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Jun 29, 2018
06/18

by
S. A. Owerre

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Motivated by the fact that many bilayer quantum magnets occur in nature, we generalize the study of thermal Hall transports of spin excitations to bilayer magnetic systems. It is shown that bilayer magnetic systems can be coupled either ferromagnetically or antiferromagnetically. We study both scenarios on the honeycomb lattice and show that the system realizes topologically nontrivial magnon bands induced by alternating next-nearest-neighbour Dzyaloshinsky-Moriya interaction (DMI). As a...

Topics: Condensed Matter, Strongly Correlated Electrons

Source: http://arxiv.org/abs/1604.05292

0
0.0

Jun 29, 2018
06/18

by
S. A. Owerre

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The experimental observation of topological magnon bands and thermal Hall effect in a kagom\'e lattice ferromagnet Cu(1-3, bdc) has inspired the search for topological magnon effects in various insulating ferromagnets that lack an inversion center allowing a Dzyaloshinskii-Moriya (DM) spin-orbit interaction. The star lattice (also known as the decorated honeycomb lattice) ferromagnets is an ideal candidate for this purpose because it is a variant of the kagom\'e lattice with additional links...

Topics: Mesoscale and Nanoscale Physics, Condensed Matter

Source: http://arxiv.org/abs/1606.04904

0
0.0

Jun 29, 2018
06/18

by
S. A. Owerre

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We study the quantum Kagom\'e ice hardcore bosons, which corresponds to the XY limit of quantum spin ice Hamiltonian. We estimate the values of the zero-temperature thermodynamic quantities using the large-$S$ expansion. We show that our semi-classical analysis is consistent with finite temperature quantum Monte Carlo estimates.

Topics: Condensed Matter, Strongly Correlated Electrons

Source: http://arxiv.org/abs/1604.02633

0
0.0

Jun 28, 2018
06/18

by
S. A. Owerre

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Motivated by recent quantum Monte Carlo (QMC) simulations of the quantum Kagome ice model by Juan Carrasquilla, et al., [Nature Communications 6, 7421 (2015)], we study the ground state properties of this model on the triangular lattice. In the presence of a magnetic field $h$, the Hamiltonian possesses competing interactions between a $Z_2$-invariant easy-axis ferromagnetic interaction $J_{\pm\pm}$ and a frustrated Ising term $J_z$. As in the U(1)-invariant model, we obtain four classical...

Topics: Strongly Correlated Electrons, Condensed Matter

Source: http://arxiv.org/abs/1511.01843

0
0.0

Jun 29, 2018
06/18

by
S. A. Owerre

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It has been recently shown that in the Heisenberg (anti)ferromagnet on the honeycomb lattice, the magnons (spin wave quasipacticles) realize a massless two-dimensional (2D) Dirac-like Hamiltonian. It was shown that the Dirac magnon Hamiltonian preserves time-reversal symmetry defined with the sublattice pseudo spins and the Dirac points are robust against magnon-magnon interactions. The Dirac points also occur at nonzero energy. In this paper, we propose a simple realization of nontrivial...

Topics: Condensed Matter, Strongly Correlated Electrons

Source: http://arxiv.org/abs/1602.06772

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0.0

Jun 29, 2018
06/18

by
S. A. Owerre

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In frustrated magnets the Dzyaloshinsky-Moriya interaction arising from spin-orbit coupling can induce a magnetic long-range order. Here, we report a theoretical prediction of thermal Hall effect in frustrated kagom\'e magnets such as KCr$_3$(OH)$_6$(SO4)$_2$ and KFe$_3$(OH)$_{6}$(SO$_{4}$)$_2$. The thermal Hall effects in these materials are induced by scalar spin chirality as opposed to DMI in previous studies. The scalar spin chirality originates from magnetic-field-induced chiral spin...

