Giordano MATTONI

@article{uchida2022high,

title = {High-order harmonic generation and its unconventional scaling law in the Mott-insulating Ca_{2}RuO_{4}},

author = {K Uchida and G Mattoni and S Yonezawa and F Nakamura and Y Maeno and K Tanaka},

url = {https://arxiv.org/abs/2106.15478},

doi = {10.1103/PhysRevLett.128.127401},

year  = {2022},

date = {2022-03-23},

urldate = {2022-03-23},

journal = {Physical Review Letters},

volume = {128},

number = {127401},

abstract = {Competition and cooperation among orders is at the heart of many-body physics in strongly correlated materials and leads to their rich physical properties. It is crucial to investigate what impact many-body physics has on extreme nonlinear optical phenomena, with the possibility of controlling material properties by light. However, the effect of competing orders and electron-electron correlations on highly nonlinear optical phenomena has not yet been experimentally clarified. Here, we investigated high-order harmonic generation from the Mott-insulating phase of Ca2RuO4. Changing the gap energy in Ca2RuO4 as a function of temperature, we observed a strong enhancement of high order harmonic generation at 50 K, increasing up to several hundred times compared to room temperature. We discovered that this enhancement can be well reproduced by an empirical scaling law that depends only on the material gap energy and photon emission energy. Such a scaling law can hardly be explained by the electronic structure change in the single particle model and has not been predicted by previous theoretical studies on HHG in the simple Mott-Hubbard model. Our results suggest that the highly nonlinear optical response of strongly correlated materials is influenced by competition among the multiple degrees of freedom and electron-electron correlations.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{mattoni2020role,

title = {Role of local temperature in the current-driven metal–insulator transition of Ca_{2}RuO_{4}},

author = {G Mattoni and S Yonezawa and F Nakamura and Y Maeno},

url = {https://arxiv.org/abs/2007.06885},

doi = {10.1103/PhysRevMaterials.4.114414},

year  = {2020},

date = {2020-11-17},

journal = {Physical Review Materials},

volume = {4},

number = {114414},

abstract = {It was recently reported that a continuous electric current is a powerful control parameter to trigger changes in the electronic structure and metal–insulator transitions (MITs) in Ca2RuO4. However, the spatial evolution of the MIT and the implications of the unavoidable Joule heating have not been clarified yet, often hindered by the difficulty to assess the local sample temperature. In this work, we perform infrared thermal imaging on single-crystal Ca2RuO4 while controlling the MIT by electric current. The change in emissivity at the phase transition allows us to monitor the gradual formation and expansion of the metallic phase upon increasing current. Our local temperature measurements indicate that, within our experimental resolution, the MIT always occurs at the same local transition temperatures, irrespective of whether it is driven by temperature or current. Our results highlight the importance of local heating, phase coexistence, and microscale inhomogeneity when studying strongly correlated materials under the flow of electric current.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{mattoni2020diamagnetic,

title = {Diamagnetic-like response from localized heating of a paramagnetic material},

author = {G Mattoni and S Yonezawa and Y Maeno},

url = {https://arxiv.org/abs/2004.04570},

doi = {10.1063/5.0006098},

year  = {2020},

date = {2020-04-30},

journal = {Applied Physics Letters},

volume = {116},

number = {17},

pages = {172405},

publisher = {AIP Publishing LLC},

abstract = {In the search of material properties out-of-equilibrium, the non-equilibrium steady states induced by electric current are an appealing research direction where unconventional states may emerge. However, the unavoidable Joule heating caused by flowing current calls for the development of new measurement protocols, with a particular attention to the physical properties of the background materials involved. Here, we demonstrate that localised heating can give rise to a large, spurious diamagnetic-like signal. This occurs due to the local reduction of the background magnetisation caused by the heated sample, provided that the background material has a Curie-like susceptibility. Our experimental results, along with numerical calculations, constitute an important building block for performing accurate magnetic measurements under the flow of electric current.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Sow2019,

title = {In situ control of diamagnetism by electric current in Ca_{3}(Ru_{1-x}Ti_{x})_{2}O_{7}},

author = {C Sow and R Numasaki and G Mattoni and S Yonezawa and N Kikugawa and S Uji and Y Maeno},

url = {https://arxiv.org/abs/1902.02515},

doi = {10.1103/PhysRevLett.122.196602},

year  = {2019},

date = {2019-05-17},

journal = {Physical Review Letters},

volume = {122},

number = {19},

abstract = {Nonequilibrium steady state conditions induced by a dc current can alter the physical properties of strongly correlated electron systems. In this regard, it was recently shown that dc current can trigger novel electronic states, such as current-induced diamagnetism, which cannot be realized in equilibrium conditions. However, reversible control of diamagnetism has not been achieved yet. Here, we demonstrate reversible in situ control between a Mott insulating state and a diamagnetic semimetal-like state by a dc current in the Ti-substituted bilayer ruthenate Ca3(Ru1-xTix)2O7 (x=0.5%). By performing simultaneous magnetic and resistive measurements, we map out the temperature vs current-density phase diagram in the nonequilibrium steady state of this material. The present results open up the possibility of creating novel electronic states in a variety of strongly correlated electron systems under dc current. © 2019 American Physical Society.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}