Bulletin of the American Physical Society
APS March Meeting 2023
Volume 68, Number 3
Las Vegas, Nevada (March 5-10)
Virtual (March 20-22); Time Zone: Pacific Time
Session B27: Superconductivity:Low_Temp_1 |
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Sponsoring Units: DCMP Chair: Mainak Pal, University of Florida Room: Room 219 |
Monday, March 6, 2023 11:30AM - 11:42AM |
B27.00001: Characterization of superconductivity in doped Ga:Ge thin films grown by molecular beam epitaxy Aurelia M Brook, Patrick J Strohbeen, Javad Shabani, Melissa E Mikalsen, Elifnaz Önder, Lukas J Baker, Bassel H Elfeky Germanium (Ge) has emerged as a promising candidate for housing quantum computing architectures through superconducting qubits [1]. As a group IV semiconductor, it has been shown to undergo a metal-insulator transition when doped with gallium (Ga) [2] and at high enough concentrations attainable by ion implantation, superconductivity is observed [3]. In particular, we examine this phenomenon when the films are grown through molecular beam epitaxy (MBE). We measure an increase in TC from 0.8K-2K and BC from 50mT to 250mT suggestive of strong confinement effects. Enhanced in-plane BC up to 1.3T is observed and will be discussed in the context of Ginzburg-Landau theory. Finally, future use in quantum information circuitry will be briefly discussed. |
Monday, March 6, 2023 11:42AM - 11:54AM |
B27.00002: Axis thermal expansion switching in transition-metal zirconides superconductors TrZr2 by tuning the c/a ratio Hiroto Arima, Md R Kasem, Yoshikazu Mizuguchi CuAl2-type CoZr2 (space group #140) has been reported to exhibit superconducting transition at TC ~ 5.2 K and c-axis negative thermal expansion (NTE) from up to 570 K[1]. To explore CuAl2-type superconducters with NTE, we synthesized NiZr2, (Co,Rh,Ir)Zr2, and (Co,Ni,Cu,Rh,Ir)Zr2 and conducted X-ray powder diffraction and magnetization mesurement for them. The heat expands lattice constants a and c of NiZr2, which is positive thermal expansion (PTE). Conversely, although a-axes of (Co,Rh,Ir)Zr2 and (Co,Ni,Cu,Rh,Ir)Zr2 exhibit PTE, those of c-axes shrink with incresing temperature indicating NTE. We made the plot of the c-axis thermal expansion amplitude as a function of the ratio of lattice c and a (c/a) for the examined compounds and related TrZr2, and we reveal that the c-axis thermal exoansion is controllable by tuning c/a throhgh the Tr-site substitusion. |
Monday, March 6, 2023 11:54AM - 12:06PM |
B27.00003: In-situ growth and synchrotron diffraction studies of the structural properties of superconducting TixOy thin films Merve Baksi Understanding and enhancing high-Tc superconductivity in materials remains an active area of scientific and technological interest. Recent studies of thin films of the binary oxide TixOy have revealed higher superconducting transition temperatures than the bulk. To further understand the mechanisms for this enhancement, we have explored the effect of the growth conditions on the transport and structural properties of TixOy films that are grown on (0001)-Al2O3 substrates using molecular beam epitaxy. We observe that carefully tuning the ratio between Ti flux rate and oxygen partial pressure leads to a diverse range of structural phases and electronic states. Moreover, a combination of synthesis and in-situ synchrotron X-ray diffraction measurements to map out the structure-property relationship reveal that the metallicity of the films arises from the formation of the oxygen-poor cubic c-TiO phase. The superconducting γ − Ti3O5 Magneli phase is found to nucleate on the cubic TiO buffer. A correlation is observed between the strain state of γ − Ti3O5 phase and the superconducting Tc with Tc increasing with film thickness as strain is relaxed. We observe a maximum Tc onset of 7.5 K for 33 nm thick films under optimized growth conditions. These results have implications for understanding the role of strain and electronic and structural disorder in superconducting oxides. |
Monday, March 6, 2023 12:06PM - 12:18PM |
B27.00004: Nanoscale lattice and chemical composition measurements of superconducting Nb3Sn films using scanning transmission electron microscopy Zhaslan Baraissov, Zeming Sun, Yu-Tsun Shao, Nathan S Sitaraman, Tomas A Arias, Matthias U Liepe, David A Muller Modern-day superconducting radio-frequency (SRF) cavities for particle accelerators are made from Nb, and after decades of development their RF performance is approaching the theoretical limit for Nb. One of the most attractive materials to replace Nb is Nb3Sn, because of its higher superheating field and critical temperature. However, due to its intrinsic smaller coherence length, this alloy is more sensitive to degradation of superconducting properties from defects such as tin deficiency and strain. Here, we use scanning