Topics: Condensed Matter, Strongly Correlated Electrons

Source: http://arxiv.org/abs/1608.04561

0
0.0

Jun 29, 2018
06/18

by
S. A. Owerre

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Topological magnon bands and magnon Hall effect in insulating collinear ferromagnets are induced by the Dzyaloshinskii-Moriya interaction (DMI) even at zero magnetic field. In the geometrically frustrated star lattice, a coplanar/noncollinear $\mathbf q=0$ magnetic ordering may be present due to spin frustration. This magnetic structure, however, does not exhibit topological magnon effects even with DMI in contrast to collinear ferromagnets. We show that a magnetic field applied perpendicular...

Topics: Condensed Matter, Strongly Correlated Electrons

Source: http://arxiv.org/abs/1608.08605

0
0.0

Jun 28, 2018
06/18

by
S. A. Owerre

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We use spin wave theory to investigate the ground state properties of the $Z_2$-invariant quantum XXZ model on the triangular lattice in the ferromagnetic phase. The Hamiltonian comprises nearest and next-nearest-neighbour Ising couplings, external magnetic fields, and a $Z_2$-invariant ferromagnetic coupling. We show that quantum fluctuations are suppressed in this system, hence linear spin wave theory gives reasonable estimates of the ground state thermodynamic properties. Our results show...

Topics: Strongly Correlated Electrons, Condensed Matter

Source: http://arxiv.org/abs/1511.02311

1
1.0

Jun 29, 2018
06/18

by
S. A. Owerre

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We investigate the nature of a $Z_2$-invariant XY ring-exchange interaction with a frustrated Ising coupling on the triangular lattice. In the limit of pure XY ring-exchange interaction, we show that the classical ground state is degenerate resulting from the $Z_2$-invariance of the Hamiltonian. Quantum fluctuations lift these classical degenerate ground states and produce an unusual state whose excitation spectrum exhibits a gapped maximum quadratic dispersion near ${\bf k}=0$ and vanishes at...

Topics: Condensed Matter, Strongly Correlated Electrons

Source: http://arxiv.org/abs/1603.04208

0
0.0

Jun 29, 2018
06/18

by
S. A. Owerre

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This paper presents a connection between the topological properties of hardcore bosons and that of magnons in quantum spin magnets. We utilize the Haldane-like hardcore bosons on the honeycomb lattice as an example. We show that this system maps to a spin-$1/2$ quantum XY model with a next-nearest-neighbour Dzyaloshinsky-Moriya interaction. We obtain the magnon excitations of the quantum spin model and compute the edge states, Berry curvature, thermal and spin Nernst conductivities. Due to the...

Topics: Condensed Matter, Strongly Correlated Electrons

Source: http://arxiv.org/abs/1603.06495

1
1.0

Jun 30, 2018
06/18

by
S. A. Owerre

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In this Letter, we identify a noncoplanar chiral spin texture on the distorted kagom\'e-lattice antiferromagnets induced by the presence of a magnetic field applied perpendicular to the distorted kagom\'e plane. The noncoplanar chiral spin texture has a nonzero scalar spin chirality similar to a chiral quantum spin liquid with broken time-reversal symmetry. In the noncoplanar regime we observe nontrivial topological magnetic excitations and thermal Hall response through the emergent...

Topics: Strongly Correlated Electrons, Condensed Matter

Source: http://arxiv.org/abs/1701.05199

0
0.0

Jun 29, 2018
06/18

by
S. A. Owerre

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Topological magnon insulators in insulating Kagom\'e ferromagnets have been extensively studied in a series of papers. It has been established that Dzyaloshinskii-Moriya interaction (DMI) is the key ingredient to observe a nontrivial topological magnon with edge modes. However, insulating antiferromagnets on the Kagom\'e lattice are frustrated systems considered as a playground for studying quantum spin liquid physics. In these systems the DMI can induce a coplanar but noncollinear magnetic...

