Using RIXS and REXS, we measured the systematic modification of Cu-charge density wave in optimally doped YBa2Cu3O7, under the interfacial proximity of Nd1-x(Ca1-ySry)xMnO3 as function of the hole doping and tolerance factor of the manganite layers.

For x=0.35, we observe the Cu-CDW order with the usual dx2-y2 orbital character at Q||=0.3 r.l.u, which gets strongly enhanced as the tolerance...

Tantalum disulphide (1$T$-TaS$_2$) is a layered material which hosts an insulating commensurate charge density wave (CCDW) at temperatures below ~165K. Recent investigations of 1$T$-TaS$_2$ have revealed the existence of a metastable metallic phase accessible from this CCDW phase by applying a laser- or current pulse. Here we present Scanning Tunnelling Microscopy and Spectroscopy (STM/STS)...

The metallic kagome ferromagnet Fe$_3$Sn$_2$, which shows large spin-orbital coupling, hosts various exotic electronic/magnetic states, including flat electronic bands, massive Dirac fermions, and field-tunable nematicity. While most studies focus on the electronic degree of freedom, investigations of the spin excitations are scarce. Here we studied the character of the low-energy excitations...

RENiO3 perovskites are a handbook example of strongly correlated system, where interplay between, lattice, charge, and spin degrees of freedom leads to spontaneous metal-insulator transition. The electronic localization is associated with a charge redistribution and subtle structural distortions. Recently, intriguing phenomena like non-centrosymmetric antiferromagnetic ordering or...

Wide bandgap oxides (WBGOs) have exhibited superior material properties for power electronics and optoelectronics. However, transient electronic dynamics right after high-density carrier injection into the conduction band of WBGOs has not been fully understood. In this study, we achieved transient carrier injection in a simple cubic perovskite WBGO via ultrafast above-gap photoexcitation and...

Metal halide perovskites (MHPs) have attracted great attention in recent years due to their enormous potential for application in optoelectronic devices. However, the defects at surface/interfaces and grain boundaries of perovskite films, which impede the further enhancement of power conversion efficiency (PCE) and long-term stability of halide perovskite solar cells (PSCs), still need to be...

TiSe2 is a transition metal dichalcogenide materials that exhibits charge density wave (CDW) phase transition below T ≈ 200 K. The CDW formation is associated to a structural distortion of the lattice into a new one whose Brillouin zone size is halved.

We present a Raman spectroscopy-based approach to determine the CDW transition temperature (TCDW) of exfoliated TiSe2 onto Si/SiO2, upon...

Atomically thin transition metal dichalcogenides, such as molybdenum disulfide (MoS2), are promising candidates for opto-electronic devices because of their intrinsically strong light-matter interaction. However, excitons in monolayer MoS2 are not electrically tunable due to their limited out-of-plane extend, leading to a minimal electric dipole moment. We engineered a tunable system using...

Recent advances in signal processing enable the fundamentally faster measurement of the current-voltage characteristic for tunneling spectroscopy through the parallel demodulation of higher harmonics that are produced from nonlinearities in the tunneling junction. The local density of states (LDOS) can thus be measured in a few milliseconds. Here, we use the fast spectroscopy for quasiparticle...

The discovery of ferromagnetic 2D van der Waals (vdW) crystals allows the study of novel magnetic phenomena at a reduced dimensionality. While exfoliated 2D vdW crystals offer only limited control of their exact geometry, 2D magnets grown by molecular beam epitaxy (MBE) overcome this limitation. Here, we investigate the MBE grown 2D in-plane ferromagnet EuGe$_2$ on a nanostructured substrate...

The growth of thin films and nanostructures on solid surfaces is governed by the substrate structural properties and lattice matching. In this respect, metallic alloys can offer an interesting alternative to conventionally utilized pure metal substrates due to a larger flexibility in the effective lattice parameter. In our work we investigate the structural and electronic properties of...

Layered van der Waals chromium trihalides have received growing interest in recent years due to their extraordinary electronic and magnetic properties as well as the opportunity for the development of future functional heterostructures. We investigate the electronic configuration of CrI$_{3}$, CrBr$_{3}$, and CrCl$_{3}$ by Resonant Inelastic X-ray scattering (RIXS). The temperature-dependence...

