Article
Materials Science, Multidisciplinary
H. Y. Yuan, W. P. Sterk, Akashdeep Kamra, Rembert A. Duine
Summary: There has been a recent surge of interest in the quantum properties of magnons for quantum information processing. This study examines the stability of quantum states of magnons against various relaxation and dephasing channels, and identifies two distinct dissipation channels for squeezed magnons. The results provide theoretical tools for studying the decoherence of magnons within a full quantum mechanical framework and further benefit the use of quantum states of magnons for information processing.
Article
Materials Science, Multidisciplinary
Youngmin Lim, Behrouz Khodadadi, Jie-Fang Li, Dwight Viehland, Aurelien Manchon, Satoru Emori
Summary: In this study, the dephasing length of transverse spin current in ferrimagnetic CoGd alloys was estimated, showing that it is about 4-5 times longer in nearly compensated CoGd than in ferromagnetic metals. The finding suggests that antiferromagnetic order can mitigate spin dephasing and that transverse spin current interacts more strongly with the Co sublattice. These results provide fundamental insights into the interplay between spin current and antiferromagnetic order for engineering spin torque effects in ferrimagnetic and antiferromagnetic metals.
Article
Chemistry, Multidisciplinary
Martin Kunth, Leif Schroeder
Summary: The study simplifies the behavior of spin-spin relaxation rates in different chemical environments using hyperpolarized Xe-129 as a reporter ligand. It was found that even in a diamagnetic system, detection of analyte concentrations can be achieved through large Larmor frequency jumps. This approach provides a way to measure exchange rates even in systems where direct measurements are challenging.
Article
Physics, Multidisciplinary
Francesco Carnazza, Federico Carollo, Dominik Zietlow, Sabine Andergassen, Georg Martius, Igor Lesanovsky
Summary: In the study of many-body quantum systems, it is often sufficient to consider the dynamical or stationary properties of local observables. By formulating the problem of finding the generator of the subsystem dynamics as a variational problem and using machine learning techniques, we are able to learn a physically consistent open quantum time-evolution and predict the stationary state of the subsystem dynamics.
NEW JOURNAL OF PHYSICS
(2022)
Article
Astronomy & Astrophysics
Andre Grossardt
Summary: The study presents a detailed derivation of a model to investigate effects of self-gravitation from semi-classical gravity. It suggests that spin interferometry could offer a more accessible route for experimental testing of quantum aspects of gravity compared to previous proposals.
CLASSICAL AND QUANTUM GRAVITY
(2021)
Article
Physics, Multidisciplinary
Ognjen Malkoc, Peter Stano, Daniel Loss
Summary: Theoretically investigating charge-noise-induced spin dephasing of a hole confined in a quasi-two-dimensional silicon quantum dot, the study found that higher-order corrections to the Luttinger Hamiltonian can create "sweet spots" to boost hole-spin dephasing time significantly. The device details, including dot size and asymmetry, growth direction, and applied magnetic and electric fields, play a crucial role in determining the location of these "sweet spots".
PHYSICAL REVIEW LETTERS
(2022)
Article
Physics, Multidisciplinary
Mohamad Toutounji
Summary: Pure electronic dephasing in a mixed quantum-classical environment is investigated using the spin-boson Hamiltonian. Experimental results indicate that electronic dephasing determines the zero-phonon line (ZPL) profile. The contribution of bath modes to pure electronic dephasing is assessed in this study.
PHYSICA A-STATISTICAL MECHANICS AND ITS APPLICATIONS
(2022)
Article
Materials Science, Multidisciplinary
Jia-Xuan Liu, Hai-Long Shi, Yun-Hao Shi, Xiao-Hui Wang, Wen-Li Yang
Summary: The study investigates the relationship between stored energy and entanglement in a central-spin battery, finding an inverse relationship between extractable work and entanglement during the charging process. Utilizing an unpolarized Dicke state as the charger in a central-spin battery shows a significant increase in extractable work and an improvement in charging power proportional to the square root of Nc.