Topics: Condensed Matter, Strongly Correlated Electrons

Source: http://arxiv.org/abs/1609.03563

0
0.0

Jun 29, 2018
06/18

by
S. A. Owerre

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Quite recently, magnon Hall effect of spin excitations has been observed experimentally on the kagome and pyrochlore lattices. Thermal Hall conductivity $\kappa^{xy}$, changes sign as a function of magnetic field or temperature on the kagome lattice, and $\kappa^{xy}$ changes sign upon reversing the sign of the magnetic field on the pyrochlore lattice. Motivated by these recent exciting experimental observations, we theoretically propose a simple realization of magnon Hall effect in a two-band...

Topics: Condensed Matter, Strongly Correlated Electrons

Source: http://arxiv.org/abs/1603.04331

0
0.0

Jun 29, 2018
06/18

by
S. A. Owerre

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Quantum Monte Carlo (QMC) simulation has uncovered nonzero Berry curvature and bosonic edge states in hardcore-Bose-Hubbard model on the gapped honeycomb lattice. The competition between the chemical potential and staggered onsite potential leads to an interesting quantum phase diagram comprising superfluid phase, Mott insulator, and charge density wave insulator. In this paper, we present a semiclassical perspective of this system by mapping to a spin-$1/2$ quantum XY model. We give an...

Topics: Condensed Matter, Strongly Correlated Electrons

Source: http://arxiv.org/abs/1603.07989

1
1.0

Jun 29, 2018
06/18

by
S. A. Owerre

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We investigate an ultra-thin film of topological insulator (TI) multilayer as a model for a three-dimensional (3D) Weyl semimetal. We introduce tunneling parameters $t_S$, $t_\perp$, and $t_D$, where the former two parameters couple layers of the same thin film at small and large momenta, and the latter parameter couples neighbouring thin film layers along the $z$-direction. The Chern number is computed in each topological phase of the system and we find that for $t_S,t_D>0$, the tunneling...

Topics: Mesoscale and Nanoscale Physics, Condensed Matter, Strongly Correlated Electrons

Source: http://arxiv.org/abs/1602.00618

3
3.0

Jun 26, 2018
06/18

by
S. A. Owerre; J. Nsofini

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In this Communication, we investigate a toy model of three-dimensional topological insulator surface, coupled homogeneously to a fictitious pseudo spin-$\frac{1}{2}$ particle. We show that this toy model captures the interesting features of topological insulator surface states, which include topological quantum phase transition and quantum spin hall effect. We further incorporate an out-of-plane magnetic field and obtain the Landau levels.

Topics: Other Condensed Matter, Condensed Matter, Mesoscale and Nanoscale Physics

Source: http://arxiv.org/abs/1501.02643

0
0.0

Jun 30, 2018
06/18

by
S. A. Owerre

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An antiferromagnetically exchange-coupled dimer of single molecule magnets which possesses a large spin tunneling has been investigated. For this system the ground and first excited states are entangled states and the Hamiltonian is effectively similar to that of a two-state system at $2s^{\text{th}}$ order in perturbation theory, thus this system can be mapped to an entangled pseudospin 1/2 particles. We study the effects of interaction and rotation of this system about its staggered easy-axis...

Topics: Quantum Physics, Mesoscale and Nanoscale Physics, Condensed Matter

Source: http://arxiv.org/abs/1402.2687

0
0.0

Jun 30, 2018
06/18

by
S. A. Owerre

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We study a molecular dimer model that takes higher order interaction term as well as antisymmetric term into account. We mainly focus on the theoretical quantum properties that are of interest. We numerically diagonalize the system and investigate different phenomena which include oscillations of ground state energy splitting, magnetization steps, Schottky anomaly, torque oscillations, and magnetocaloric effects. Indeed, we show that these interactions can exotically influence these phenomena,...

Topics: Mesoscale and Nanoscale Physics, Strongly Correlated Electrons, Condensed Matter

Source: http://arxiv.org/abs/1411.6555

0
0.0

Jun 29, 2018
06/18

by
S. A. Owerre

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In this Letter, we study the magnetic transport in AA-stacked bilayer honeycomb chiral magnets coupled either ferromagnetically or antiferromagnetically. For both couplings, we observe chirality-induced gaps, chiral protected edge states, magnon Hall and magnon spin Nernst effects of magnetic spin excitations. For ferromagnetically coupled layers, thermal Hall and spin Nernst conductivities do not change sign as function of magnetic field or temperature similar to single-layer honeycomb...