We present a combined broadband transient reflectivity and femtosecond X-ray emission spectroscopic study of spinel Co3O4, a system representing a prototypical case of the intrinsic complexity of transition metal oxides, due to its correlated interaction of electronic, nuclear and spin degrees of freedom.

By exciting the ligand-to-metal charge transfer and metal-to-metal charge transfer...

The ultra-strong coupling between the cyclotron resonance of a 2D electron gas in a static perpendicular magnetic field and an antenna-based metamaterial that can sustain chiral electromagnetic modes gives rise to polaritonic states with opposite circular polarizations, thus providing a way to break time-reversal symmetry. To further investigate polaritons dressed by the electromagnetic vacuum...

We describe the design and characterization of using a NbFeB permanent magnet system to retrofit existing experiments with a magnetic field around 200mT. The design is compatible with UHV high-temperature sample cleaning routines which are normally above the Curie temperature of a permanent magnet.

We characterize the flux density distribution with superconducting vortices in NbSe2 and...

The two-dimensional electron gas (2DEG), formed at the surface/interface of oxide insulators, exhibits exotic physical properties. The modulation of electronic structures of 2DEG system are of crucial importance to control the properties. In this report, I will introduce the ARPES results on two 2DEG systems. (1) In amorphous LaAlO3/LaMnO3/SrTiO3, the LaMnO3 buffer layer significantly...

Recent experiments with metallic nanowire devices suggest that superconductivity can be suppressed by the application of electric fields, at odds with current understanding of electrostatic screening in metals. We demonstrate that the control of superconductivity in such switches does not depend on the presence of an electric field at the nanowire surface but requires a current of high-energy...

The kagome lattice, the most prominent structural motif in quantum physics, benefits from inherent nontrivial geometry to host diverse quantum phases. We utilized muon-spin relaxation to probe charge order and superconductivity in kagome superconductors (K,Rb)V$_{3}$Sb$_{5}$ [1]. We observe a striking enhancement of the internal field width sensed by the muon ensemble, which takes place just...

High-temperature superconducting cuprates are an excellent model system to study the relationship between intertwined quantum phases. We aimed to influence the competition between superconductivity and charge order in La2-xSrxCuO4 (LSCO) by applying strain along the tetragonal *c*-axis direction, tuning the next-nearest neighbour hopping strength. X-ray diffraction measurements were performed...

We compare the infrared responses of the underdoped cuprate superconductor YBa2Cu3O6.6 and the so-called telephone-number-compound Sr2Ca12Cu24O41. The charge carriers of the latter reside in layers of weakly coupled two-leg ladders.

The response of YBa2Cu3O6.6 was previously shown to exhibit a characteristic pseudogap and precursor superconducting pairing that develop well above Tc [1]. The...

Superconductivity with a critical temperature $T_C$ $\sim$ 5.25 K was recently reported in the Cr-based superconductor Pr$_3$Cr$_{10-x}$N$_{11}$. The large upper critical field $H_{C2}$ $\sim$ 20 T, and the strong correlation between 3$d$ electrons derived from specific heat, suggest the unconventional superconductivity nature of this compound. We performed muon-spin rotation/relaxation...

Experimentally simple cubic phosphorus displays a peculiar pressure-$T_c$ curve with valley- and ridge-like features between 12 and 50 GPa. From the theoretical side, a simple electron-phonon mechanism proves insufficient to describe this behaviour. To address possible effects coming from electronic correlations and plasmonic contributions we have solved the parameter free gap equation of...

Kagome materials have attracted much interest recently as they may host topological bands, flat bands, superconductivity, unconventional magnetic properties, etc. In this talk, we present our work on one example of magnetic Weyl kagome material called Fe3Sn2 by using laser micro-ARPES. With a small spatial resolution of a few microns of the laser, we show that the breathing kagome pattern in...

The generalization of the notion of nonunitary superconductivity to complex materials with multiple internal degrees of freedom (such as orbitals, sublattices, or layers) opens multiple possibilities. Focusing on d-electron systems with two orbitals, we can address a variety of complex quantum materials and discuss the consequences for the superconducting spectra. In particular, gap openings...

Transport of electromagnetic waves in 2D disordered hyperuniform structures shows an interesting behavior. Indeed, at least 5 different transport regimes have been recognized, like Anderson localization or diffusion. A traditionally used method to determine the transport regime associated with a wave function is the inverse participation ratio.

Unfortunately, this method leads to...

