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Silber I, Mathimalar S, Mangel I, Nayak AK, Green O, Avraham N, Beidenkopf H, Feldman I, Kanigel A, Klein A, Goldstein M, Banerjee A, Sela E, Dagan Y. Two-component nematic superconductivity in 4Hb-TaS 2. Nat Commun 2024; 15:824. [PMID: 38280890 PMCID: PMC10821864 DOI: 10.1038/s41467-024-45169-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2022] [Accepted: 01/15/2024] [Indexed: 01/29/2024] Open
Abstract
Most superconductors have an isotropic, single component order parameter and are well described by the standard (BCS) theory for superconductivity. Unconventional, multiple-component superconductors are exceptionally rare and are much less understood. Here, we combine scanning tunneling microscopy and angle-resolved macroscopic transport for studying the candidate chiral superconductor, 4Hb-TaS2. We reveal quasi-periodic one-dimensional modulations in the tunneling conductance accompanied by two-fold symmetric superconducting critical field. The strong modulation of the in-plane critical field, Hc2, points to a nematic, unconventional order parameter. However, the imaged vortex core is isotropic at low temperatures. We suggest a model that reconciles this apparent discrepancy and takes into account previously observed spontaneous time-reversal symmetry breaking at low temperatures. The model describes a competition between a dominating chiral superconducting order parameter and a nematic one. The latter emerges close to the normal phase. Our results strongly support the existence of two-component superconductivity in 4Hb-TaS2 and can provide valuable insights into other systems with coexistent charge order and superconductivity.
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Affiliation(s)
- I Silber
- School of Physics and Astronomy, Tel - Aviv University, Tel Aviv, 69978, Israel
| | - S Mathimalar
- Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot, Israel
| | - I Mangel
- Physics Department, Technion-Israel Institute of Technology, Haifa, 32000, Israel
| | - A K Nayak
- Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot, Israel
| | - O Green
- School of Physics and Astronomy, Tel - Aviv University, Tel Aviv, 69978, Israel
| | - N Avraham
- Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot, Israel
| | - H Beidenkopf
- Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot, Israel
| | - I Feldman
- Physics Department, Technion-Israel Institute of Technology, Haifa, 32000, Israel
| | - A Kanigel
- Physics Department, Technion-Israel Institute of Technology, Haifa, 32000, Israel
| | - A Klein
- Department of Physics, Faculty of Natural Sciences, Ariel University, Ariel, 40700, Israel
- Department of Chemical Physics, The Weizmann Institute of Science, Rehovot, 76100, Israel
| | - M Goldstein
- School of Physics and Astronomy, Tel - Aviv University, Tel Aviv, 69978, Israel
| | - A Banerjee
- Department of Physics, Ben-Gurion University of the Negev, Beer-Sheva, 84105, Israel
| | - E Sela
- School of Physics and Astronomy, Tel - Aviv University, Tel Aviv, 69978, Israel
| | - Y Dagan
- School of Physics and Astronomy, Tel - Aviv University, Tel Aviv, 69978, Israel.
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Chaudhary S, Panda JJ, Mundlia S, Mathimalar S, Ahmedof A, Raman KV. A low noise cryogen-free scanning tunneling microscope-superconducting magnet system with vacuum sample transfer. Rev Sci Instrum 2021; 92:023906. [PMID: 33648090 DOI: 10.1063/5.0041037] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/18/2020] [Accepted: 01/15/2021] [Indexed: 06/12/2023]
Abstract
Imaging atomically resolved surfaces and performing spectroscopy of exotic surfaces at cryogenic temperature in the presence of the magnetic field is an engineering challenge. Additionally, performing these measurements in an all-cryogen-free environment compounds the above complexity due to the associated vibration and acoustic noise generated by the running of cryogenic cold heads. We here report successful integration of a cryogen-free scanning tunneling microscope (STM) with a cryogen-free superconducting vector-magnet, connected to an ultra-high vacuum cluster assembly for in situ sample transfer. We present details of the integration involving vibration and electrical noise isolation procedures allowing for operation of the STM at extremely low noise levels below 30 fA/Hz during normal operations of the complete vacuum-line assembly with multiple turbomolecular pumps. We demonstrate the above STM capability at cryogenic temperature and in the presence of the magnetic field through atomic resolution imaging of graphite and thin films of gold on the mica substrate transferred in situ to the STM chamber. We also demonstrate spectroscopy signatures of the superconducting gap in MgB2 thin films. The design of our in-house customized cluster-vacuum-line assembly provides unsought opportunities in continuous uninterrupted imaging of ultra-clean in-vacuum grown surfaces without the need for cryogenic refills in either the STM or the magnet.
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Affiliation(s)
| | | | - Suman Mundlia
- Tata Institute of Fundamental Research, Hyderabad 500107, India
| | - S Mathimalar
- Tata Institute of Fundamental Research, Hyderabad 500107, India
| | - Aathif Ahmedof
- Tata Institute of Fundamental Research, Hyderabad 500107, India
| | - Karthik V Raman
- Tata Institute of Fundamental Research, Hyderabad 500107, India
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Singh A, Pal S, Surdi H, Prabhu SS, Mathimalar S, Nanal V, Pillay RG, Döhler GH. Carbon irradiated semi insulating GaAs for photoconductive terahertz pulse detection. Opt Express 2015; 23:6656-6661. [PMID: 25836882 DOI: 10.1364/oe.23.006656] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
We report here a photoconductive material for THz detection with sub-picosecond carrier lifetime made by C(12) (Carbon) irradiation on commercially available semi-insulating (SI) GaAs. We are able to reduce the carrier lifetime of SI-GaAs down to sub-picosecond by irradiating it with various irradiation dosages of Carbon (C(12)) ions. With an increase of the irradiation dose from ~10(12) /cm(2) to ~10(15) /cm(2) the carrier lifetime of SI-GaAs monotonously decreases to 0.55 picosecond, whereas that of usual non-irradiated SI-GaAs is ~70 picosecond. This decreased carrier lifetime has resulted in a strong improvement in THz pulse detection compared with normal SI-GaAs. Improvement in signal to noise ratio as well as in detection bandwidth is observed. Carbon irradiated SI-GaAs appears to be an economical alternative to low temperature grown GaAs for fabrication of THz devices.
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