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<jats:p>Understanding the interplay between superconductivity and charge-density wave (CDW) in NbSe<jats:sub>2</jats:sub> is vital for both fundamental physics and future device applications. Here, combining scanning tunneling microscopy, angle-resolved photoemission spectroscopy and Raman spectroscopy, we study the CDW phase in the monolayer NbSe<jats:sub>2</jats:sub> films grown on various substrates of bilayer graphene (BLG), SrTiO<jats:sub>3</jats:sub>(111), and Al<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub>(0001). It is found that the two stable CDW states of monolayer NbSe<jats:sub>2</jats:sub> can coexist on NbSe<jats:sub>2</jats:sub>/BLG surface at liquid-nitrogen temperature. For the NbSe<jats:sub>2</jats:sub>/SrTiO<jats:sub>3</jats:sub>(111) sample, the unidirectional CDW regions own the kinks at ±41 meV and a wider gap at 4.2 K. It is revealed that the charge transfer from the substrates to the grown films will influence the configurations of the Fermi surface, and induce a 130 meV lift-up of the Fermi level with a shrink of the Fermi pockets in NbSe<jats:sub>2</jats:sub>/SrTiO<jats:sub>3</jats:sub>(111) compared with the NbSe<jats:sub>2</jats:sub>/BLG. Combining the temperature-dependent Raman experiments, we suggest that the electron-phonon coupling in monolayer NbSe<jats:sub>2</jats:sub> dominates its CDW phase transition.</jats:p>

<jats:p>We systemically investigate the nature of Ce 4<jats:italic>f</jats:italic> electrons in structurally layered heavy-fermion compounds Ce<jats:sub> <jats:italic>m</jats:italic> </jats:sub> <jats:italic>M</jats:italic> <jats:sub> <jats:italic>n</jats:italic> </jats:sub>In<jats:sub>3<jats:italic>m</jats:italic> + 2<jats:italic>n</jats:italic> </jats:sub> (with <jats:italic>M</jats:italic> = Co, Rh, Ir, and Pt, <jats:italic>m</jats:italic> = 1, 2, <jats:italic>n</jats:italic> = 0–2), at low temperature using on-resonance angle-resolved photoemission spectroscopy. Three heavy quasiparticle bands <jats:italic>f</jats:italic> <jats:sup>0</jats:sup>, <jats:inline-formula> <jats:tex-math><?CDATA ${f}_{7/2}^{1}$?></jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msubsup> <mml:mi>f</mml:mi> <mml:mrow> <mml:mn>7</mml:mn> <mml:mo stretchy="false">/</mml:mo> <mml:mn>2</mml:mn> </mml:mrow> <mml:mn>1</mml:mn> </mml:msubsup> </mml:mrow> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpl_38_10_107402_ieqn1.gif" xlink:type="simple" /> </jats:inline-formula> and <jats:inline-formula> <jats:tex-math><?CDATA ${f}_{5/2}^{1}$?></jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msubsup> <mml:mi>f</mml:mi> <mml:mrow> <mml:mn>5</mml:mn> <mml:mo stretchy="false">/</mml:mo> <mml:mn>2</mml:mn> </mml:mrow> <mml:mn>1</mml:mn> </mml:msubsup> </mml:mrow> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpl_38_10_107402_ieqn2.gif" xlink:type="simple" /> </jats:inline-formula>, are observed in all compounds, whereas their intensities and energy locations vary greatly with materials. The strong <jats:italic>f</jats:italic> <jats:sup>0</jats:sup> states imply that the localized electron behavior dominates the Ce 4<jats:italic>f</jats:italic> states. The Ce 4<jats:italic>f</jats:italic> electrons are partially hybridized with the conduction electrons, making them have the dual nature of localization and itinerancy. Our quantitative comparison reveals that the <jats:inline-formula> <jats:tex-math><?CDATA ${f}_{5/2}^{1}$?></jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msubsup> <mml:mi>f</mml:mi> <mml:mrow> <mml:mn>5</mml:mn> <mml:mo stretchy="false">/</mml:mo> <mml:mn>2</mml:mn> </mml:mrow> <mml:mn>1</mml:mn> </mml:msubsup> </mml:mrow> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpl_38_10_107402_ieqn3.gif" xlink:type="simple" /> </jats:inline-formula>–<jats:italic>f</jats:italic> <jats:sup>0</jats:sup> intensity ratio is more suitable to reflect the 4<jats:italic>f</jats:italic>-state hybridization strength.</jats:p>

<jats:p>Signatures of topological superconductivity (TSC) in superconducting materials with topological nontrivial states prompt intensive researches recently. Utilizing high-resolution angle-resolved photoemission spectroscopy and first-principles calculations, we demonstrate multiple Dirac fermions and surface states in superconductor BaSn<jats:sub>3</jats:sub> with a critical transition temperature of about 4.4 K. We predict and then unveil the existence of two pairs of type-I topological Dirac fermions residing on the rotational axis. Type-II Dirac fermions protected by screw axis are confirmed in the same compound. Further calculation for the spin helical texture of the observed surface states originating from the Dirac fermions gives an opportunity for realization of TSC in one single material. Hosting multiple Dirac fermions and topological surface states, the intrinsic superconductor BaSn<jats:sub>3</jats:sub> is expected to be a new platform for further investigation of topological quantum materials as well as TSC.</jats:p>

