Nonequilibrium states of a plasmonic Dicke model with coherent and dissipative surface-plasmon–quantum-emitter interactions
Not Available
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
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Universal finite-time thermodynamics of many-body quantum machines from Kibble-Zurek scaling
We demonstrate the existence of universal features in the finite-time thermodynamics of quantum machines by considering a many-body quantum Otto cycle in which the working medium is driven across quantum critical points during the unitary strokes. Specifically, we consider a quantum engine powered by dissipative energizing and relaxing baths. We show that under very generic conditions, the output work is governed by the Kibble-Zurek mechanism; i.e., it exhibits a universal power-law scaling with the driving speed through the critical points. We also optimize the finite-time thermodynamics as a function of the driving speed. The maximum power and the corresponding efficiency take a universal form, and are reached for an optimal speed that is governed by the critical exponents. We exemplify our results by considering a transverse-field Ising spin chain as the working medium. For this model, we also show how the efficiency and power vary as the engine becomes critical.
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
Nonequilibrium quantum critical steady state: Transport through a dissipative resonant level
Not Available
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
Dynamics and phases of nonunitary Floquet transverse-field Ising model
Inspired by current research on measurement-induced quantum phase transitions, we analyze the nonunitary Floquet transverse-field Ising model with complex nearest-neighbor couplings and complex transverse fields. Unlike its unitary counterpart, the model shows a number of steady phases, stable to integrability-breaking perturbations. Some phases have robust edge modes and/or spatiotemporal long-range orders in the bulk. The transitions between the phases have extensive entanglement entropy, whose scaling with the system size depends on the number of the real quasiparticle modes in the spectrum at the transition. In particular, the volume-law scaling appears on some critical lines, protected by pseudo-Hermiticity. Both the scaling of entanglement entropy in steady states and the evolution after a quench are compatible with the non-Hermitian generalization of the quasiparticle picture of Calabrese and Cardy at least qualitatively. Published by the American Physical Society 2024
Su, Lei (ORCID:0009000455290786)↗
Mapping twist-tuned multiband topology in bilayer WSe 2
Semiconductor moiré superlattices have been shown to host a wide array of interaction-driven ground states. However, twisted homobilayers have been difficult to study in the limit of large moiré wavelengths, where interactions are most dominant. In this study, we conducted local electronic compressibility measurements of twisted bilayer WSe 2 (tWSe 2 ) at small twist angles. We demonstrated multiple topological bands that host a series of Chern insulators at zero magnetic field near a “magic angle” around 1.23°. Using a locally applied electric field, we induced a topological quantum-phase transition at one hole per moiré unit cell. Finally, our work establishes the topological phase diagram of a generalized Kane-Mele-Hubbard model in tWSe 2 , demonstrating a tunable platform for strongly correlated topological phases.
36 MATERIALS SCIENCE↗
Andreev-Majorana bound states in superfluids
We consider Andreev-Majorana (AM) bound states with zero energy on surfaces, interfaces, and vortices in different phases of the p-wave superfluids. We discuss the chiral superfluid {sup 3}He-A and time reversal invariant phases: superfluid {sup 3}He-B, planar and polar phases. The AM zero modes are determined by topology in the bulk and disappear at the quantum phase transition from the topological to nontopological state of the superfluid. The topology demonstrates the interplay of dimensions. In particular, the zero-dimensional Weyl points in chiral superfluids (the Berry phase monopoles in momentum space) give rise to the one-dimensional Fermi arc of AM bound states on the surface and to the one-dimensional flat band of AM modes in the vortex core. The one-dimensional nodal line in the polar phase produces a two-dimensional flat band of AM modes on the surface. The interplay of dimensions also connects the AM states in superfluids with different dimensions. For example, the topological properties of the spectrum of bound states in three-dimensional {sup 3}He-B are connected to the properties of the spectrum in the two-dimensional planar phase (thin film)
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Quasiparticles of strongly correlated Fermi liquids at high temperatures and in high magnetic fields
Strongly correlated Fermi systems are among the most intriguing, best experimentally studied and fundamental systems in physics. There is, however, lack of theoretical understanding in this field of physics. The ideas based on the concepts like Kondo lattice and involving quantum and thermal fluctuations at a quantum critical point have been used to explain the unusual physics. Alas, being suggested to describe one property, these approaches fail to explain the others. This means a real crisis in theory suggesting that there is a hidden fundamental law of nature. It turns out that the hidden fundamental law is well forgotten old one directly related to the Landau-Migdal quasiparticles, while the basic properties and the scaling behavior of the strongly correlated systems can be described within the framework of the fermion condensation quantum phase transition (FCQPT). The phase transition comprises the extended quasiparticle paradigm that allows us to explain the non-Fermi liquid (NFL) behavior observed in these systems. In contrast to the Landau paradigm stating that the quasiparticle effective mass is a constant, the effective mass of new quasiparticles strongly depends on temperature, magnetic field, pressure, and other parameters. Our observations are in good agreement with experimental facts and show that FCQPT is responsible for the observed NFL behavior and quasiparticles survive both high temperatures and high magnetic fields.
