Sr isotopes: the interplay between shape coexistence and quantum phase transitions

In this contribution we study the even-even Sr isotopes considering the influence of particle-hole intruder states. We find that the rapid onset of deformation at A $=98$ and onwards can be explained by the crossing of regular and intruder states. We compare the systematics of Sr with the ones of Zr, Pt, and Hg nucleiComment: To appear in the EUNPC 2022 proceeding

Number conserving particle-hole RPA for superfluid nuclei

TheAuthor(s) - .Published by Elsevier B.V. "This is an open access article under the CCBY license (http://creativecommons.org/licenses/by/4.0/).Funded by SCOAP"We present a number conserving particle-hole RPA theory for collective excitations in the transition from normal to superfluid nuclei. The method derives from an RPA theory developed long ago in quantum chemistry using antisymmetric geminal powers, or equivalently number projected HFB states, as reference states. We show within a minimal model of pairing plus monopole interactions that the number conserving particle-hole RPA excitations evolve smoothly across the superfluid phase transition close to the exact results, contrary to particle-hole RPA in the normal phase and quasiparticle RPA in the superfluid phase that require a change of basis at the broken symmetry point. The new formalism can be applied in a straightforward manner to study particle-hole excitations on top of a number projected HFB state.Consejería de Economía, Conocimiento, Empresas y Universidad de la Junta de Andalucía (Spain) FQM-160 and FQM-370Fondo Europeo de Desarrollo Regional (ERDF), ref. SOMM17/6105/UGRMinisterio de Ciencia, Innovación y Universidades and the ERDF under Projects No. FIS2015-63770-P, FIS2017-88410-P and PGC2018-094180-B-I00CEAFMC and Universidad de Huelva High Performance Computer (HPC@UHU) funded by FEDER/MINECO project UNHU-15CE-284

Number conserving particle-hole RPA for superfluid nuclei

TheAuthor(s) - .Published by Elsevier B.V. "This is an open access article under the CCBY license (http://creativecommons.org/licenses/by/4.0/).Funded by SCOAP"We present a number conserving particle-hole RPA theory for collective excitations in the transition from normal to superfluid nuclei. The method derives from an RPA theory developed long ago in quantum chemistry using antisymmetric geminal powers, or equivalently number projected HFB states, as reference states. We show within a minimal model of pairing plus monopole interactions that the number conserving particle-hole RPA excitations evolve smoothly across the superfluid phase transition close to the exact results, contrary to particle-hole RPA in the normal phase and quasiparticle RPA in the superfluid phase that require a change of basis at the broken symmetry point. The new formalism can be applied in a straightforward manner to study particle-hole excitations on top of a number projected HFB state.Consejería de Economía, Conocimiento, Empresas y Universidad de la Junta de Andalucía (Spain) FQM-160 and FQM-370Fondo Europeo de Desarrollo Regional (ERDF), ref. SOMM17/6105/UGRMinisterio de Ciencia, Innovación y Universidades and the ERDF under Projects No. FIS2015-63770-P, FIS2017-88410-P and PGC2018-094180-B-I00CEAFMC and Universidad de Huelva High Performance Computer (HPC@UHU) funded by FEDER/MINECO project UNHU-15CE-284

Connection between decoherence and excited state quantum phase transitions

In this work we explore the relationship between an excited state quantum phase transition (ESQPT) and the phenomenon of quantum decoherence. For this purpose, we study how the decoherence is affected by the presence of a continuous ESQPT in the environment. This one is modeled as a two level boson system described by a Lipkin Hamiltonian. We will show that the decoherence of the system is maximal when the environment undergoes a continuous ESQPT

Quantum phase transitions in atomic nuclei

Seminario impartido en el workshop organizado por el Instituto Carlos I de la Universidad de Granada en marzo de 2018.Quantum phase transitions in atomic nucle