<jats:p>Recently, intrinsic antiferromagnetic topological insulator MnBi<jats:sub>2</jats:sub>Te<jats:sub>4</jats:sub> has drawn intense research interest and leads to plenty of significant progress in physics and materials science by hosting quantum anomalous Hall effect, axion insulator state, and other quantum phases. An essential ingredient to realize these quantum states is the magnetic gap in the topological surface states induced by the out-of-plane ferromagnetism on the surface of MnBi<jats:sub>2</jats:sub>Te<jats:sub>4</jats:sub>. However, the experimental observations of the surface gap remain controversial. Here, we report the observation of the surface gap via the point contact tunneling spectroscopy. In agreement with theoretical calculations, the gap size is around 50 meV, which vanishes as the sample becomes paramagnetic with increasing temperature. The magnetoresistance hysteresis is detected through the point contact junction on the sample surface with an out-of-plane magnetic field, substantiating the surface ferromagnetism. Furthermore, the non-zero transport spin polarization coming from the ferromagnetism is determined by the point contact Andreev reflection spectroscopy. Combining these results, the magnetism-induced gap in topological surface states of MnBi<jats:sub>2</jats:sub>Te<jats:sub>4</jats:sub> is revealed.</jats:p>

<jats:p>In the last decade, perovskite solar cells (PSCs) have greatly drawn researchers’ attention, with the power conversion efficiency surging from 3.8% to 25.5%. PSCs possess the merits of low cost, simple fabrication process and high performance, which could be one of the most promising photovoltaic technologies in the future. In this review, we focus on the summary of the updated progresses in single junction PSCs including efficiency, stability and large area module. Then, the important progresses in tandem solar cells are briefly discussed. A prospect into the future of the field is also included.</jats:p>

<jats:p>We should add the following acknowledge: Jing Teng thanks the support from the Youth Innovation Promotion Association Project, Chinese Academy of Sciences.</jats:p>

<jats:p>Human experts cannot efficiently access physical information of a quantum many-body states by simply “reading” its coefficients, but have to reply on the previous knowledge such as order parameters and quantum measurements. We demonstrate that convolutional neural network (CNN) can learn from coefficients of many-body states or reduced density matrices to estimate the physical parameters of the interacting Hamiltonians, such as coupling strengths and magnetic fields, provided the states as the ground states. We propose QubismNet that consists of two main parts: the Qubism map that visualizes the ground states (or the purified reduced density matrices) as images, and a CNN that maps the images to the target physical parameters. By assuming certain constraints on the training set for the sake of balance, QubismNet exhibits impressive powers of learning and generalization on several quantum spin models. While the training samples are restricted to the states from certain ranges of the parameters, QubismNet can accurately estimate the parameters of the states beyond such training regions. For instance, our results show that QubismNet can estimate the magnetic fields near the critical point by learning from the states away from the critical vicinity. Our work provides a data-driven way to infer the Hamiltonians that give the designed ground states, and therefore would benefit the existing and future generations of quantum technologies such as Hamiltonian-based quantum simulations and state tomography.</jats:p>

<jats:p>Helical edge states are the hallmark of the quantum spin Hall insulator. Recently, several experiments have observed transport signatures contributed by trivial edge states, making it difficult to distinguish between the topologically trivial and nontrivial phases. Here, we show that helical edge states can be identified by the random-gate-voltage induced <jats:italic>Φ</jats:italic> <jats:sub>0</jats:sub>/2-period oscillation of the averaged electron return probability in the interferometer constructed by the edge states. The random gate voltage can highlight the <jats:italic>Φ</jats:italic> <jats:sub>0</jats:sub>/2-period Al’tshuler–Aronov–Spivak oscillation proportional to sin<jats:sup>2</jats:sup>(2<jats:italic>πΦ</jats:italic>/<jats:italic>Φ</jats:italic> <jats:sub>0</jats:sub>) by quenching the<jats:italic>Φ</jats:italic> <jats:sub>0</jats:sub>-period Aharonov–Bohm oscillation. It is found that the helical spin texture induced <jats:italic>π</jats:italic> Berry phase is key to such weak antilocalization behavior with zero return probability at <jats:italic>Φ</jats:italic> = 0. In contrast, the oscillation for the trivial edge states may exhibit either weak localization or antilocalization depending on the strength of the spin-orbit coupling, which has finite return probability at <jats:italic>Φ</jats:italic> = 0. Our results provide an effective way for the identification of the helical edge states. The predicted signature is stabilized by the time-reversal symmetry so that it is robust against disorder and does not require any fine adjustment of system.</jats:p>

<jats:p>High fidelity single shot qubit state readout is essential for many quantum information processing protocols. In superconducting quantum circuit, the qubit state is usually determined by detecting the dispersive frequency shift of a microwave cavity from either transmission or reflection. We demonstrate the use of constructive interference between the transmitted and reflected signal to optimize the qubit state readout, with which we find a better resolved state discrimination and an improved qubit readout fidelity. As a simple and convenient approach, our scheme can be combined with other qubit readout methods based on the discrimination of cavity photon states to further improve the qubit state readout.</jats:p>