High-quality Sr₂CrWO₆ (SCWO) films have been grown on SrTiO₃ (STO) substrate by pulsed laser deposition under low oxygen pressure. With decrease of the film thickness, a drastic conductivity increase is observed. The Hall measurements show that the thicker the film, the lower the carrier density. An extrinsic mechanism of charge doping due to the dominance of oxygen vacancies at SCWO/STO interfaces is proposed. The distribution and gradient of carrier concentration in SCWO films are considered to be related to this phenomenon. Resistivity behavior observed in these films is found to follow the variable range hopping model. It is revealed that with increase of the film thickness, the extent of disorder in the lattice increases, which gives a clear evidence of disorder-induced localization charge carriers in these films. Magnetoresistance measurements show that there is a negative magnetoresistance in SCWO films, which is considered to be caused by the magnetic scattering of magnetic elements Cr³⁺ and W⁵⁺. In addition, a sign reversal of anisotropic magnetoresistance (AMR) in SCWO film is observed for the first time, when the temperature varies across a characteristic value, T_M. Magnetization—temperature measurements demonstrate that this AMR sign reversal is caused by the direction transition of easy axis of magnetization from the in-plane ferromagnetic order at T > T_M to the out-of-plane at T < T_M.

As a special order of electronic correlation induced by spatial modulation, the charge density wave (CDW) phenomena in condensed matters attract enormous research interests. Here, using scanning—tunneling microscopy in various temperatures, we discover a hidden incommensurate stripe-like CDW order besides the ($sqrt{7}$ × $sqrt{3}$) CDW phase at low-temperature of 4 K in the epitaxial monolayer 1T-VSe₂} film. Combining the variable-temperature angle-resolved photoemission spectroscopic (ARPES) measurements, we discover a two-step transition of an anisotropic CDW gap structure that consists of two parts Δ₁ and Δ₂. The gap part Δ₁ that closes around ～ 150 K is accompanied with the vanish of the ($sqrt{7}$ × $sqrt{3}$) CDW phase. While another momentum-dependent gap part Δ₂ can survive up to ～ 340 K, and is suggested to the result of the incommensurate CDW phase. This two-step transition with anisotropic gap opening and the resulted evolution in ARPES spectra are corroborated by our theoretical calculation based on a phenomenological form for the self-energy containing a two-gap structure Δ₁ + Δ₂, which suggests different forming mechanisms between the ($sqrt{7}$ × $sqrt{3}$) and the incommensurate CDW phases. Our findings provide significant information and deep understandings on the CDW phases in monolayer 1T-VSe₂} film as a two-dimensional (2D) material.

Frequency up-conversion is an effective method of mid-infrared (MIR) detection by converting long-wavelength photons to the visible domain, where efficient detectors are readily available. Here, we generate MIR light carrying orbital angular momentum (OAM) from a difference frequency generation process and perform up-conversion on it via sum frequency conversion in a bulk quasi-phase-matching crystal. The maximum quantum conversion efficiencies from MIR to visible are 34.0%, 10.4%, and 3.5% for light with topological charges of 0, 1, and 2, respectively, achieved by utilizing an optimized strong pump light. We also verify the OAM conservation with a specially designed interferometer, and the results agree well with the numerical simulations. Our study opens up the possibilities for generating, manipulating, and detecting MIR light that carries OAM, and will have great potential for optical communications and remote sensing in the MIR regime.

In contrast to interferometry-based quantum sensing, where interparticle interaction is detrimental, quantum many-body probes exploit such interactions to achieve quantum-enhanced sensitivity. In most of the studied quantum many-body probes, the interaction is considered to be short-ranged. Here, we investigate the impact of long-range interaction at various filling factors on the performance of Stark quantum probes for measuring a small gradient field. These probes harness the ground state Stark localization phase transition which happens at an infinitesimal gradient field as the system size increases. Our results show that while super-Heisenberg precision is always achievable in all ranges of interaction, the long-range interacting Stark probe reveals two distinct behaviors. First, by algebraically increasing the range of interaction, the localization power is enhanced and thus the sensitivity of the probe decreases. Second, as the interaction range becomes close to a fully connected graph its effective localization power disappears and thus the sensitivity of the probe starts to enhance again. The super-Heisenberg precision is achievable throughout the extended phase until the transition point and remains valid even when the state preparation time is incorporated in the resource analysis. As the probe enters the localized phase, the sensitivity decreases and its performance becomes size-independent, following a universal behavior. In addition, our analysis shows that lower filling factors lead to better precision for measuring weak gradient fields.

Wavefunction is a fundamental concept of quantum theory. Recent studies have shown surprisingly that wavefunction can be directly reconstructed via the measurement of weak value. The weak value based direct wavefunction reconstruction not only gives the operational meaning of wavefunction, but also provides the possibility of realizing holographic imaging with a totally new quantum approach. Here, we review the basic background knowledge of weak value based direct wavefunction reconstruction combined with recent experimental demonstrations. The main purpose of this work focuses on the idea of holographic imaging via direct wavefunction reconstruction. Since research on this topic is still in its early stage, we hope that this work can attract interest in the field of traditional holographic imaging. In addition, the wavefunction holographic imaging may find important applications in quantum information science.