Topics: Mesoscale and Nanoscale Physics, Condensed Matter, Strongly Correlated Electrons

Source: http://arxiv.org/abs/1605.07971

0
0.0

Jun 29, 2018
06/18

by
S. A. Owerre

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In ultra-thin film of topological insulator, the hybridization between the top and bottom surfaces opens an energy gap and forms two degenerate quantum anomalous Hall states, which give rise to a quantum spin Hall state. In this paper, we demonstrate that a Weyl semimetal can be realized in an ultra-thin film of topological insulator heterostructure in a similar way to that of the surface state of a strong three-dimensional (3D) topological insulator studied by Burkov and Balents . We find that...

Topics: Mesoscale and Nanoscale Physics, Condensed Matter, Strongly Correlated Electrons

Source: http://arxiv.org/abs/1601.03707

2
2.0

Jun 28, 2018
06/18

by
S. A. Owerre

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We study the physics of quantum spin Hall (QSH) effect and topological quantum phase transition on the porphyrin lattice. We show that in a special limit the pristine model on this lattice reduces to the usual topological insulator (TI) thin film model. By incorporating explicit time reversal symmetry (TRS) breaking interactions, we explore the topological properties of this model and show that it exhibits an ordinary insulator phase, a quantum anomalous Hall (QAH) phase, and a quantum spin...

Topics: Quantum Physics, Mathematical Physics, Condensed Matter, High Energy Physics - Lattice,...

Source: http://arxiv.org/abs/1506.09204

2
2.0

Jun 26, 2018
06/18

by
S. A. Owerre; J. Nsofini

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In recent years, studies on cyclic molecular nanomagnets have captivated the attention of researchers. These magnets are finite in size and contain very large spins. They are interesting because they possess macroscopic quantum tunneling of N\'eel vectors. For antiferromagnetic molecular nanomagnets with finite number of even-numbered coupled spins, tunneling involves two classical localized N\'eel ground states separated by a magnetic energy barrier. The question is: can such phenomena be...

Topics: Strongly Correlated Electrons, Mesoscale and Nanoscale Physics, Condensed Matter

Source: http://arxiv.org/abs/1502.05684

0
0.0

Jun 30, 2018
06/18

by
S. A. Owerre; M. B. Paranjape

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We consider the one dimensional, periodic spin chain with $N$ sites, similar to the one studied by Haldane \cite{hal}, however in the opposite limit of very large anisotropy and small nearest neighbour, anti-ferromagnetic exchange coupling between the spins, which are of large magnitude $s$. For a chain with an even number of sites we show that actually the ground state is non degenerate and given by a superposition of the two N\'eel states, due to quantum spin tunnelling. With an odd number of...

Topics: Strongly Correlated Electrons, Condensed Matter

Source: http://arxiv.org/abs/1404.6706

1
1.0

Jun 30, 2018
06/18

by
S. A. Owerre; M. B. Paranjape

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This article presents a review on the theoretical and the experimental developments on macroscopic quantum tunneling and phase transition of the escape rate in spin systems. We present the basic ideas with simplified calculations so that it is readable to both specialists and nonspecialists in this area of research. A brief derivation of the path integral formulation of quantum mechanics in its original form using the orthonormal position and momentum basis is reviewed. For spin systems such as...

Topics: Quantum Physics, High Energy Physics - Theory, Other Condensed Matter, Condensed Matter

Source: http://arxiv.org/abs/1403.4208

1,883
1.9K

Sep 28, 2013
09/13

by
Ben Simons

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Outstanding free lecture notes on quantum field theory of condensed matter by Ben Simons (University of Cambridge). With lecture slides and problem sets. FreeScience.info ID: 975 Obtained From: http://www.tcm.phy.cam.ac.uk/~bds10/tp3.html http://freescience.info/go.php?pagename=books&id=975 Contents: Preface Chapter 1: Collective Excitations: From Particles to Fields Chapter 2: Second Quantisation Chapter 3: Feynman Path Integral Chapter 4: Functional Field Integral Chapter 5: Broken...