Article
Physics, Multidisciplinary
Mohamad Niknam, Lea F. Santos, David G. Cory
Summary: The research proposes and experimentally measures an entropy that quantifies correlations among qubits in a nearly isolated quantum system. Due to spin-spin interactions, information flows from a central spin to surrounding ones forming clusters of multispin correlations that grow over time. A nuclear magnetic resonance experiment is used to directly measure the amplitudes of multispin correlations and compute the evolution of what is called correlation Renyi entropy, which continues to grow even after the equilibration of entanglement entropy. The study also analyzes how the saturation point and timescale for the equilibration of the correlation Renyi entropy depend on the system size.
PHYSICAL REVIEW LETTERS
(2021)
Article
Materials Science, Multidisciplinary
Claude Dimo, Alexandre Faribault
Summary: Recent research has shown that the XX central spin model is integrable when a magnetic field perpendicular to the coupling plane is present. A large number of its eigenstates exhibit no correlation between the central spin and the spins it is coupled to. In this study, we have demonstrated that the integrability of the XX-central spin model remains even in the presence of a magnetic field oriented arbitrarily. Additionally, we have shown that dark states can still be found in the presence of an in-plane magnetic field if the coupling is strong enough. Finally, we have provided a simple explanation for this result and demonstrated its universality for various distributions of the coupling.
Article
Physics, Multidisciplinary
Yusong Cao, Jian Wang, Yi Qiao, Junpeng Cao, Wen-Li Yang
Summary: This study presents the exact solution of an anisotropic quantum spin chain with various interactions, revealing that NNN couplings can induce off-diagonal boundary reflections which enhance anisotropic interactions on the boundaries and bonds. The system is analytically solved using the off-diagonal Bethe ansatz method, providing insight into inhomogeneous T-Q relations, energy spectra, and Bethe ansatz equations for integrable models with interesting interactions.
JOURNAL OF PHYSICS A-MATHEMATICAL AND THEORETICAL
(2021)
Article
Physics, Fluids & Plasmas
Fei Liu
Summary: By using the probability formulas of quantum trajectories, an auxiliary open quantum system is constructed for a periodically driven open quantum system. It is found that, at a long time limit, the coherent dynamics of the auxiliary system remains the same as that of the original system despite modifications to the Lindblad operators. The construction is illustrated using a periodically driven two-level quantum system.
Article
Optics
Jingyi Fan, Shengshi Pang
Summary: In this work, we investigate the role of finite bath dimension in the Markovianity of quantum dynamics by considering a simple but nontrivial model. We find that the dynamics of the central spin transits from non-Markovian to Markovian as the number of the bath spins increases. The non-Markovianity is characterized by the information backflow from the bath to the system in terms of the trace distance of the system states. We derive the time evolution of the trace distance analytically, and find periodic collapse-revival patterns in the information flow.
Article
Optics
Ludovico Lami, Mark M. Wilde
Summary: This study provides an exact calculation method for the quantum, private, two-way assisted quantum, and secret-key-agreement capacities of all bosonic dephasing channels. The authors prove that these capacities are equal to the relative entropy of the distribution underlying the channel with respect to the uniform distribution.
Article
Optics
Y. Li, Y. Mei, H. Nguyen, P. R. Berman, A. Kuzmich
Summary: Atomic Rydberg interactions allow for the creation of entanglement between atoms and light, which has diverse applications in quantum information science. The interaction-induced dephasing of collective atomic states is often the main contribution to the generation of entanglement in atomic ensembles. Through our study, we elucidate how interaction-induced dephasing is responsible for entanglement generation in many-atom settings.
Article
Physics, Multidisciplinary
Sankar Das Sarma
Summary: Majorana particles, which are the same as their antiparticles, show promise for quantum computing in condensed matter systems. This article discusses the search for Majorana modes in semiconductor heterostructures and the limitations imposed by disorder. Majorana zero modes are emergent phenomena in topological superconductors, and this Perspective provides an overview of their physics, recent experimental progress, and future outlook for success.
