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A. M. Tsvelik

Publications and source records attributed to A. M. Tsvelik.

At least 109 records · Page 6Linked to original sources
arXiv2007

Phenomenological theory of the underdoped phase of a high-T$_c$ superconductor

We model the Fermi surface of the cuprates by one-dimensional nested parts near $(0,π)$ and $(π,0)$ and unnested parts near the zone diagonals. Fermions in the nested regions form 1D spin liquids, and develop spectral gaps below some $\sim T^*$, but superconducting order is prevented by 1D phase fluctuations. We show that the Josephson coupling between order parameters at $(0,π)$ and $(π,0)$ locks their relative phase at a crossover scale $T^{**}< T^*$. Below $T^{**}$, the system response becomes two-dimensional, and the system displays Nernst effect. The remaining total phase gets locked at $T_c < T^{**}$, at which the system develops a (quasi-) long-range superconducting order.

cond-mat.supr-con↗
arXiv2006

Nonlinear magnetotransport in interacting chiral nanotubes

Nonlinear transport through interacting single-wall nanotubes containing a few impurities is studied theoretically. Extending the Luttinger liquid theory to incorporate trigonal warping and chirality effects, we derive the current contribution $I_e$ {\sl even} in the applied voltage $V$ and {\sl odd} in an orbital magnetic field $B$, which is non-zero only for chiral tubes and in the presence of interactions.

cond-mat.mes-hall↗
arXiv2006

Exactly solvable model for isospin S=3/2 fermionic atoms on an optical lattice

We propose an exact solution of a model describing a low energy behavior of cold isospin S=3/2 fermionic atoms on a one-dimensional optical lattice. Depending on the band filling the effective field theory has a form of a deformed Gross-Neveu model with either $O(7)\times \mathbb{Z}_2$ (half filling) or $U(1)\times O(5)\times \mathbb{Z}_2$ symmetry.

cond-mat.str-el↗
arXiv2006

Finite temperature correlation functions in integrable models: derivation of the semiclassical limit from the formfactor expansion

We propose an approach to the problem of finite temperature dynamical correlation functions in integrable one-dimensional models with a spectral gap. The approach is based on the analysis of the singularities of the operator matrix elements and is not model specific. For the long time, large distance asymptotics of the correlation functions we obtain a formula which, as a particular case, contains the expression for the dynamical susceptibility of Quantum Ising model suggested by Sachdev and Young, Phys. Rev. Lett. {\bf 78}, 2220 (1997).

cond-mat.stat-mech↗
arXiv2006

Low temperature correlation functions in integrable models: Derivation of the large distance and time asymptotics from the form factor expansion

We propose an approach to the problem of low but finite temperature dynamical correlation functions in integrable one-dimensional models with a spectral gap. The approach is based on the analysis of the leading singularities of the operator matrix elements and is not model specific. We discuss only models with well defined asymptotic states. For such models the long time, large distance asymptotics of the correlation functions fall into two universality classes. These classes differ primarily by whether the behavior of the two-particle S matrix at low momenta is diagonal or corresponds to pure reflection. We discuss similarities and differences between our results and results obtained by the semi-classical method suggested by Sachdev and Young, Phys. Rev. Lett. {\bf 78}, 2220 (1997).

cond-mat.stat-mech↗
arXiv2005

Self-energy of a nodal fermion in a d-wave superconductor

We re-consider the self-energy of a nodal (Dirac) fermion in a 2D d-wave superconductor. A conventional belief is that Im Σ(ω, T) \sim max (ω^3, T^3). We show that Σ(ω, k, T) for k along the nodal direction is actually a complex function of ω, T, and the deviation from the mass shell. In particular, the second-order self-energy diverges at a finite T when either ωor k-k_F vanish. We show that the full summation of infinite diagrammatic series recovers a finite result for Σ, but the full ARPES spectral function is non-monotonic and has a kink whose location compared to the mass shell differs qualitatively for spin-and charge-mediated interactions.

cond-mat.str-el↗
arXiv2005

Doped Spin Liquid: Luttinger Sum Rule and Low Temperature Order

We analyze a model of two-leg Hubbard ladders weakly coupled by interladder tunneling. At half filling a semimetallic state with small Fermi pockets is induced beyond a threshold tunneling strength. The sign changes in the single electron Green's function relevant for the Luttinger Sum Rule now take place at surfaces with both zeroes and infinities with important consequences for the interpretation of ARPES experiments. Residual interactions between electron and hole-like quasi-particles cause a transition to long range order at low temperatures. The theory can be extended to small doping leading to superconducting order.

