $1/\tau \sim \epsilon \sim T$, in a high magnetic field, directed far from the main crystallographic axes, which indicates breakdown of the Fermi liquid theory. In a magnetic field, directed close to one of the main crystallographic axis, inverse electron-electron scattering time becomes much smaller than characteristic electron energy and, thus, applicability of Fermi liquid theory restores. We suggest that there exist crossovers between Fermi liquid and some non Fermi liquid states in a strong enough inclined magnetic field. Application of our results to the Q1D conductor (Per)$_2$Au(mnt)$_2$ shows that it has to be possible to observe the above mentioned phenomenon in feasibly high magnetic fields of the order of $H \geq H^* \simeq 25 \ T$. [Preview Abstract] |
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