Tuning Martensitic Phase Transition by Non-Magnetic Atom Vacancy in MnCoGe Alloys and Related Giant Magnetocaloric Effect

The effects of non-magnetic atom vacancy on structural, martensitic phase transitions and the corresponding magnetocMoric effect in MnCoGel-x alloys are investigated using x-ray diffraction and magnetic measurements. The introduction of non-magnetic atom vacancy leads to the decrease of the martensitic transition temperature and realizes a temperature window where magnetic and martensitic phase transitions can be tuned together. Moreover, the giant magnetocaloric effect accompanied with the coupled magnetic-structural transition is ob- tained. It is observed that the peak values of magnetic entropy change of MnCoGeo.97 are about -13.9, -35.1 and -47.4J.kg-1K-1 for △H = 2, 5, 7T, respectively.

A giant atom with modulated transition frequency

Giant atoms are known for the frequency-dependent spontaneous emission and associated interference effects.In this paper,we study the spontaneous emission dynamics of a two-level giant atom with dynamically modulated transition frequency.It is shown that the retarded feedback effect of the giant-atom system is greatly modified by a dynamical phase arising from the frequency modulation and the retardation effect itself.Interestingly,such a modification can in turn suppress the retarded feedback such that the giant atom behaves like a small one.By introducing an additional phase difference between the two atom-waveguide coupling paths,we also demonstrate the possibility of realizing chiral and tunable temporal profiles of the output fields.The results in this paper have potential applications in quantum information processing and quantum network engineering.

Tunable single-photon nonreciprocal scattering and targeted router in a giant atom-waveguide system with chiral couplings

We investigate the single-photon scattering properties of a driven three-level giant atom chirally coupled to two waveguides simultaneously in both the Markovian and the non-Markovian regimes.It is shown that under the Markovian limit,the chiral photon-atom interactions enable nonreciprocal scattering in a single waveguide and targeted photon routing with a probability of 100%in two waveguides,while the presence of the driving field and the giant atom structure introduce a more tunable parameter to manipulate the single-photon scattering behaviors.We also examine how the non-reciprocity and routing capability are influenced by the imperfect chirality and the atomic dissipation.In the non-Markovian regime,we show that the scattering behaviors are more complicated.The non-Markovicity induced non-reciprocity and photon routing are demonstrated in this paper.We believe that those results have potential applications in quantum network engineering.

Phase-modulated Autler–Townes splitting in a giant-atom system within waveguide QED

The nonlocal emitter-waveguide coupling,which gives birth to the so called giant atom,represents a new paradigm in the field of quantum optics and waveguide QED.We investigate the single-photon scattering in a one-dimensional waveguide on a two-level or three-level giant atom.Thanks to the natural interference induced by the back and forth photon transmitted/reflected between the atomwaveguide coupling points,the photon transmission can be dynamically controlled by the periodic phase modulation via adjusting the size of the giant atom.For the two-level giant-atom setup,we demonstrate the energy shift which is dependent on the atomic size.For the driven three-level giantatom setup,it is of great interest that,the Autler–Townes splitting is dramatically modulated by the giant atom,in which the width of the transmission valleys(reflection range)is tunable in terms of the atomic size.Our investigation will be beneficial to the photon or phonon control in quantum network based on mesoscopical or even macroscopical quantum nodes involving the giant atom.