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Topics: many-body physics, quantum field theory, condensed matter physics, FreeScience.info collection,...

87
87

Nov 14, 2013
11/13

by
Ben Simons

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The aim of this course is to develop the machinery to explore the properties of quantum systems with very large or in�nite numbers of degrees of freedom. To represent such systems it is convenient to abandon the language of individual elementary particles and speak about quantum �elds. In this lecture, we will consider the simplest physical example of a free or non-interacting many-particle theory theory which will exemplify the language of classical and quantum �elds. Our starting point...

Topics: Physics, Condensed Matter, Particle Physics and Fields, General Theory of Fields and Particles,...

Source: http://www.flooved.com/reader/3059

0
0.0

Jun 30, 2018
06/18

by
S. A. Owerre; M. B. Paranjape

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We study the model of a biaxial single ferromagnetic spin Hamiltonian with an external magnetic field applied along the medium axis. The phase transition of the escape rate is investigated. Two different but equivalent methods are implemented. Firstly, we derive the semi-classical description of the model which yields a potential and a coordinate dependent mass. Secondly, we employ the method of spin-particle mapping which yields a similar potential to that of semi-classical description but...

Topics: Mesoscale and Nanoscale Physics, Statistical Mechanics, Condensed Matter

Source: http://arxiv.org/abs/1403.4440

83
83

Nov 14, 2013
11/13

by
Ben Simons

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Connection of Path Integral to Classical Statistical Mechanics Consider �exible string held under constant tension and con�ned to �gutter� potential...

Topics: Physics, Condensed Matter, Particle Physics and Fields, Quantum Physics, General Theory of Fields...

Source: http://www.flooved.com/reader/3050

96
96

Nov 14, 2013
11/13

by
Ben Simons

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Quantum Particle in a Single (Symmetric) Well:...

Topics: Physics, Condensed Matter, Particle Physics and Fields, Quantum Physics, General Theory of Fields...

Source: http://www.flooved.com/reader/3051

91
91

Nov 14, 2013
11/13

by
Ben Simons

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Having established that the low energy properties of the atomic chain are represented by a free scalar classical �eld theory, we now turn to the formulation of the quantum system.

Topics: Physics, Condensed Matter, Particle Physics and Fields, Quantum Physics, General Theory of Fields...

Source: http://www.flooved.com/reader/3063

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105

Nov 14, 2013
11/13

by
Ben Simons

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Could formulate many-body propagator (Green function), but here, convenient to focus on partition function.

Topics: Physics, Condensed Matter, Particle Physics and Fields, Quantum Physics, General Theory of Fields...

Source: http://www.flooved.com/reader/3054

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101

Nov 14, 2013
11/13

by
Ben Simons

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In this chapter, the concept of path integration is generalized to integration over quantum �elds. Speci�cally we will develop an approach to quantum �eld theory that takes a sits starting point an integration over all con�gurations of a given �eld, weighted by anappropriate action. To emphasize the importance of the formulation which, methodologiccally, represents the backbone of the remainder of the text, we have pruned the discussion to focus only on the essential elements. This...

Topics: Physics, Condensed Matter, Particle Physics and Fields, Quantum Physics, General Theory of Fields...

Source: http://www.flooved.com/reader/3047

102
102

Nov 14, 2013
11/13

by
Ben Simons

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We have seen that the quantum Heisenberg Ferromagnetic spin chain is characterised by a magnetically ordered ground state with free particle-like elementary spin wave excitations� magnons. What happens in the antiferromagnetic system?

Topics: Physics, Condensed Matter, Particle Physics and Fields, Quantum Physics, General Theory of Fields...

