| 471. |
- Alkurtass, B., et al.
(författare)
-
Entanglement structure of the two-channel Kondo model
- 2016
-
Ingår i: Physical Review B. - 2469-9950. ; 93:8
-
Tidskriftsartikel (refereegranskat)abstract
- Two electronic channels competing to screen a single impurity spin, as in the two-channel Kondo model, are expected to generate a ground state with a nontrivial entanglement structure. We exploit a spin-chain representation of the two-channel Kondo model to probe the ground-state block entropy, negativity, tangle, and Schmidt gap, using a density matrix renormalization group approach. In the presence of symmetric coupling to the two channels, we confirm field-theory predictions for the boundary entropy difference ln(g(UV)/g(IR)) = ln(2)/2 between the ultraviolet and infrared limits and the leading ln(x)/x impurity correction to the block entropy. The impurity entanglement S-imp is shown to scale with the characteristic length xi(2CK). We show that both the Schmidt gap and the entanglement of the impurity with one of the channels-as measured by the negativity-faithfully serve as order parameters for the impurity quantum phase transition appearing as a function of channel asymmetry, allowing for explicit determination of critical exponents, nu approximate to 2 and beta approximate to 0.2. Remarkably, we find the emergence of tripartite entanglement only in the vicinity of the critical channel-symmetric point.
|
|
| 472. |
- Bayat, A., et al.
(författare)
-
Entanglement Probe of Two-Impurity Kondo Physics in a Spin Chain
- 2012
-
Ingår i: Physical Review Letters. - 0031-9007. ; 109:6
-
Tidskriftsartikel (refereegranskat)abstract
- We propose that real-space properties of the two-impurity Kondo model can be obtained from an effective spin model where two single-impurity Kondo spin chains are joined via an Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction between the two impurity spins. We then use a density matrix renormalization group approach, valid in all ranges of parameters, to study its features using two complementary quantum-entanglement measures, the negativity and the von Neumann entropy. This nonperturbative approach enables us to uncover the precise dependence of the spatial extent xi(K) of the Kondo screening cloud with the Kondo and RKKY couplings. Our results reveal an exponential suppression of the Kondo temperature T-K similar to 1/xi(K) with the size of the effective impurity spin in the limit of large ferromagnetic RKKY coupling, a striking display of "Kondo resonance narrowing" in the two-impurity Kondo model. We also show how the antiferromagnetic RKKY interaction produces an effective decoupling of the impurities from the bulk already for intermediate strengths of this interaction, and, furthermore, exhibit how the non-Fermi liquid quantum critical point is signaled in the quantum entanglement between various parts of the system.
|
|
| 473. |
- Bayat, A., et al.
(författare)
-
Measurement Quench in Many-Body Systems
- 2018
-
Ingår i: Physical Review Letters. - 0031-9007. ; 121:3
-
Tidskriftsartikel (refereegranskat)abstract
- Measurement is one of the key concepts which discriminates classical and quantum physics. Unlike classical systems, a measurement on a quantum system typically alters it drastically as a result of wave function collapse. Here we suggest that this feature can be exploited for inducing quench dynamics in a many-body system while leaving its Hamiltonian unchanged. Importantly, by doing away with dedicated macroscopic devices for inducing a quench-using instead the indispensable measurement apparatus only-the protocol is expected to be easier to implement and more resilient against decoherence. By way of various case studies, we show that our scheme also has decisive advantages beyond reducing decoherence-for spectroscopy purposes and probing nonequilibrium scaling of critical and quantum impurity many-body systems.
|
|
| 474. |
- Bayat, A., et al.