73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
Anisotropy of the Hall Effect in a Quasi-Two-Dimensional Electron-Doped Nd{sub 2 –} {sub x}Ce{sub x}CuO{sub 4 + δ} Superconductor
Abstract—The temperature dependences of the Hall effect of an electron-doped Nd{sub 2 –} {sub x}Ce{sub x}CuO{sub 4 + δ} superconductor have been studied at the antiferromagnet–superconductor quantum phase transition boundary (0.135 ≤ x ≤ 0.15) in conducting CuO{sub 2} planes and in the direction perpendicular to the CuO{sub 2} plane. The hall coefficient between the conducting planes has been found be two orders higher than that in the conducting planes over entire temperature range, which is due to the incoherent character of the charge carrier transfer in the direction of axis c.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
ANDES (ARGONNE NUCLEAR DATA EXPLORATION SOFTWARE) - ndviz
The Argonne Nuclear Data Exploration Software (ANDES) is a collection of open-source C++ codes and ROOT scripts that enable the visualization of patterns emerging from nuclear data. From this global view, well-known phenomena such as major nuclear shell closures and pairing effects near N=Z nuclei, as well as more subtle features, such as quantum phase transition around the Zr isotopes or the charge radius staggering in the Hg isotopes, can be observed. This visualization tool apart from having pedagogic application can serve as a tool for discovering previously unknown phenomena in the nuclear chart.
Santiago-Gonzalez, Daniel↗
ANDES (ARGONNE NUCLEAR DATA EXPLORATION SOFTWARE) - Physics Tools
A collection of physics tools used by the ANDES. The Argonne Nuclear Data Exploration Software (ANDES) is a collection of open-source C++ codes and ROOT scripts that enable the visualization of patterns emerging from nuclear data. From this global view, well-known phenomena such as major nuclear shell closures and pairing effects near N=Z nuclei, as well as more subtle features, such as quantum phase transition around the Zr isotopes or the charge radius staggering in the Hg isotopes, can be observed. This visualization tool apart from having pedagogic application can serve as a tool for discovering previously unknown phenomena in the nuclear chart.
Santiago-Gonzalez, Daniel↗
Nature of the zero-bias conductance peak associated with Majorana bound states in topological phases of semiconductor-superconductor hybrid structures
Rashba spin-orbit coupled semiconductor-superconductor hybrid structures in the presence of Zeeman splitting have emerged as the first experimentally realizable topological superconductor supporting zero-energy Majorana bound states. However, recent experimental studies in these hybrid structures are not in complete agreement with the theoretical predictions, for example, the observed height of the zero-bias conductance peak (ZBCP) associated with the Majorana bound states is less than 10% of the predicted quantized value 2e 2 /h. We try to understand the sources of various discrepancies between the recent experiments and the earlier theories by starting from a microscopic theory and studying non-equilibrium transport in these systems at arbitrary temperatures and applied bias voltages. Our approach involves quantum Langevin equations and non-equilibrium Green’s functions. Here we are able to model the tunnel coupling between the one-dimensional semiconductor-superconductor hybrid structure and the metallic leads realistically; study the role of tunnel coupling on the height of the ZBCP and the subgap conductance; predict the nature of the splitting of the ZBCP with an increasing magnetic field beyond the critical field; show the behavior of the ZBCP with an increasing gate-controlled onsite potential; and study the evolution of the full differential conductance across the topological quantum phase transition. When the applied magnetic field is quite large compared to the Rashba splitting and the bulk energy gap is much reduced, we find the ZBCP even for an onsite potential much larger than the applied magnetic field. The height of the corresponding ZBCP depends on the tunnel coupling even at zero temperature and can be much smaller than 2e 2 /h.