cond-mat.str-el↗
arXiv2005

Crossed spin-1/2 Heisenberg chains as a quantum impurity problem

Using equivalencies between different models we reduce the model of two spin-1/2 Heisenberg chains crossed at one point to the model of free fermions. The spin-spin correlation function is calculated by summing the perturbation series in the interchain coupling. The result reveals a power law decay with a nonuniversal exponent.

cond-mat.str-el↗
arXiv2005

Excitation spectrum of doped two-leg ladders: A field theory analysis

We apply quantum field theory to study the excitation spectrum of doped two-leg ladders. It follows from our analysis that throughout most of the phase diagram the spectrum consists of degenerate quartets of kinks and anti-kinks and a multiplet of vector particles split according to the symmetry of the problem as 3 + 2 +1. This basic picture experiences corrections when one moves through the phase diagram. In some regions the splitting may become very small and in others it is so large that some multiplets are pushed in the continuum and become unstable. At second order transition lines masses of certain particles vanish. Very close to the first order transition line additional generations of particles emerge. Strong interactions in some sectors may generate additional bound states (like breathers) in the asymmetric charge sector. We briefly describe the properties of various correlation functions in different phases.

cond-mat.str-el↗
arXiv2005

Paperclip at $θ=π$

We study the ``paperclip'' model of boundary interaction with the topological angle $θ$ equal to $π$. We propose exact expression for the disk partition function in terms of solutions of certain ordinary differential equation. Large distance asymptotic form of the partition function which follows from this proposal makes it possible to identify the infrared fixed point of the paperclip boundary flow at $θ=π$.

hep-th↗
arXiv2005

A strange metal with a small Fermi surface and strong collective excitations

We develop a theory of a hybrid state, where quasi-particles coexist with strong collective modes, taking as a starting point a model of infinitely many 1D Mott insulators coupled by a weak interchain tunneling. This state exists at an intermediate temperature range and undergoes an antiferromagnetic phase transition at temperatures much smaller than the Mott-Hubbard gap. The most peculiar feature of the hybrid state is that the volume of the Fermi surface is unrelated to the electron density. We present a self-consistent derivation of the low energy effective action for our model.

cond-mat.supr-con↗
arXiv2004

Aspects of Confinement in Low Dimensions

We briefly review some examples of confinement which arise in condensed matter physics. We focus on two instructive cases: the off-critical Ising model in a magnetic field, and an array of weakly coupled (extended) Hubbard chains in the Wigner crystal phase. In the appropriate regime, the elementary excitations in these 1+1 and quasi-one-dimensional systems are confined into `mesons'. Although the models are generically non-integrable, quantum mechanics and form factor techniques yield valuable information.

cond-mat.str-el↗
arXiv2004

Confinement and deconfinement of spinons in a frustrated spin-1/2 Heisenberg model

In this publication I discuss the phase diagram of a frustrated spin-1/2 Heisenberg model suggested in A. A. Nersesyan and A. M. Tsvelik, Phys. Rev. B{\bf 67}, 024422 (2003). The phase diagram contains $(π,0)$ and $(π,π)$ antiferromagnetic phases separated by the Valence Bond Crystal (VBC) state. I argue that the point of the phase diagram with deconfined spinons, predicted in the aforementioned work, is situated in the middle of VBC state, at the point where the dimerization order parameter changes sign.

cond-mat.str-el↗
arXiv2004

Finite temperature spectral function of Mott insulators and CDW States

We calculate the low temperature spectral function of one-dimensional incommensurate charge density wave (CDW) states and half-filled Mott insulators (MI). At $T=0$ there are two dispersing features associated with the spin and charge degrees of freedom respectively. We show that already at very low temperatures (compared to the gap) one of these features gets severely damped. We comment on implications of this result for photoemission experiments.

cond-mat.str-el↗
arXiv2003

Theory of Optical Transmission Through a Near-Field Probe With a Dissipative Matter in its Core

We develop a theory of light transmission through an aperture-type near-field optical probe with a dissipative matter in its semiconducting core described by a complex frequency-dependent dielectric function. We evaluate the near-field transmission coefficient of a metallized silicon probe with a large taper angle of in the visible and near-infrared wavelength range. It is shown that in this spectral range the use of a short silicon probe instead of a glass one allows to achieve a strong (up to 10$^2-10^{3}$) enhancement in the transmission efficiency.

physics.optics↗
arXiv2003

Coulomb Blockade Regime of a Single-Wall Nanotube

A model of carbon nanotube at half filling is studied. The Coulomb interaction is assumed to be unscreened. It is shown that this allows to develop the adiabatic approximation which leads to considerable simplifications in calculations of the excitation spectrum. We give a detailed analysis of the spectrum and the phase diagram at half filling and discuss effects of small doping. At small doping several phases develop strong superconducting fluctuations corresponding to various types of pairing.

cond-mat.str-el↗