Article
Materials Science, Multidisciplinary
Haicheng Lin, Wantong Huang, Gautam Rai, Yuguo Yin, Lianyi He, Qi-Kun Xue, Stephan Haas, Stefan Kettemann, Xi Chen, Shuai-Hua Ji
Summary: We directly observe the quantum many-body states in the BCS-BEC crossover regime in a FeSe monolayer thin film using spatially resolved scanning tunneling spectra. The crossover is driven by the shift of band structure relative to the Fermi level, and a theoretical calculation based on a two-band model qualitatively reproduces the measured spectra. Additionally, the observed Zeeman splitting of the quasiparticle states is consistent with the characteristics of a condensate. Our work provides a pathway to study exotic states of BCS-BEC crossover in two-dimensional crystalline materials at the atomic scale.
Article
Physics, Multidisciplinary
J. C. Obeso-Jureidini, G. A. Dominguez-Castro, E. Neri, R. Paredes, V Romero-Rochin
Summary: This study demonstrates the universality of long-distance behavior for two-body density correlation functions and Cooper-pair probability density in a balanced mixture of a two-component Fermi gas during the Bardeen-Cooper-Schrieffer (BCS)-Bose-Einstein condensate (BEC) smooth transition. Numerical results show that these two-body quantities exhibit exponential decay with respect to the chemical potential and the low-energy behavior of the gap. A general expression is derived for the two-body distributions, which holds for various features of finite-range potentials.
NEW JOURNAL OF PHYSICS
(2023)
Article
Physics, Multidisciplinary
Jing Zhou, Tingting Shi, Xia-Ji Liu, Hui Hu, Wei Zhang
Summary: We investigate the crossover from the BCS regime to the BEC regime in an anisotropic trapped quantum gas of ultracold fermionic atoms. By using a two-dimensional Hamiltonian with renormalized interactions and extending the Gaussian pair fluctuation theory to quasi-two-dimensional systems, we explore the effects of reduced dimensionality and Gaussian fluctuations on Fermi superfluidity at zero temperature. Our results are in good agreement with recent experiments on Li-6 atomic gases.
NEW JOURNAL OF PHYSICS
(2023)
Article
Physics, Multidisciplinary
Senne Van Loon, Jacques Tempere, Hadrien Kurkjian
Summary: This study investigates the fermionic quasiparticle spectrum in a zero-temperature superfluid Fermi gas and how it is affected by different disintegration processes. In addition to the disintegration by emission of a collective boson, the study also considers disintegration events where three quasiparticles are emitted. It is found that both disintegration processes are described by a t-matrix self-energy and that the quasiparticle spectrum is heavily distorted near the 1 -> 3 disintegration threshold at strong coupling.
Article
Physics, Applied
Akinori Kamiyama, Masahiro Matsuura, John N. Moore, Takaaki Mano, Naokazu Shibata, Go Yusa
Summary: By using pump-probe stroboscopic confocal microscopy and spectroscopy, the dynamics of trions and the fractional quantum Hall edge on a timescale of 1 ps are demonstrated. The propagation of the quantum Hall edge state excited by a voltage pulse is detected through temporal changes in reflectance. This ultra-fast stroboscope measurement enables the distinction between different types of edge excitations and allows for the study of the dynamics of quantum Hall edges.
APPLIED PHYSICS LETTERS
(2023)
Article
Physics, Multidisciplinary
S. N. Klimin, J. Tempere, T. Repplinger, H. Kurkjian
Summary: This study investigates collective excitations in the superfluid state of Fermi condensed charged gases. It examines the dispersion and damping of collective excitations at nonzero temperatures, and considers the coexistence and interaction of different branches of collective excitations: plasma oscillations, pair-breaking Higgs modes, and Carlson-Goldman phonon-like excitations. The path integral methods for superfluid Fermi gases and for Coulomb gas are combined into a unified formalism to account for plasmonic modes. The spectra of collective excitations are determined in two ways: from the spectral functions and from the complex poles of the fluctuation propagator. A resonant avoided crossing of different modes is shown, accompanied by resonant enhancement of the response provided by the pair-breaking modes due to their interaction with plasma oscillations, which may facilitate the experimental observation of the pair-breaking modes.