(författare)
-
Nonequilibrium critical scaling in quantum thermodynamics
- 2016
-
Ingår i: Physical Review B. - 2469-9950. ; 93:20
-
Tidskriftsartikel (refereegranskat)abstract
- The emerging field of quantum thermodynamics is contributing important results and insights into archetypal many-body problems, including quantum phase transitions. Still, the question whether out-of-equilibrium quantities, such as fluctuations of work, exhibit critical scaling after a sudden quench in a closed system has remained elusive. Here, we take a novel approach to the problem by studying a quench across an impurity quantum critical point. By performing density matrix renormalization group computations on the two-impurity Kondo model, we are able to establish that the irreversible work produced in a quench exhibits finite-size scaling at quantum criticality. This scaling faithfully predicts the equilibrium critical exponents for the crossover length and the order parameter of the model, and, moreover, implies an exponent for the rescaled irreversible work. By connecting the irreversible work to the two-impurity spin correlation function, our findings can be tested experimentally.
|
|
| 475. |
- Bayat, A., et al.
(författare)
-
Quantum thermodynamics at impurity quantum phase transitions
- 2020
-
Ingår i: Springer Proceedings in Physics. - Cham : Springer International Publishing. - 0930-8989. ; 239, s. 361-373
-
Tidskriftsartikel (refereegranskat)abstract
- The study of quantum thermodynamics, i.e. equilibrium and non-equilibrium thermodynamics of quantum systems, has been applied to various many-body problems, including quantum phase transitions. An important question is whether out-of-equilibrium quantities from this emerging field, such as fluctuations of work, exhibit scaling after a sudden quench. In particular, it is very interesting to explore this problem in impurity models where the lack of an obvious symmetry breaking at criticality makes it very challenging to characterize. Here, by considering a spin emulation of the two impurity Kondo model and performing density matrix renormalization group computations, we establish that the irreversible work produced in a quench exhibits finite-size scaling at quantum criticality. Our approach predicts the equilibrium critical exponents for the crossover length and the order parameter of the model, and, moreover, implies a new exponent for the rescaled irreversible work. © Springer Nature Switzerland AG 2020.
|
|
| 476. |
- Bayat, A., et al.
(författare)
-
Universal single-frequency oscillations in a quantum impurity system after a local quench
- 2015
-
Ingår i: Physical Review B. - 1098-0121. ; 92:15
-
Tidskriftsartikel (refereegranskat)abstract
- Universal single-frequency oscillations in the local nonequilibrium dynamics of a quantum many-body system are an exceptional phenomenon. In fact, till now, this has never been observed or predicted for the physically relevant case where a system is prepared to be quenched from one quantum phase to another. Here we show how the quench dynamics of the entanglement spectrum may reveal the emergence of such oscillations in a correlated quantum system with Kondo impurities. The oscillations we find are characterized by a single frequency. This frequency is independent of the amount of energy released by the local quench, and scales with the inverse system size. Importantly, the quench-independent frequency manifests itself also in local observables, such as the spin-spin correlation function of the impurities.
|
|
| 477. |
|
|
| 478. |
- Bose, A., et al.
(författare)
-
Hybrid renewable power systems for generation of own power by small and medium-scale enterprises
- 2018
-
Ingår i: E3S Web of Conferences. - : EDP Sciences. - 2267-1242.
-
Konferensbidrag (refereegranskat)abstract
- Decentralized power generation, from renewables, is an attractive option for the future energy transition. Through a case study, the techno-economic feasibility to produce own power from distributed renewable to de-carbonize the operations of the Small and Medium Scale Enterprises (SMEs) was critically analysed. The case study was performed on one of the leading printing outfits of Sri Lanka. Solar photovoltaic (PV) and biomass gasification systems are the most cost-efficient and easy to operate technologies for grid-connected, small-scale power generation, at present, for the context. Grid integration has been found as a major challenge, in both technical and economic parameters of the project. The low capacity factor of solar PV and complexity of the supply chain for biomass power systems are critical to the respective technologies. A hybrid Solar PV-Biomass gasification power plant would have superior techno-economic performances with lower environmental impact than stand-alone systems. An equal share of the net power capacity between the technologies was obtained as the most suitable combination for the proposed hybrid power plant. A net carbon dioxide reduction of more than eighty percent of the operations of the SMEs is feasible. Socio-political factors also have a high impact on overall viability of such small-scale systems.
|
|
| 479. |
|
|
| 480. |
|
|