Article
Physics, Multidisciplinary
DinhDuy Vu, Sankar Das Sarma
Summary: An ergodic system subjected to an external periodic drive will be heated to infinite temperature, but this heating can be stopped during a prethermal period if the applied frequency is larger than the typical energy scale of the local Hamiltonian. This prethermal period exhibits an emergent symmetry that, if broken, leads to subharmonic oscillation of the discrete time crystal (DTC). The presence of dissipation affects the survival time of the prethermal DTC, with a bath coupling prolonging the prethermal period and interaction with the environment destabilizing spontaneous symmetry breaking, resulting in a nonmonotonic variation of the survival time.
PHYSICAL REVIEW LETTERS
(2023)
Article
Materials Science, Multidisciplinary
Jiabin Yu, Ming Xie, Fengcheng Wu, Sankar Das Sarma
Summary: Signatures of nematic nodal superconductivity have been observed in magic angle twisted bilayer graphene. Researchers propose a general topological mechanism explaining how nematic pairing leads to nodal superconductivity in this material.
Article
Materials Science, Multidisciplinary
Prathyush P. Poduval, Sankar Das Sarma
Summary: We theoretically investigate the issue of doping induced insulator to metal transition in bulk semiconductors by analyzing the density-dependent mean free path and the Anderson localization transition controlled by the Ioffe-Regel-Mott (IRM) criterion. We calculate the mean free path on the highly doped metallic side considering carrier scattering by ionized dopants. The Coulomb disorder of the charged dopants is screened by the carriers themselves, leading to an integral equation for localization. By solving this equation analytically and numerically, we provide detailed results for the critical density of the doping induced metal-insulator transition.
Article
Materials Science, Multidisciplinary
Nathan L. Foulk, Sankar Das Sarma
Summary: We demonstrate the potential realization of quantum Floquet matter, particularly the discrete time crystal (DTC), using modern silicon spin qubits based in quantum dots. This is significant as silicon spin qubits have advantages in dealing with charge noise. We show the differences between prethermal phenomena and true time-crystalline spatiotemporal order, and illustrate rich regime structures in a spin chain of four qubits that are distinct from the thermal regime.
Article
Materials Science, Multidisciplinary
Seth M. Davis, Yang-Zhi Chou, Fengcheng Wu, Sankar Das Sarma
Summary: We calculate the theoretical contribution of scattering by acoustic phonons to the doping and temperature dependence of electrical resistivity in Bernal bilayer graphene (BBG) and rhombohedral trilayer graphene (RTG). The nontrivial geometric features of the band structures of these systems strongly influence the resistivity's temperature and doping dependencies. Our focus on BBG and RTG is motivated by recent experiments in these systems that have discovered exotic low-temperature superconductivity. The understanding of the influence of band geometry on transport is crucial in these systems.
Article
Materials Science, Multidisciplinary
Haining Pan, Sankar Das Sarma
Summary: Motivated by the presence of Majorana zero modes in both the Kitaev chain model and the experimental semiconductor-superconductor Majorana nanowire, this theoretical study investigates the equivalence or similarity between the two models from the perspective of their corresponding dual spin models. By using the Jordan-Wigner transformation, the duality between the Kitaev chain and the transverse-field XY spin model is established, aiming to connect the Kitaev chain and the nanowire. The application of the Jordan-Wigner transformation to the nanowire reveals that the corresponding bosonic spin model is a generalized spin cluster model with staggered couplings. By projecting out the higher energy band of the spinful nanowire system, an effective low-energy spinless system is obtained, leading to the connection between the Kitaev chain and Majorana nanowire.
Article
Materials Science, Multidisciplinary
Yi-Ting Tu, Sankar Das Sarma
Summary: We analyze an experimental work which shows the failure of the Wiedemann-Franz law in graphene at low temperatures, attributing this failure to the non-Fermi liquid nature of the Dirac fluid. Despite theoretical efforts, the observations remain unexplained. Our analysis suggests that the opening of a gap at the Dirac point induced by the substrate may explain the results. Further experiments are needed to resolve the issue and determine the role of electron and hole transport in the presence of disorder and phonons.