NEW JOURNAL OF PHYSICS
(2023)
Article
Materials Science, Multidisciplinary
Dan Phan, Andrey V. Chubukov
Summary: Although significant research has focused on the Higgs mode in superconducting systems, there is limited study on the dispersion and width of the Higgs peak, which can be observed through spectroscopic measurements. This study examines the behavior of the Higgs mode in a two-dimensional neutral fermionic superfluid, specifically during the crossover from Bardeen-Cooper-Schrieffer to Bose-Einstein condensation behavior. The analysis reveals that the Higgs susceptibility exhibits a pole in the lower half plane of frequency for positive dressed chemical potential and leads to a well-defined peak in spectroscopic probes.
Article
Materials Science, Multidisciplinary
M. E. Ateuafack, G. D. Kemlekeu, M. G. Akumbom, J. T. Diffo, V. B. Mborong, L. C. Fai
Summary: The negative impact of population imbalance on the superfluid density was observed in the weak coupling regime. Furthermore, it was found that the system robustly resisted population imbalance in the strong coupling regime.
RESULTS IN PHYSICS
(2021)
Article
Physics, Multidisciplinary
Xiang-Chuan Yan, Da-Li Sun, Lu Wang, Jing Min, Shi-Guo Peng, Kai-Jun Jiang
Summary: In this study, characteristic atomic behaviors in the BECBCS crossover were observed by tuning the magnetic field across the Feshbach resonance, revealing a non-monotonic anisotropic expansion and indication of bimodal distribution in a condensate of diatomic molecules. The measurement of three-body recombination atom loss also supported previous experiments and theoretical predictions, showing that the maximum atom loss occurs in the BEC limit and gets closer to the Feshbach resonance at lower atom temperatures. This work provides a controllable platform for studying strongly interacting Fermi gases.
Article
Physics, Condensed Matter
Eloisa Cuestas, Ana P. Majtey
Summary: By incorporating the effect of a trap with characteristic energy given by the Fermi temperature TF into a two-channel model for Feshbach resonances, the study successfully reproduces the binding energy of ultracold molecules and closed-channel fraction Z in atomic Fermi gases. The results are consistent with the expected behavior of Z proportional to root TF at unitarity, as well as recent measurements of the Z dependency on TF, providing valuable insights for future experiments.
JOURNAL OF PHYSICS-CONDENSED MATTER
(2021)
Article
Physics, Applied
Giancarlo Calvanese Strinati
Summary: The realization of BCS-BEC crossover with ultra-cold Fermi gases is a significant scientific achievement. The comparison between theory and experiment is essential, and recent advances using diagrammatic approach improved the widely used t-matrix method, leading to a better description of certain physical phenomena.
PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS
(2023)
Article
Mathematics, Applied
Boling Guo, Yitong Pei
Summary: In this paper, the existence of time-periodic solutions to the time-dependent Ginzburg-Landau (TDGL) equations in the BCS-BEC crossover scenario is demonstrated by employing the Leray-Schauder fixed point theorem.
APPLICABLE ANALYSIS
(2022)
Article
Physics, Applied
Jun Tokimoto, Shunji Tsuchiya, Tetsuro Nikuni
Summary: Josephson oscillation is a phenomenon in superfluids where supercurrent tunnels through a potential barrier, resulting in the oscillation of population difference. Transition from Josephson oscillation to self-trapping has been observed in experiments of Bose-condensed gas. We numerically analyze normal Josephson oscillations and self-trapping in a Fermi superfluid gas across the BCS-BEC crossover.