Nuclear Physics at the border: shape coexistence and quantum phase transitions

Seminario impartido en en la universidad de Faro en el marco de proyecto "Impulso transfronterizo a la investigación en física teórica, subatómica y molecular entre las universidades del Algarve, Huelva y Sevilla." marzo de 2018.Nuclear Physics at the border: shape coexistence and quantum phase transition

The phase diagram of the (extended) Agassi model

Seminario impartido en el workshop "Quantum Phase Transitions Barcelona", 5-6 April 2018The phase diagram of the (extended) Agassi mode

Exceptional spectral phase in a dissipative collective spin model

We study a model of a quantum collective spin weakly coupled to a spin-polarized Markovian environment and find that the spectrum is divided into two regions that we name normal and exceptional Liouvillian spectral phases. In the thermodynamic limit, the exceptional spectral phase displays the unique property of being made up exclusively of second-order exceptional points. As a consequence, the evolution of any initial density matrix populating this region is slowed down and cannot be described by a linear combination of exponential decays. This phase is separated from the normal one by a critical line in which the density of Liouvillian eigenvalues diverges, a phenomenon analogous to that of excited-state quantum phase transitions observed in some closed quantum systems. In the limit of no bath polarization, this criticality is transferred onto the steady state, implying a dissipative quantum phase transition and the formation of a boundary time crystal.MCIN/AEI PGC2018-094180-B-I00 PID2019-104002GB-C21European CommissionCAM/FEDER Project S2018/TCS-4342Junta de Andalucia UHU-1262561 P20-00764CSIC Research Platform on Quantum Technologies PTI-001La Caixa Foundation 100010434 LCF/BQ/DR21/1188002

A digital quantum simulation of the Agassi model

This work was partially supported by the Consejería de Trans-formación Económica, Industria, Conocimiento y Universidades de la Junta de Andalucía (Spain) and ERDF under Groups FQM-160, FQM-177, and FQM-370, and under projects P20-00617, P20-00764, P20-01247, UHU-1262561, and US-1380840; by grants PGC2018-095113-B-I00, PID2019-104002GB-C21, PID2019-104002GB-C22, and PID2020-114687GB-I00 funded by MCIN/AEI/10.13039/50110001103 and “ERDF A way of making Europe” and by ERDF, ref. SOMM17/6105/UGR. Resources supporting this work were pro-vided by the CEAFMC and Universidad de Huelva High Performance Computer (HPC@UHU) funded by ERDF/MINECO project UNHU-15CE-2848.A digital quantum simulation of the Agassi model from nuclear physics is proposed and analyzed. The proposal is worked out for the case with four different sites. Numerical simulations and analytical estimations are presented to illustrate the feasibility of this proposal with current technology. The proposed approach is fully scalable to a larger number of sites. The use of a quantum correlation function as a probe to explore the quantum phases by quantum simulating the time dynamics, with no need of computing the ground state, is also studied. Evidence is given showing that the amplitude of the time dynamics of a correlation function in this quantum simulation is linked to the different quantum phases of the system. This approach establishes an avenue for the digital quantum simulation of useful models in nuclear physics.Consejería de Trans-formación Económica, Industria, Conocimiento y Universidades de la Junta de Andalucía (Spain) and ERDF under Groups FQM-160, FQM-177, and FQM-370, and under projects P20-00617, P20-00764, P20-01247, UHU-1262561, and US-1380840PGC2018-095113-B-I00, PID2019-104002GB-C21, PID2019-104002GB-C22, and PID2020-114687GB-I00 funded by MCIN/AEI/10.13039/50110001103“ERDF A way of making Europe” and by ERDF, ref. SOMM17/6105/UGRCEAFMCUniversidad de Huelva High Performance Computer (HPC@UHU) funded by ERDF/MINECO project UNHU-15CE-284

