Intertwined quantum phase transitions in the even-even 90-100Sr isotopes
Abstract
The even-even 90-100Sr isotopes are identified as a region of intertwined quantum phase transitions (IQPTs). In this scenario, a quantum phase transition involving the crossing of normal and intruder configurations is accompanied by a shape evolution within the intruder configuration. Using the interacting boson model with configuration mixing (IBM-CM), we show that the strontium chain exhibits coexisting Type I and Type II QPTs, where the intruder configuration evolves from a near-spherical structure in 90-96Sr to a deformed one in 98,100Sr, while the normal and intruder configurations cross between 96Sr and 98Sr. As a result, the ground state changes abruptly from a weakly collective normal configuration to a deformed intruder configuration. Evidence for this scenario is provided by a detailed comparison with experimental excitation energies, spectroscopic quadrupole moments, isotope shifts, and monopole E0 transition strengths, together with the configuration and nd decompositions of the calculated wave functions. The results place the strontium isotopes alongside the neighboring zirconium chain as another realization of IQPTs in the intricate A≈100 region.
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