JOURNAL OF LOW TEMPERATURE PHYSICS
(2022)
Article
Physics, Condensed Matter
Luca Dell'Anna, Federico De Bettin, Luca Salasnich
Summary: We investigate the three-dimensional BCS-BEC crossover in the presence of a Rabi coupling, which strongly affects several properties of the system. We determine the critical interaction strength and calculate the effect of the Rabi coupling on the critical temperature of the superfluid-to-normal phase transition using different theoretical schemes.
Article
Physics, Applied
R-L Qu, K. Li, Y-X Bai, H-S Zhao
Summary: By solving the finite-temperature Bogoliubov-de Gennes equations, we studied the temperature-dependent behavior of dark solitons in superfluid Fermi gases along the BCS-BEC crossover. The notch depth of the soliton density distribution decreases with increasing temperature across the crossover. The temperature-dependent behavior of the notch depth differs distinctly from the BCS regime to the BEC regime, showing a concave, linear, and convex function in these respective regimes.
JOURNAL OF LOW TEMPERATURE PHYSICS
(2021)
Article
Physics, Condensed Matter
Y. Haga, P. Opletal, Y. Tokiwa, E. Yamamoto, Y. Tokunaga, S. Kambe, H. Sakai
Summary: Single crystals of the unconventional superconductor UTe2 have been grown under different conditions, resulting in different superconducting transition temperatures and normal state properties. The stoichiometry of the samples has been accurately characterized, with the superconducting samples being nearly stoichiometric and the non-superconducting sample deviating significantly. The superconducting UTe2 exhibits partially gapped large density of states in the normal state, while the non-superconducting sample is characterized by a relatively large electronic specific heat.
JOURNAL OF PHYSICS-CONDENSED MATTER
(2022)
Article
Physics, Multidisciplinary
Jake Ayres, Matija Culo, Jonathan Buhot, Bence Bernath, Shigeru Kasahara, Yuji Matsuda, Takasada Shibauchi, Antony Carrington, Sven Friedemann, Nigel E. Hussey
Summary: In this study, the authors investigate the resistive properties of sulfur-doped FeSe under applied pressure and find evidence of a decoupling of electronic nematicity and magnetic fluctuations in this system.
COMMUNICATIONS PHYSICS
(2022)
Article
Physics, Multidisciplinary
Masaya Tsujii, Kousuke Ishida, Shigeyuki Ishida, Yuta Mizukami, Akira Iyo, Hiroshi Eisaki, Takasada Shibauchi
Summary: Recent studies on heavily hole-doped iron-based superconductor RbFe2As2 have shown the emergence of novel electronic nematicity along the Fe-As direction, different from the usual nematicity found in BaFe2As2 and related materials. Measurements on Ba1-xRbxFe2As2 superconductors reveal deviations from Fermi liquid behavior near optimal composition, potentially linked to hidden nematic quantum criticality, and increased electron correlations with Rb content near heavily hole-doped end, indicative of Mott physics near 3d(5) electron configuration in iron-based superconductors.
JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN
(2022)
Article
Physics, Multidisciplinary
Shota Suetsugu, Yuzuki Ukai, Masaki Shimomura, Masashi Kamimura, Tomoya Asaba, Yuichi Kasahara, Nobuyuki Kurita, Hidekazu Tanaka, Takasada Shibauchi, Joji Nasu, Yukitoshi Motome, Yuji Matsuda
Summary: Researchers have found that the Kitaev quantum spin liquid on the two-dimensional honeycomb lattice undergoes a phase transition at intense magnetic fields, which may be a weak first-order transition. This transition affects the thermal Hall conductance of the topological state.
JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN
(2022)
Article
Physics, Multidisciplinary
Petr Opletal, Hironori Sakai, Yoshinori Haga, Yoshifumi Tokiwa, Etsuji Yamamoto, Shinsaku Kambe, Yo Tokunaga
Summary: We studied the physical properties of a single crystal of uranium telluride U7Te12. It was found that U7Te12 crystallizes in a hexagonal structure with three different crystallographic uranium sites. The paramagnetic moments were estimated to be approximately 1 µB per uranium site assuming a uniform moment on all the sites. A ferromagnetic phase transition occurred at TC = 48 K, with a sharp increase in in-plane magnetization while the out-of-plane component did not increase significantly. Further below TC under field-cooling conditions, the out-of-plane component increased rapidly around T* = 26 K, while the in-plane component showed little change at T*. Specific heat measurement indicated a crossover suggesting a reorientation of ordering moments or successive magnetic ordering of the multiple uranium sites.
JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN
(2023)
Article
Multidisciplinary Sciences
Kohei Matsuura, Masaki Roppongi, Mingwei Qiu, Qi Sheng, Yipeng Cai, Kohtaro Yamakawa, Zurab Guguchia, Ryan P. Day, Kenji M. Kojima, Andrea Damascelli, Yuichi Sugimura, Mikihiko Saito, Takaaki Takenaka, Kota Ishihara, Yuta Mizukami, Kenichiro Hashimoto, Yilun Gu, Shengli Guo, Licheng Fu, Zheneng Zhang, Fanlong Ning, Guoqiang Zhao, Guangyang Dai, Changqing Jin, James W. Beare, Graeme M. Luke, Yasutomo J. Uemura, Takasada Shibauchi
Summary: Iron-chalcogenide superconductors FeSe1-xSx have unique electronic properties and the nature of superconductivity with nematicity is important for understanding unconventional superconductivity. Recent experiments show that the superconducting state in FeSe1-xSx breaks time-reversal symmetry and exhibits ultranodal pair state. The presence of broken TRS and suppressed superfluid density suggests the existence of two different superconducting states separated by the nematic critical point.
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
(2023)
Article
Multidisciplinary Sciences
M. Roppongi, K. Ishihara, Y. Tanaka, K. Ogawa, K. Okada, S. Liu, K. Mukasa, Y. Mizukami, Y. Uwatoko, R. Grasset, M. Konczykowski, B. R. Ortiz, S. D. Wilson, K. Hashimoto, T. Shibauchi
Summary: The recently discovered kagome superconductors AV(3)Sb(5) (A = K, Rb, Cs) exhibit unusual CDW orders with symmetry breaking. The symmetry of the superconductivity inside the CDW phase is still unknown. Impurity effects in CsV3Sb5 were studied using electron irradiation as a phase-sensitive probe, and the results indicate that CsV3Sb5 is a non-chiral, anisotropic s-wave superconductor with no sign change.
NATURE COMMUNICATIONS
(2023)
Article
Multidisciplinary Sciences
Kota Ishihara, Masaki Roppongi, Masayuki Kobayashi, Kumpei Imamura, Yuta Mizukami, Hironori Sakai, Petr Opletal, Yoshifumi Tokiwa, Yoshinori Haga, Kenichiro Hashimoto, Takasada Shibauchi
Summary: Evidence consistent with chiral B-3u+iA(u) spin-triplet superconductivity in UTe2 is found through magnetic penetration depth measurements.
NATURE COMMUNICATIONS
(2023)
Article
Multidisciplinary Sciences
Yoshito Watanabe, Atsushi Miyake, Masaki Gen, Yuta Mizukami, Kenichiro Hashimoto, Takasada Shibauchi, Akihiko Ikeda, Masashi Tokunaga, Takashi Kurumaji, Yusuke Tokunaga, Taka-hisa Arima
Summary: The magnetic phase diagram and double dome structure of a S = 3/2 quantum antiferromagnet is studied, with the importance of different types of magnetic Bose-Einstein condensates discussed. The effects of randomness induced by quenched disorder on the system are also investigated.