Article
Materials Science, Multidisciplinary
Yi-Ting Tu, DinhDuy Vu, S. Das Sarma
Summary: Coupling a one-dimensional quasiperiodic interacting system to a Markovian bath, this study investigates the avalanche instability of the many-body localized phase numerically. The results show that many-body localization (MBL) is more stable in pseudorandom quasiperiodic systems than in randomly disordered systems for a disorder strength W > 8, potentially up to arbitrarily large system sizes. Real-space RG arguments support this conclusion and a detailed comparison between quasiperiodic and random MBL from the avalanche instability perspective reveals that they belong to different universality classes.
Article
Materials Science, Multidisciplinary
Donovan Buterakos, Sankar Das Sarma
Summary: We discuss interesting phenomena in the Hubbard model related to flat-band ferromagnetism. The first is a mathematical theorem that describes the conditions for degeneracy between a flat-band ferromagnetic and a nonferromagnetic state. This theorem is generally applicable and independent of geometry, but only holds for a small number of holes in a filled band. The second phenomenon challenges intuition by showing an example where particles do not prefer to doubly occupy low-energy states before filling higher-energy states. Lastly, we present a pattern of ferromagnetism in small pentagonal and hexagonal plaquettes at specific filling factors. These examples can be observed in quantum dot arrays available in laboratories.
Article
Materials Science, Multidisciplinary
Yi-Hua Lai, Sankar Das Sarma, Jay D. Sau
Summary: Despite recent progress in experimental observations of large zero-bias conductance peaks, it is still unclear whether Majorana modes have been observed. The existing experimental works lack stability of the putative Majorana mode features, indicating the absence of a topological phase. This paper introduces a dimensionless quality factor F to quantify the robustness of the zero-bias conductance peak height and proposes specific experimentally accessible measures for analyzing the stability of the observed peaks. The results show that Majorana modes are significantly more robust compared to nontopological peaks in the low-temperature limit and suggest that the quality factor F can be used to estimate the quality of topological qubits made from Majorana modes.
Article
Materials Science, Multidisciplinary
Jiabin Yu, Yu-An Chen, Sankar Das Sarma
Summary: This study generalizes the topologically obstructed pairings between Chern states by proposing Euler obstructed Cooper pairing in 3D systems. The Euler obstructed pairing widely exists between two Fermi surfaces with nontrivial band topology and can lead to nodal superconductivity and hinge Majorana zero modes under certain conditions.
Article
Materials Science, Multidisciplinary
Yang-Zhi Chou, Fengcheng Wu, Jay D. Sau, Sankar Das Sarma
Summary: This article presents a systematic theory of acoustic-phonon-mediated superconductivity that incorporates Coulomb repulsion and explains recent experiments in Bernal bilayer graphene. The theory predicts that s-wave spin-singlet and f-wave spin-triplet pairings are degenerate and dominant. The results indicate that the observed spin-triplet superconductivity in Bernal bilayer graphene arises from acoustic phonons.
Article
Materials Science, Multidisciplinary
Seongjin Ahn, Sankar Das Sarma
Summary: We developed a minimal theory for the metal-insulator transition observed in two-dimensional moire multilayer transition metal dichalcogenides, attributing it to Coulomb disorder in the environment. Carrier scattering by random charged impurities leads to an effective 2D MIT roughly controlled by the Ioffe-Regel criterion, with necessary random charged impurity content consistent with known levels in TMDs.
Article
Materials Science, Multidisciplinary
Haining Pan, Sankar Das Sarma
Summary: This study theoretically investigates the strong correlation and symmetry breaking behaviors in two-dimensional moire transition metal dichalcogenide bilayers. The dependence of symmetry breaking on the range of electron-electron interaction and temperature is examined, with implications for experimental control and thermal suppression.