Source: http://www.flooved.com/reader/3068

96
96

Nov 14, 2013
11/13

by
Ben Simons

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We have seen how the elementary excitations of the quantum chain can be presented in terms of new elementary quasi-particles by the ladder operator formalism. Can this approach be generalised to accommodate other many-body systems? The answer is provided by the method of second quantisation � an essential tool for the development of interacting many-body �eld theories. The �rst part of this section is devoted largely to formalism �the second part to applications aimed at developing...

Topics: Physics, Condensed Matter, Particle Physics and Fields, Quantum Physics, General Theory of Fields...

Source: http://www.flooved.com/reader/3064

91
91

Nov 14, 2013
11/13

by
Ben Simons

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Discuss element of PI construction which demands generalisation_ Generalisation of FPI to many-body systems problematic due to particle indistinguishability and statistics. Can second quantisation help? automatically respects particle statistics. Require complete basis on the Fock space to construct PI. Such eigenstates exist and are known as Coherent States

Topics: Physics, Condensed Matter, Particle Physics and Fields, Quantum Physics, General Theory of Fields...

Source: http://www.flooved.com/reader/3053

87
87

Nov 14, 2013
11/13

by
Ben Simons

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Previously, we have seen how the functional �eld integral technique can be developed to explore the impact of the electronic degrees of freedom on the e_ective Coulomb interaction in a metal. However, our considerations did not engage any non-trivial mean-�elds: the platform of the non-interacting electron system remains adiabatically connected to that ofthe weakly interacting system. In the following we will explore a problem in which the development of a non-trivial ground state � the...

Topics: Physics, Condensed Matter, Particle Physics and Fields, Quantum Physics, General Theory of Fields...

Source: http://www.flooved.com/reader/3058

92
92

Nov 14, 2013
11/13

by
Ben Simons

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The aim of this lecture is to explore the nature of the ground state and the character of the elementary excitation spectrum in the condensed phase.

Topics: Physics, Condensed Matter, Particle Physics and Fields, Quantum Physics, General Theory of Fields...

Source: http://www.flooved.com/reader/3069

74
74

Nov 14, 2013
11/13

by
Ben Simons

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So far we have developed an operator-based formulation of many-particle states. However,for this representation to be useful, we have to understand how the action of �rst quantised operators on many-particle states can be formulated within the framework of the second quantisation. To do so, it is natural to look for a formulation in the diagonal basis and recall the action of the particle number operator. To begin, let us consider...

Topics: Physics, Condensed Matter, Particle Physics and Fields, Quantum Physics, General Theory of Fields...

Source: http://www.flooved.com/reader/3065

157
157

Nov 14, 2013
11/13

by
Ben Simons

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The aim of this section is to introduce the language and machinery of classical and quantum �eld theory through its application to the problem of lattice vibrations in a solid. In doing so, we will become acquainted with the notion of symmetry breaking, universality, elementary excitations and collective modes � concepts which will pervade much of thecourse.

Topics: Physics, Condensed Matter, Particle Physics and Fields, Quantum Physics, General Theory of Fields...

Source: http://www.flooved.com/reader/3048

92
92

Nov 14, 2013
11/13

by
Ben Simons

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Previously, we have seen that, when treated in a mean-�eld or saddle-point approximation,the �eld theory of the weakly interacting Bose gas shows a transition to a Bose-Einsteincondensed phase when _ =0where the order parameter, the complex condensate wave-function _0acquires a non-zero expectation value, |_0| = _ ___Ld/g. The spontaneousbreaking of the continuous symmetry associated with the phase of the order parameter isaccompanied by the appearance of massless collective phase...

Topics: Physics, Condensed Matter, Particle Physics and Fields, Quantum Physics, General Theory of Fields...

Source: http://www.flooved.com/reader/3060

91
91

Nov 14, 2013
11/13

by
Ben Simons

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How are the properties of an electron gas in�uenced by weak Coulomb interaction? _ Qualitative considerations: When is the intereaction weak? De�ning

Topics: Physics, Condensed Matter, Particle Physics and Fields, Quantum Physics, General Theory of Fields...