NATURE COMMUNICATIONS
(2023)
Article
Multidisciplinary Sciences
Tomoya Asaba, Lang Peng, Takahiro Ono, Satoru Akutagawa, Ibuki Tanaka, Hinako Murayama, Shota Suetsugu, Aleksandar Razpopov, Yuichi Kasahara, Takahito Terashima, Yuhki Kohsaka, Takasada Shibauchi, Masatoshi Ichikawa, Roser Valenti, Shin-ichi Sasa, Yuji Matsuda
Summary: We have discovered a simple method to fabricate atomic-scale wires with various arrangements, including stripes, X-junctions, Y-junctions, and nanorings. These wires are grown on graphite substrates by pulsed-laser deposition and have precise dimensions. Our findings suggest that nonequilibrium reaction-diffusion processes are crucial for the formation of atomic patterns, and this discovery opens up new possibilities for constructing quantum networks at the atomic scale.
Article
Multidisciplinary Sciences
M. Culo, S. Licciardello, K. Ishida, K. Mukasa, J. Ayres, J. Buhot, Y. T. Hsu, S. Imajo, M. W. Qiu, M. Saito, Y. Uezono, T. Otsuka, T. Watanabe, K. Kindo, T. Shibauchi, S. Kasahara, Y. Matsuda, N. E. Hussey
Summary: The authors present high-field magnetotransport measurements of FeSe1-xSx and FeSe1-xTex, which show a broad quantum vortex liquid regime. This indicates the presence of a quantum vortex liquid state and the destruction of the Abrikosov lattice by intense quantum fluctuations at very low temperatures.
NATURE COMMUNICATIONS
(2023)
Article
Physics, Multidisciplinary
Yuta Mizukami, Masahiro Haze, Ohei Tanaka, Kohei Matsuura, Daiki Sano, Jakob Boeker, Ilya Eremin, Shigeru Kasahara, Yuji Matsuda, Takasada Shibauchi
Summary: The authors use FeSe1-xSx to investigate the evolution of the superconducting state in the BCS-BEC crossover regime and observe the multiband nature of the crossover, as well as a suppression of the nematic order upon S-substitution. Recent experiments suggest that investigations into the BCS-BEC crossover may be possible using strongly correlated systems, in addition to ultracold atomic systems.
COMMUNICATIONS PHYSICS
(2023)
Article
Physics, Multidisciplinary
Zhongyu Yu, Koya Nakamura, Kazuya Inomata, Xiaoling Shen, Taketora Mikuri, Kohei Matsuura, Yuta Mizukami, Shigeru Kasahara, Yuji Matsuda, Takasada Shibauchi, Yoshiya Uwatoko, Naoki Fujiwara
Summary: The study of FeSe has led to the discovery of spin fluctuations originating from Bogoliubov Fermi surfaces in the superconducting state.
COMMUNICATIONS PHYSICS
(2023)
Article
Physics, Multidisciplinary
K. Ishihara, M. Kobayashi, K. Imamura, M. Konczykowski, H. Sakai, P. Opletal, Y. Tokiwa, Y. Haga, K. Hashimoto, T. Shibauchi
Summary: The exotic superconducting properties of the paramagnetic spin-triplet superconductor candidate UTe2, such as extremely high upper critical field and possible chiral superconducting states, have attracted significant attention. This study focuses on the thermodynamic critical field Hc, the lower critical field Hc1, and the upper critical field Hc2 at low fields of ultraclean single crystals of UTe2, providing crucial insight into its intrinsic superconducting properties. Anomalous enhancement of Hc1 values with magnetic field along the b and c axes, showing unusual low-temperature upturns, is attributed to the effect of strong Ising-like ferromagnetic fluctuations on the vortex line energy.
PHYSICAL REVIEW RESEARCH
(2023)
Article
Materials Science, Multidisciplinary
Y. Kasahara, S. Suetsugu, T. Asaba, S. Kasahara, T. Shibauchi, N. Kurita, H. Tanaka, Y. Matsuda
Summary: This study investigates the topological properties of α-RuCl3 material through the measurement of thermal Hall conductivity, revealing the relationship between the half-integer quantum thermal Hall effect, longitudinal thermal conductivity, and Neel temperature. The quantization phenomenon is found to be significantly affected by impurity scatterings and non-Kitaev interactions.
