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Articles 1 - 6 of 6
Full-Text Articles in Physics
Contact In The Unitary Fermi Gas Across The Superfluid Phase Transition, S. Jensen, Christopher N. Gilbreth, Y. Alhassid
Contact In The Unitary Fermi Gas Across The Superfluid Phase Transition, S. Jensen, Christopher N. Gilbreth, Y. Alhassid
All Faculty Scholarship for the College of the Sciences
A quantity known as the contact is a fundamental thermodynamic property of quantum many-body systems with short-range interactions. Determination of the temperature dependence of the contact for the unitary Fermi gas of infinite scattering length has been a major challenge, with different calculations yielding qualitatively different results. Here we use finite-temperature auxiliary-field quantum Monte Carlo (AFMC) methods on the lattice within the canonical ensemble to calculate the temperature dependence of the contact for the homogeneous spin-balanced unitary Fermi gas. We extrapolate to the continuum limit for 40, 66, and 114 particles, eliminating systematic errors due to finite-range effects. We observe …
Metastable States In Classical And Quantum Systems, Mark Makela, Samantha Parmley, Roger Yu
Metastable States In Classical And Quantum Systems, Mark Makela, Samantha Parmley, Roger Yu
All Faculty Scholarship for the College of the Sciences
The classical vibrational metastable states in a one-dimensional two-mass system are investigated experimentally and theoretically via the transmission of a coherent wave packet propagating through the system. The Fourier transform of the vibrational signal recorded in between the masses reveals resonant excitations by the coherent wave packet. The time-resolved spectrum indicates that the lifetime of a metastable state of higher frequency is longer than that of lower frequency, which is in contrast with the quantum mechanical double-barrier system. This study, which is easily accessible to physics majors, also demonstrates quantum resonant tunneling in a very simple classical way.
Vibrational Properties Of A Loaded String, Samantha Parmley, Tom Zobrist, Terry Clough, Anthony Perez-Miller, Mark Makela
Vibrational Properties Of A Loaded String, Samantha Parmley, Tom Zobrist, Terry Clough, Anthony Perez-Miller, Mark Makela
All Faculty Scholarship for the College of the Sciences
In this paper we discuss our study of a string–mass chain and its anology to quantum mechanical systems. Theoretical predictions are made based upon the numerical solution to the wave equation. These predictions are tested experimentally using both normal mode analysis and pulse analysis. The frequency band structures for periodic and disordered string mass chains are studied as well as their corresponding eigenfunctions. The theoretical and experimental results are in accord. This experiment, suitable for advanced physics majors, demonstrates many important features of quantum mechanics: eigenvalues, superposition principle, band structure, gap modes, and Anderson localization.
Wannier-Stark Localization In Modulation-Doped Multiple-Quantum-Well Structures, Roger H. Yu
Wannier-Stark Localization In Modulation-Doped Multiple-Quantum-Well Structures, Roger H. Yu
All Faculty Scholarship for the College of the Sciences
The external-electric-field effect and the doping effect on a modulation-doped finite-length GaAs/AlxGa1−xAs superlattice have been studied by solving the Schrödinger-Kohn-Sham equation and the Poisson equation self-consistently. In the heavy-doping case, the external electric field makes electrons sequentially tunnel through several potential barriers, and accumulates electrons near one side of the finite-length superlattice. The collective motion of the electrons results in high- and low-field domains in the superlattice. We have found that Wannier-Stark localization exists only in the high-field domain, and that the electronic states are not evenly spaced. The electric-field-induced (doping induced) depopulation (population) of subbands …
Self-Consistent Determination Of Electronic Structure And Elementary Excitations Of Finite Modulation-Doped Superlattices, Roger H. Yu
All Faculty Scholarship for the College of the Sciences
A self-consistent framework for the study of the electronic level structure of finite superlattices has been proposed. One of the surface states (Tamm states) found in our calculation crosses the Fermi energy in the energy gap when the depletion effect near the surface increases. We have shown the existence of low-energy Tamm states in our calculation when the surface barrier is lower than that of the interior. The electronic excitations of the superlattice have been studied via the electron-energy-loss function within the random-phase approximation. Two plasmon modes (well above the phonon response frequency) due to the Tamm states have also …
Tamm States In Finite Semiconductor Superlattices: Influence Of Accumulation And Depletion Layers, Roger H. Yu
Tamm States In Finite Semiconductor Superlattices: Influence Of Accumulation And Depletion Layers, Roger H. Yu
All Faculty Scholarship for the College of the Sciences
We discuss the electronic-level structure of finite semiconductor superlattices and the influence of accumulation and depletion regions on the surface localized states (Tamm states). Exact solutions of the Poisson and Schrödinger equations are obtained self-consistently, through use of a nonuniform jellium model. Both high-energy and low-energy Tamm states are found.