We present a new diagrammatic Monte Carlo impurity solver based on the strong-coupling expansion of the vertex functions. By directly sampling the four-point pseudo-particle vertex diagrams and applying the self-consistency equation at the level of the triangular vertex, we significantly improve the traditional schemes such as non-crossing approximation, and achieve numerically exact results....

Identifying relevant coarse degrees of freedom in a complex system is a key stage in developing effective theories. The renormalisation group provides a framework for this, but its practical execution in unfamiliar systems is fraught with ad-hoc choices, whereas machine learning approaches, though promising, often lack formal interpretability. Recently, the optimal coarse-graining rule was...

Laws of friction have been studied since 500 years, yet their microscopic underpinning still eludes us. We do not understand how slip events are nucleated, nor what controls the distribution of their magnitude; questions that are central in earthquake science. We provide a novel framework to capture these phenomena by considering how continuum descriptions (rate-and-state laws) are perturbed...

Preparation of quantum states in form of a variational quantum circuit plays a crucial role in quantum computing. We show that, in addition to circuit architecture, the fidelity of the prepared state depends non-trivially on the number of circuit shots $N_s$ used in gradient descent. Namely, we observe that fidelity shows a critical behavior in $N_s$, giving rise to the notion of critical...

A subroutine of many quantum algorithms is the diagonalization of Pauli operators. Although it is always possible to construct a quantum circuit that simultaneously diagonalizes commuting Pauli operators, only resource-efficient circuits are reliably executable on near-term quantum computers. Generic circuits lead to a Swap-gate overhead on quantum devices with limited connectivity. A common...

A few years ago [1], it was proposed that materials hosting narrow topological bands can support nontrivial superfluid weight, with Tc beyond the conventional BCS limits. This behavior roots to the large spread of electronic orbitals in topological bands, which is linked to properties of quantum metrics associated with electronic Bloch states [2,3]. We present a new perspective for quantum...

We observe how vacuum cavity fields modify magneto-transport in the integer quantum Hall effect. In particular, odd filling factors lose their quantization, while fractional states remain intact. We quantitatively describe this loss of quantization as vacuum field induced resistivity. In our interpretation the interaction with vacuum fields adds a long range perturbation to the system, making...

Endofullerenes are candidate systems for molecular spintronics and electronics. Ho3N@C80 has been studied using x-ray absorption spectroscopy (XAS) at different temperatures with a low noise Everthart-Thornley detector at the PEARL beamline of the Swiss Light Source. Molecules were air-brushed on a graphene substrate, then introduced into vacuum and annealed. X-ray photoelectron spectroscopy...

K3+xC60 film exhibits Mott transitions and superconductivity, depending on dimensionality and doping. Surprisingly, in the trilayer case, a strong electron-hole doping asymmetry has been observed in the SC-phase absent in the bulk. Using DFT+DMFT, we show this doping asymmetry results from a substantial charge reshuffling from the top layer to the middle layer. While the nominal filling per...

Among first row transition metal oxides, the perovskite oxide SrCrO3 (SCO) remain only vaguely explored. Its properties are still controversial and under debate. Interestingly, this compound has been observed to be metallic and antiferromagnetic at the same time. The goal of this study is to uncover the electric behaviour of SCO thin films as function of strain. Temperature-dependent transport...

I will present muon spin rotation and magnetic susceptibility experiments on in-plane stress effects on the static spin-stripe order and superconductivity in the cuprate system La$_{2-x}$Ba$_{x}$CuO$_{4}$ with $x=0.115$ [1]. An extremely low uniaxial stress of ${\sim}$0.1 GPa induces a substantial decrease in the magnetic volume fraction and a dramatic rise in the onset of 3D...

We use finite-temperature tensor network algorithms to investigate the spin-1/2 J1−J2 Heisenberg model on the square lattice. We provide strong numerical evidence in favor of an Ising transition in the collinear phase of the model, confirming a 30 years old field theory prediction. In units of J2, the critical temperature reaches a maximal value of Tc/J2≃0.18 around J2/J1≃1.0. It is strongly...

Dynamical quantum phase transitions (DQPTs) upon quantum quenches are useful for the identification of non-trivial topology of non-interacting systems [1]. Periodic occurrences of DQPTs are guaranteed in Chern insulators if the moduli of initial and final Hamiltonians are different. Whether such a sufficient condition holds for interacting systems has remained elusive. To this end, we study...