36 MATERIALS SCIENCE↗
Final Technical Report - DOE Grant No. DE-FG02-07ER46424
We present a final report on the activities undertaken under DOE Grant No. DE-FG02-07ER46424, titled "Interaction effects in quasi one-dimensional electronic systems," originally under the direction of Prof. Julia Meyer. The report includes an overview of the grant and the personnel involved, a list of publications acknowledging the grant, and a summary of the results and conclusions drawn from research supported by the grant.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Theoretical Research at the High Energy Frontier: Cosmology and Beyond
During the one year term of this DOE award, Vachaspati has continued to work on the interface of particle physics and cosmology, with a focus on primordial magnetic fields, cosmic phase transitions, quantum mechanical effects on classical dynamics, and black hole formation.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Emergent phases in iron pnictides: Double-Q antiferromagnetism, charge order and enhanced nematic correlations
Electron correlations produce a rich phase diagram in the iron pnictides. Earlier theoretical studies on the correlation effect demonstrated how quantum fluctuations weaken and concurrently suppress a $C_2$-symmetric single-Q antiferromagnetic order and a nematic order. Here we examine the emergent phases near the quantum phase transition. For a $C_4$-symmetric collinear double-Q antiferromagnetic order, we show that it is accompanied by both a charge order and an enhanced nematic susceptibility. Our results provide understanding for several intriguing recent experiments in hole-doped iron arsenides, and bring out common physics that underlies the different magnetic phases of various iron-based superconductors.
Yu, R↗
Integer versus half-integer spin on an approximate honeycomb lattice
Recent interest in honeycomb lattice materials has focused on their potential to host quantum spin liquid (QSL) states. Variations in bond angles and spin allow a range of interesting behaviors on this lattice, from the predicted QSL ground state of the Kitaev model to exotic magnetic orders. Here we report the physical properties of two compounds with rare earths on an approximate honeycomb lattice. Here, the isostructural compounds Nd 2 S 5 Sn (J = 9/2) and Pr 2 S 5 Sn (J = 4) permit a direct comparison of half-integer versus integer spins on this lattice. We find strikingly different magnetic properties for the two compounds. Nd 2 S 5 Sn orders antiferromagnetically at T N ≈ 2.5 K and undergoes several magnetic transitions to other ordered states under applied field. Pr 2 S 5 Sn displays no magnetic ordering transition above T = 0.41 K, and may be proximate to a spin liquid state.
36 MATERIALS SCIENCE↗
Quantum computation of phase transition in the massive Schwinger model
Abstract As pointed out by Coleman, physical quantities in the Schwinger model depend on a parameter θ that determines the background electric field. There is a phase transition for θ = π only. We develop a momentum space formalism on a lattice and use it to perform a quantum computation of the critical point of this phase transition on the NISQ device IMB Q Lima. After error mitigation, our results give strong indication of the existence of a critical point at m / e ≃ 0.32, where m is the bare fermion mass and e is the coupling strength, in good agreement with the classical numerical result m / e ≃ 0.3335.
Physics↗
Finite-Time Teleportation Phase Transition in Random Quantum Circuits
How long does it take to entangle two distant qubits in a quantum circuit evolved by generic unitary dynamics? Here, we show that if the time evolution is followed by measurements of all but two infinitely separated test qubits, then the entanglement between them can undergo a phase transition and become nonzero at a finite critical time t c . The fidelity of teleporting a quantum state from an input qubit to an infinitely distant output qubit shows the same critical onset. Specifically, these finite-time transitions occur in short-range interacting two-dimensional random unitary circuits and in sufficiently long-range interacting one-dimensional circuits. The phase transition is understood by mapping the random continuous-time evolution to a finite-temperature thermal state of an effective spin Hamiltonian, where the inverse temperature equals the evolution time in the circuit. In this framework, the entanglement between two distant qubits at times t > t c corresponds to the emergence of long-range ferromagnetic spin correlations below the critical temperature. We verify these predictions using numerical simulation of Clifford circuits and propose potential realizations in existing platforms for quantum simulation.
36 MATERIALS SCIENCE↗
Dielectric Relaxation by Quantum Critical Magnons
We report the experimental observation of dielectric relaxation by quantum critical magnons. Complex capacitance measurements reveal a dissipative feature with a temperature-dependent amplitude due to low-energy lattice excitations and an activation behavior of the relaxation time. The activation energy softens close to a field-tuned magnetic quantum critical point at H = H c and follows single-magnon energy for H > H c , showing its magnetic origin. Furthermore, our study demonstrates the electrical activity of coupled low-energy spin and lattice excitations, an example of quantum multiferroic behavior.
1-dimensional spin chains↗