arXiv subjects

Natasha Kiper

Publications and source records attributed to Natasha Kiper.

3 recordsLinked to original sources

arXiv2026

Photon Correlation Spectroscopy as a Probe of Critical Fluctuations in Correlated Electron Systems

Characterizing phase transitions between correlated electronic phases, extracting their critical exponents, and identifying their universality class are of central interest in many-body physics. Here, we propose and demonstrate that photon correlation spectroscopy can be used to gain insight into the nature of critical electronic density fluctuations. We study a semiconductor moir\'e material consisting of two MoSe2 layers separated by a monolayer h-BN spacer and measure interlayer electron dynamics via the second-order correlation function of the scattered photons. The correlated transfer of large numbers of electrons between the layers at the onset of an Ising-type layer pseudo-spin phase transition leads to photon bunching in light scattered by the exciton resonance of one layer. Our measurements pave the way for using photon correlations as a method to access dynamical exponents associated with electronic phase transitions.

cond-mat.str-el↗

arXiv2024

Confined Trions and Mott-Wigner States in a Purely Electrostatic Moiré Potential

Moiré heterostructures consisting of transition metal dichalcogenide (TMD) hetero- and homobilayers have emerged as a promising material platform to study correlated electronic states. Optical signatures of strong correlations in the form of Mott-Wigner states and fractional Chern insulators have already been observed in TMD monolayers and their twisted bilayers. In this work, we use a moiré substrate containing a twisted hexagonal boron nitride (h-BN) interface to externally generate a superlattice potential for the TMD layer: the periodic structure of ferroelectric domains in h-BN effects a purely electrostatic potential for charge carriers. We find direct evidence for the induced moiré potential in the emergence of new excitonic resonances at integer fillings, and our observation of an enhancement of the trion binding energy by $\simeq$ 3 meV. A theoretical model for exciton-electron interactions allows us to directly determine the moiré potential modulation of 30$\pm$5 meV from the measured trion binding energy shift. We obtain direct evidence for charge order linked to electronic Mott-Wigner states at filling factors $ν$ = 1/3 and $ν$ = 2/3 through the associated exciton Umklapp resonances.

cond-mat.str-el↗

arXiv2023

Kinetic Magnetism in Triangular Moiré Materials

Magnetic properties of materials ranging from conventional ferromagnetic metals to strongly correlated materials such as cuprates originate from Coulomb exchange interactions. The existence of alternate mechanisms for magnetism that could naturally facilitate electrical control have been discussed theoretically but an experimental demonstration in an extended system has been missing. Here, we investigate MoSe$_2$/WS$_2$ van der Waals heterostructures in the vicinity of Mott insulator states of electrons forming a frustrated triangular lattice and observe direct evidence for magnetic correlations originating from a kinetic mechanism. By directly measuring electronic magnetization through the strength of the polarization-selective attractive polaron resonance, we find that when the Mott state is electron doped the system exhibits ferromagnetic correlations in agreement with the Nagaoka mechanism.

cond-mat.str-el↗