Energy-dependent spatial texturing of the charge order in 1T1T-Cux_xTiSe2_2

We report a detailed study of the microscopic effects of Cu intercalation on the charge density wave (CDW) in 1\textit{T}-Cu$_x$TiSe$_2$. Scanning tunneling microscopy and spectroscopy (STM/STS) reveal a unique, Cu driven spatial texturing of the charge ordered phase, with the appearance of energy dependent CDW patches and sharp $\pi$-phase shift domain walls ($\pi$DWs). The energy and doping dependencies of the patchwork are directly linked to the inhomogeneous potential landscape due to the Cu intercalants. They imply a CDW gap with unusual features, including a large amplitude, the opening below the Fermi level and a shift to higher binding energy with electron doping. Unlike the patchwork, the $\pi$DWs occur independently of the intercalated Cu distribution. They remain atomically sharp throughout the investigated phase diagram and occur both in superconducting and non-superconducting specimen. These results provide unique atomic-scale insight on the CDW ground state, questioning the existence of incommensurate CDW domain walls and contributing to understand its formation mechanism and interplay with superconductivity

Dimensional cross-over of the charge density wave order parameter in thin exfoliated 1T-VSe2_2

The capability to isolate one to few unit-cell thin layers from the bulk matrix of layered compounds opens fascinating prospects to engineer novel electronic phases. However, a comprehensive study of the thickness dependence and of potential extrinsic effects are paramount to harness the electronic properties of such atomic foils. One striking example is the charge density wave (CDW) transition temperature in layered dichalcogenides whose thickness dependence remains unclear in the ultrathin limit. Here we present a detailed study of the thickness and temperature dependences of the CDW in VSe$_2$ by scanning tunnelling microscopy (STM). We show that mapping the real-space CDW periodicity over a broad thickness range unique to STM provides essential insight. We introduce a robust derivation of the local order parameter and transition temperature based on the real space charge modulation amplitude. Both quantities exhibit a striking non-monotonic thickness dependence that we explain in terms of a 3D to 2D dimensional crossover in the FS topology. This finding highlights thickness as a true tuning parameter of the electronic ground state and reconciles seemingly contradicting thickness dependencies determined in independent transport studies

Holographic imaging of the complex charge density wave order parameter

The charge density wave (CDW) in solids is a collective ground state combining lattice distortions and charge ordering. It is defined by a complex order parameter with an amplitude and a phase. The amplitude and wavelength of the charge modulation are readily accessible to experiment. However, accurate measurements of the corresponding phase are significantly more challenging. Here we combine reciprocal and real space information to map the full complex order parameter based on topographic scanning tunneling microscopy (STM) images. Our technique overcomes limitations of earlier Fourier space based techniques to achieve distinct amplitude and phase images with high spatial resolution. Applying this analysis to transition metal dichalcogenides provides striking evidence that their CDWs consist of three individual charge modulations whose ordering vectors are connected by the fundamental rotational symmetry of the crystalline lattice. Spatial variations in the relative phases of these three modulations account for the different contrasts often observed in STM topographic images. Phase images further reveal topological defects and discommensurations, a singularity predicted by theory for a nearly commensurate CDW. Such precise real space mapping of the complex order parameter provides a powerful tool for a deeper understanding of the CDW ground state whose formation mechanisms remain largely unclear

Delusive chirality and periodic strain pattern in moir\'{e} systems

Geometric phase analysis (GPA) is a widely used technique for extracting displacement and strain fields from scanning probe images. Here, we demonstrate that GPA should be implemented with caution when several fundamental lattices contribute to the image, in particular in twisted heterostructures featuring moir\'e patterns. We find that in this case, GPA is likely to suggest the presence of chiral displacement and periodic strain fields, even if the structure is completely relaxed and without distortions. These delusive fields are subject to change with varying twist angles, which could mislead the interpretation of twist angle dependent properties