transmission electron microscopy (STEM) to examine these defects at nanoscale. By performing the Energy Dispersive X-ray Spectroscopy (EDX) analysis, we identify tin-deficient regions in the film. Samples from two growth methods - vapor diffusion and electrochemical synthesis - are analyzed, and the stoichiometric differences between these methods are found. Next, in order to measure the lattice parameter of the crystal, we performed 4-dimensional STEM maps, where the entire diffraction pattern is collected at each scanning position. Furthermore, by combining the information from the zero-order Laue zone (FOLZ) and higher-order Laue zones (HOLZ) we develop a method to calculate the full 3-dimensional strain tensor. Finally, we determine a correlation between the strain and chemical composition. We highlight the use of our defect analysis to improve the Nb3Sn SRF cavity development. |
Monday, March 6, 2023 12:18PM - 12:30PM |
B27.00005: Experimental signature of spin-triplet superconductors Chih-Chieh Chiang, Hung-Chieh Lee, Shi-Chieh Lin, Danru Qu, Ming-Wen Chu, Chii-Dong Chen, C. L. Chien, Ssu-Yen Huang Spin-triplet superconductors have attracted great attention for exploring Majorana Fermions and developing quantum computing. Superconductors with inversion crystal symmetry must be either spin-singlet with even gap symmetry (such as Nb) or spin-triplet with odd gap symmetry (such as β-Bi2Pd). However, the broken crystal inversion symmetry in noncentrosymmetric superconductors compels an admixture of singlet and triplet pairing states. The unusual material BiPd can form both the centrosymmetric superconductor γ-BiPd (TC = 3.3 K) and the noncentrosymmetric superconductor α-BiPd (TC = 3.7 K), thus allowing BiPd to reveal the signatures of different pairing states. We report the discovery of multiple and single unconventional critical field-temperature phase diagrams in α-BiPd and β-Bi2Pd, respectively, but only a single-component BCS-type phase diagram in γ-BiPd. We further perform a phase-sensitive experiment to confirm the singlet and triplet pairing states. We observe the quantization of half-magnetic and integer-magnetic fluxes in mesoscopic rings that provide conclusive evidence for triplet pairing in centrosymmetric β-Bi2Pd, singlet pairing in centrosymmetric γ-BiPd, and the admixture of singlet-triplet pairing in α-BiPd. Our critical field and phase-sensitive measurements identify triplet pairing superconductors and the constraints of crystal symmetry on the pairing states, which is essential for the exploration of triplet superconductors and their quantum properties. |
Monday, March 6, 2023 12:30PM - 12:42PM |
B27.00006: Observation of Superconductivity in Li-intercalated SnSe2 Single Crystals Daniel T Duong We have successfully synthesized layered SnSe2 single crystals through the vapor transportation method. Lithium was further intercalated into SnSe2 using the electrochemical gating method. The LixSnSe2 single crystals were characterized through magnetization and resistivity measurements down to 1.9 K, which reveal diamagnetism and resistivity drop below Tc ~ 6 K. These characteristics can be attributed to the onset of superconductivity. The physical properties of both unintercalated (x = 0) and intercalated (x ≠ 0) LixSnSe2 will be reported. |
Monday, March 6, 2023 12:42PM - 12:54PM |
B27.00007: Molecular Beam Epitaxy of Superconducting In-Doped Tin Telluride (Sn1-xInxTe) Antonio Gonzalez, Athby H Al-Tawhid, Sam J Poage, Shalinee Chikara, Kaveh Ahadi Topological crystalline insulators (TCI) such as Tin Telluride (SnTe), have garnered great interest due to their unique magnetotransport properties and potential applications in novel electronic devices. More recently, it has been shown that a superconducting state is induced in SnTe by introducing indium as a dopant, (Sn1-xInxTe). This begs the question of whether this compound is a candidate as a superconducting TCI. We have grown In-doped SnTe on BaF2(111) substrates in a chalcogenide molecular beam epitaxy system. XRD measurements confirm high quality single phase SnTe. By increasing the indium concentration, we observe that the critical temperature of superconductivity increases and the carrier mobility is systematically suppressed. We also observe quantum oscillations in dilute samples with high mobility. These results shed light on the nature of the superconducting transition in Sn1-xInxTe. |
Monday, March 6, 2023 12:54PM - 1:06PM |