Simultaneous γ-ray and electron spectroscopy of 182,184,186 Hg isotopes

We would like to thank Tibor Kibédi for fruitful discussions regarding internal conversion coefficients. We acknowledge the support of the ISOLDE Collaboration and technical teams. This project has received funding from the European Union's Horizon 2020 research and innovation programme Grant Agreements No. 654002 (ENSAR2), 665779, and 771036 (CoG MAIDEN). T.R.R. acknowledges the computing resources and assistance provided by GSI-Darmstadt and CCC-UAM. This work has been funded by FWO-Vlaanderen (Belgium), by GOA/2015/010 (BOF KU Leuven), by the Interuniversity Attraction Poles Programme initiated by the Belgian Science Policy Office (BriX network P7/12), by the Slovak Research and Development Agency (Contract No. APVV-18-0268), by the Slovak Grant Agency VEGA (Contract No. 1/0651/21), by Spanish Grants No. FPA2015-64969-P, FPA2015-65035-P, FPA2017-87568-P, FPA2017-83946-C2-1-P, RTI2018-098868-B-I00, PPID2019-104002GB-C21, PID2019-104390GB-I00, PID2019-104714GB-C21, and PID2019-104002GB-C21 funded by MCIN/AEI/10.13039/50110001103 and “ERDF A way of making Europe” and by European Regional Development Fund, ref. no. SOMM17/6105/UGR, by Science and Technology Facilities Council (STFC) of the UK Grant No. ST/R004056/1, ST/P005314/1, ST/P003885/1, ST/V001035/1, ST/P004598/1, and ST/V001027/1, by the Bundesministerium für Bildung und Forschung under contract no. 05P21PKCI1, by the Institute of Atomic Physics project CERN-RO/ISOLDE, by the Polish Ministry of Education and Science under Contract No. 2021/WK/07 and by the Academy of Finland (Finland) Grant No. 307685.Background: The mercury isotopes around N=104 are a well-known example of nuclei exhibiting shape coexistence. Mixing of configurations can be studied by measuring the monopole strength ρ2(E0), however, currently the experimental information is scarce and lacks precision, especially for the Iπ→Iπ (I≠0) transitions. Purpose: The goals of this study were to increase the precision of the known branching ratios and internal conversion coefficients, to increase the amount of available information regarding excited states in Hg182,184,186, and to interpret the results in the framework of shape coexistence using different models. Method: The low-energy structures in Hg182,184,186 were populated in the β decay of Tl182,184,186, produced at ISOLDE, CERN and purified by laser ionization and mass separation. The γ-ray and internal conversion electron events were detected by five germanium clover detectors and a segmented silicon detector, respectively, and correlated in time to build decay schemes. Results: In total, 193, 178, and 156 transitions, including 144, 140, and 108 observed for the first time in a β-decay experiment, were assigned to Hg182,184,186, respectively. Internal conversion coefficients were determined for 23 transitions, out of which 12 had an E0 component. Extracted branching ratios allowed the sign of the interference term in Hg182 as well as ρ2(E0;02+→01+) and B(E2;02+→21+) in Hg184 to be determined. By means of electron-electron coincidences, the 03+ state was identified in Hg184. The experimental results were qualitatively reproduced by five theoretical approaches, the interacting boson model with configuration mixing with two different parametrizations, the general Bohr Hamiltonian, the beyond mean-field model, and the symmetry-conserving configuration-mixing model. However, a quantitative description is lacking. Conclusions: The presence of shape coexistence in neutron-deficient mercury isotopes was confirmed and evidence for the phenomenon existing at higher energies was found. The new experimental results provide important spectroscopic input for future Coulomb excitation studies.ISOLDE CollaborationEuropean Union’s Horizon 2020 research and innovation 654002 (ENSAR2), 665779, 771036 (CoG MAIDEN)European Regional Development Fund SOMM17/6105/UGRMCIN/AEI/10.13039/50110001103: FPA2015-64969-P, FPA2015-65035-P, FPA2017-87568-P, FPA2017-83946-C2-1-P, RTI2018-098868-B-I00, PPID2019-104002GB-C21, PID2019-104390GB-I00, PID2019-104714GB-C21, PID2019-104002GB-C2