Income Diversification of Farm Households: Relevance and Determinants in Germany

During recent years, the number of farms able to generate satisfactory income from agricultural production has continuously decreased in advanced economies. The main reasons are the implementation of the Common Agricultural Policy of 1992 and the increasing capitalization of the primary sector. The relevance of income diversification and interest in various development paths of rural households have, therefore, been renewed in political-economic debates in those countries. The aim of this study is to identify factors that determine income diversification in Germany. An econometric model has been estimated based on a comprehensive survey’s data. The results show that the main economic incentive for farm diversification is the expected income increase or resource allocation, whereas risk minimization is less relevant. Access to resources (labor, capital) is an important requirement for tapping alternative economic activities. Other significant variables include the education of the farmer as well as his experience in managing the farm. These findings are relevant for designing effective agricultural policy measures to explicitly meet the heterogeneous needs of the rural households.Income diversification, farm household, survey, Germany, Consumer/Household Economics,

Twist angle dependent electronic properties of exfoliated single layer MoS2_2 on Au(111)

Synthetic materials and heterostructures obtained by the controlled stacking of exfoliated monolayers are emerging as attractive functional materials owing to their highly tunable properties. We present a detailed scanning tunneling microscopy and spectroscopy study of single layer MoS$_2$-on-gold heterostructures as a function of twist angle. We find that their electronic properties are determined by the hybridization of the constituent layers and are modulated at the moir\'e period. The hybridization depends on the layer alignment and the modulation amplitude vanishes with increasing twist angle. We explain our observations in terms of a hybridization between the nearest sulfur and gold atoms, which becomes spatially more homogeneous and weaker as the moir\'e periodicity decreases with increasing twist angle, unveiling the possibility of tunable hybridization of electronic states via twist angle engineering

Simultaneous Integrated Boost Intensity‑Modulated Radiotherapy (SIB‑IMRT) in Nasopharyngeal Cancer

Abstract : Purpose: : To assess the efficacy and safety of using simultaneous integrated boost intensity-modulated radiotherapy (SIB-IMRT) to treat nasopharyngeal cancer (NPC) in a Caucasian cohort. Outcome was analyzed with respect to dose-volume histogram (DVH) values. Patients and Methods: : Between 03/2002 and 01/2008, 39 NPC patients underwent SIB-IMRT (37 Caucasians; 31 males; mean age 53 years [16-78 years]). 41% presented with WHO (World Health Organization) type 1 unfavorable histology, 85% with stage III/IV disease. 19 patients had total gross tumor volume (GTV) 16-70 cm3 (mean 36 cm3), while 16 had GTV > 70 cm3 (73-217 cm3; mean 115 cm3). All patients with stage II-IV disease received concomitant cisplatin. The prescribed SIB dose delivered to the planning target volume (PTV) was 70 Gy (2.00 Gy/fraction) in 17, 69.6 Gy (2.11 Gy/fraction) in 19, and 66 Gy (2.20 Gy/fraction) in three patients. Results: : 3-year local relapse-free, nodal relapse-free, distant metastases-free, disease-free rates and overall survival were 86%, 89%, 85%, 72%, and 85% (median follow-up 30 months [8-71 months]). Histology was a significant prognostic factor concerning overall survival, with worst prognosis in WHO type 1 compared to type 2/3 (75% vs. 93%; p = 0.03). There was a trend in favor of WHO type 2/3 regarding local control (74% vs. 94%; p = 0.052). The PTV DVHs showed a slight left shift compared to reported series. Three patients developed grade 3 late effects (xerostomia [n = 2], dysphagia [n = 1], hearing loss [n = 1]). Conclusion: : In comparison with predominantly Asian NPC IMRT series in the literature, chemo-IMRT in the own Caucasian cohort, characterized by less radioresponsive WHO type 1, was equally effective. Treatment tolerance was excellen

Revisiting the vortex-core tunnelling spectroscopy in YBa2_2Cu3_3O7−δ_{7-\delta}

The observation by scanning tunnelling spectroscopy (STS) of Abrikosov vortex cores in the high-temperature superconductor YBa$_2$Cu$_3$O$_{7-\delta}$ (Y123) has revealed a robust pair of electron-hole symmetric states at finite subgap energy. Their interpretation remains an open question because theory predicts a different signature in the vortex cores, characterised by a strong zero-bias conductance peak. We present STS data on very homogeneous Y123 at 0.4 K revealing that the subgap features do not belong to vortices: they are actually observed everywhere along the surface with high spatial and energy reproducibility, even in the absence of magnetic field. Detailed analysis and modelling show that these states remain unpaired in the superconducting phase and belong to an incoherent channel which contributes to the tunnelling signal in parallel with the superconducting density of states.Comment: Final version with supplementary materia