5
5.0

Jun 26, 2018
06/18

by
M. Brando; D. Belitz; F. M. Grosche; T. R. Kirkpatrick

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This review gives an overview of the quantum phase transition (QPT) problem in metallic ferromagnets, discussing both experimental and theoretical aspects. These QPTs can be classified with respect to the presence and strength of quenched disorder: Clean systems generically show a discontinuous, or first-order, QPT from the ferromagnetic state to a paramagnetic one as a function of some control parameter, as predicted by theory. Disordered systems are much more complicated, depending on the...

Topics: Strongly Correlated Electrons, Condensed Matter

Source: http://arxiv.org/abs/1502.02898

1
1.0

Jun 27, 2018
06/18

by
V. Janiš; J. Kolorenč

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We scrutinize the diagrammatic perturbation theory of noninteracting electrons in a random potential with the aim to accomplish a consistent comprehensive theory of quantum diffusion. Ward identity between the one-electron self-energy and the two-particle irreducible vertex is generally not guaranteed in the perturbation theory with only elastic scatterings. We show how the Ward identity can be established in practical approximations and how the functions from the perturbation expansion should...

Topics: Condensed Matter, Disordered Systems and Neural Networks

Source: http://arxiv.org/abs/1504.05504

6
6.0

Jun 28, 2018
06/18

by
D. S. Lobser; A. E. S. Barentine; E. A. Cornell; H. J. Lewandowski

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Well before the atomistic nature of matter was experimentally established, Ludwig Boltzmann's audacious effort to explain the macroscopic world of human experience in terms of the workings of an unseen microscopic world met with vigorous opposition. A contentious point was the problem of irreversibility: the microscopic equations of motion are reversible, yet friction and viscosity cause things always to slow down and warm up, never to speed up and cool down. What was worse, Boltzmann himself...

Topics: Physics, Atomic Physics, Quantum Gases, Condensed Matter

Source: http://arxiv.org/abs/1509.00366

3
3.0

Jun 26, 2018
06/18

by
Filippo Bovo

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Standard derivations of the functional integral in non-equilibrium quantum field theory are based on the discrete time representation. In this work we derive the non-equilibrium functional integral for non-interacting bosons and fermions using a continuum time approach by accounting for the statistical distribution through the boundary conditions and using them to evaluate the Green's function.

Topics: Statistical Mechanics, Mathematics, Mathematical Physics, Condensed Matter

Source: http://arxiv.org/abs/1502.07630

2
2.0

Jun 28, 2018
06/18

by
Davide Cadeddu; Jean Teissier; Floris Braakman; Niels Gregersen; Petr Stepanov; Jean-Michel Gérard; Julien Claudon; Richard J. Warburton; Martino Poggio; Mathieu Munsch

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We present the experimental realization of a quantum fiber-pigtail. The device consists of a semiconductor quantum-dot embedded into a conical photonic wire that is directly connected to the core of a fiber-pigtail. We demonstrate a photon collection efficiency at the output of the fiber of 5.8% and suggest realistic improvements for the implementation of a useful device in the context of quantum information. We finally discuss potential applications in scanning probe microscopy.

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

Source: http://arxiv.org/abs/1506.06635

6
6.0

Jun 27, 2018
06/18

by
Peter Lunts; Subhro Bhattacharjee; Jonah Miller; Erik Schnetter; Yong Baek Kim; Sung-Sik Lee

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We apply the quantum renormalization group to construct a holographic dual for the U(N) vector model for complex bosons defined on a lattice. The bulk geometry becomes dynamical as the hopping amplitudes which determine connectivity of space are promoted to quantum variables. In the large N limit, the full bulk equations of motion for the dynamical hopping fields are numerically solved for finite systems. From finite size scaling, we show that different phases exhibit distinct geometric...

Topics: Condensed Matter, Strongly Correlated Electrons, High Energy Physics - Theory

Source: http://arxiv.org/abs/1503.06474

6
6.0

Jun 28, 2018
06/18

by
Yutaka Tabuchi; Seiichiro Ishino; Atsushi Noguchi; Toyofumi Ishikawa; Rekishu Yamazaki; Koji Usami; Yasunobu Nakamura

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The techniques of microwave quantum optics are applied to collective spin excitations in a macroscopic sphere of ferromagnetic insulator. We demonstrate, in the single-magnon limit, strong coupling between a magnetostatic mode in the sphere and a microwave cavity mode. Moreover, we introduce a superconducting qubit in the cavity and couple the qubit with the magnon excitation via the virtual photon excitation. We observe the magnon-vacuum-induced Rabi splitting. The hybrid quantum system...

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

Source: http://arxiv.org/abs/1508.05290