Source: http://www.flooved.com/reader/3056

136
136

Nov 14, 2013
11/13

by
Ben Simons

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How can phenomena of QM tunneling be described by Feynman path integral?

Topics: Physics, Condensed Matter, Particle Physics and Fields, Quantum Physics, General Theory of Fields...

Source: http://www.flooved.com/reader/3052

90
90

Nov 14, 2013
11/13

by
Ben Simons

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Although the second quantisation provides a convenient formulation of many-body systems, it admits solution only for systems that are e_ectively free. In our choice of applications, we were careful to consider only those systems for which interaction e_ects could be considered as small, e.g. large spin in quantum magnetism of weak interaction in the dilute Bose gas. Yet interactions can have a profound e_ect leading to transitions to new phases with elementary excitations very di_erent from the...

Topics: Physics, Condensed Matter, Particle Physics and Fields, Quantum Physics, General Theory of Fields...

Source: http://www.flooved.com/reader/3049

101
101

Nov 14, 2013
11/13

by
Ben Simons

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According to band picture of non-interacting electrons, a 1/2-�lled band of states is metallic. But strong Coulomb interaction of electrons can lead to a condensation or crystallisation of the electron gas into a solid, magnetic, insulating phase � Mott transition. Here we employ the second quantisation to explore the basis of this phenomenon.

Topics: Physics, Condensed Matter, Particle Physics and Fields, Quantum Physics, General Theory of Fields...

Source: http://www.flooved.com/reader/3066

1
1.0

Jun 28, 2018
06/18

by
S. A. Owerre; A. A. Burkov; Roger G. Melko

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We present a large-$S$ study of a quantum spin ice Hamiltonian, introduced by Huang, et al., [PRL 112, 167203 (2014)], on the kagome lattice. This model involves a competition between the frustrating Ising term of classical kagome ice, a Zeeman magnetic field $h$,and a nearest-neighbor transverse spin-flip term $S^x_iS^x_j - S^y_iS^y_j$. Recent Quantum Monte Carlo (QMC) simulations by Carrasquilla, et al., [Nature Communications, 6, 7421, (2015)], uncovered lobes of a disordered phase for large...

Topics: Strongly Correlated Electrons, Condensed Matter

Source: http://arxiv.org/abs/1512.03930

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139

Nov 14, 2013
11/13

by
Ben Simons

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We will learn how elements of perturbation theory can be formulated e_ciently by staying �rmly within the framework of the �eld integral. In doing so, we will see how the �eld integral provides a method for identifying and exploring non-trivial reference ground states � �mean��elds�. A fusion of perturbative and mean��eldmethods will provide us with analytical machinery powerful enough to address a spectrum of rich applications.

Topics: Physics, Condensed Matter, Particle Physics and Fields, Quantum Physics, Statistical Physics and...

Source: http://www.flooved.com/reader/3045

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100

Nov 14, 2013
11/13

by
Ben Simons

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Matsubara Summations Basic idea: by introducing auxiliary function g(z) that has simple poles of strength unity at z = i_n, Cauchy�s theorem implies

Topics: Physics, Condensed Matter, Particle Physics and Fields, Statistical Physics and Thermodynamics,...

Source: http://www.flooved.com/reader/3057

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Jun 29, 2018
06/18

by
Christian Boudreault; S. A. Owerre; M. B. Paranjape

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We consider the one-dimensional spin chain for arbitrary spin $s$ on a periodic chain with $N$ sites, the generalization of the chain that was studied by Blume and Capel \cite{bc}: $$H=\sum_{i=1}^N \left(a (S^z_i)^2+ b S^z_iS^z_{i+1}\right).$$ The Hamiltonian only involves the $z$ component of the spin thus it is essentially an Ising \cite{Ising} model. The Hamiltonian also figures exactly as the anisotropic term in the famous model studied by Haldane \cite{haldane} of the large spin Heisenberg...

Topics: Mathematics, High Energy Physics - Theory, Mathematical Physics, Condensed Matter, Strongly...

Source: http://arxiv.org/abs/1601.06195