B27.00008: Superconductivity in Ir- and Os-based Laves compounds Karolina Górnicka, Tomasz Klimczuk Laves phase compounds belong to the class of Frank – Kasper phases showing topologically close-packed structures. They are categorized primarily into three parent members: the C14 hexagonal MgZn2 – type (P63/mmc), the C15 cubic MgCu2 – type (Fd-3m) and the C36 hexagonal MgNi2 – type structures (P63/mmc). Motivated to describing Ir- and Os-based Laves superconductors, we synthesized and tested ROs2 (R = Lu, Y, Sc) and AIr2 (A = Ca, Sr) materials. The detailed characterization of the superconductivity and electronic structure of these intermetallic compounds are of great interest mainly because of the expected enhanced SOC behavior. The spin-orbit coupling has an influence on the several superconducting parameters such as the electronic density of states (DOS) at the Fermi level, the electron-phonon coupling parameter λ and, the value of superconducting critical temperature Tc. |
Monday, March 6, 2023 1:06PM - 1:18PM |
B27.00009: Stress-induced structural changes in Nb thin film for superconducting qubits Jaeyel Lee, ZuHawn Sung, Akshay A Murthy, Anna Grassellino, Alexander Romanenko We report analysis of stress-induced omega (ω) phase transition in ~170 nm thick Nb thin films on Si for superconducting qubits using transmission electron microscopy (TEM) [1]. The Nb thin film exhibits {112} <111> deformation twins on the film surface, indicating that the Nb thin film is under internal stress beyond the yield strength of Nb. Also, the formation of omega (ω) phase is associated with the {112} <111> deformation twin boundaries, which is consistent with other metals such as Ta or Ti alloys. The size of the omega (ω) phases varies from 10 to 150 nm, which is comparable to the coherence length of Nb in clean limit, and their volume fraction is ~1 vol.%. Density functional theory (DFT) study anticipated that the omega (ω) phase may have suppressed Tc (1-2 K) compared to bcc Nb (~9.2 K) [2]. We conclude by discussing how the omega (ω) phase may lead to decoherence in superconducting qubits through pair breaking. |
Monday, March 6, 2023 1:18PM - 1:30PM |
B27.00010: Enhancement of superconducting transition temperature in Nb/Pd bilayers upon rapid thermal hydrogenation Junjie Li, IVAN K SCHULLER, ALI C BASARAN We studied the hydrogenation effect on the superconducting properties of Nb/Pd bilayers using a modified rapid thermal annealing approach at ~4 bar of pressure and up to 400 °C temperature. Below 300 °C annealing temperatures, the superconducting transition temperature (Tc) is enhanced from 8.77 to 9.06 K and is correlated with the compression of the unit cell. At higher annealing temperatures, a weak lattice expansion occurs, and the Tc is gradually suppressed. Furthermore, the rapid thermal hydrogenation results differently depending on the substrate of Nb/Pd bilayers. For the c-cut Al2O3 substrate, the Tc reduction started at 250 °C, while for the r-cut Al2O3, this occurred at 350 °C. We associated these features with the elastic behavior of Nb film upon hydrogenation. A model is proposed based on the increase of Tc caused by the compressive stress produced by the rapid nucleation and growth of hydrides. Our discoveries provide insights into how superconductivity can be manipulated by rapid thermal hydrogenation. |
Monday, March 6, 2023 1:30PM - 1:42PM |
B27.00011: Discovery of Superconductivity in Non-centrosymmetric Semimetal LaRhGe3 Mohamed Oudah, Samikshya Sahu, Hsiang-Hsi Kung, Niclas P Heinsdorf, Armin Schulz, Marta-Villa De Toro Sanchez, Yipeng Cai, Kenji M Kojima, Andreas P Schnyder, Bernhard Keimer, Douglas A Bonn, Alannah M Hallas LaRhGe3 crystalizes in the non-centrosymmetric space group I4mm with a strong asymmetric spin-orbit coupling (ASOC) due to containing Rh[1], which makes it a promising platform to search for spin-triplet superconductivity with time-reversal symmetry breaking (TRSB) [2]. We have grown single crystals of LaRhGe3 using a self-flux method for the first time. I present our discovery of Type-I superconductivity in LaRhGe3 with evidence from heat capacity and µSR experiments, with a critical temperature Tc of 0.385 K and critical field Hc of 2.1 mT [3]. Despite the strong ASOC in LaRhGe3, we do not detect any evidence for TRSB across Tc in LaRhGe3 in our zero-field µSR experiment. Our results are consistent with LaRhGe3 being a weak-coupling s-wave superconductor with a dominant singlet pairing. We also characterize the normal state of LaRhGe3 with temperature and field dependent electrical transport. We find a non-saturating magnetroresistance at 2 K of 800% at 9 T, which is related to electron-hole compensation in LaRhGe3. We comment on semimetallicity and topology from our band structure calculations on LaRhGe3. Finally, we find that above the onset of superconductivity, LaRhGe3 exhibits an unusual temperature dependence in its resistivity, ρ ~ T 3, suggestive of possible non-Fermi liquid behavior. To elucidate this we investigate the Raman spectra of LaRhGe3 at low temperature. |
Monday, March 6, 2023 1:42PM - 1:54PM |
B27.00012: Combinatorial exploration of the superconducting properties of BixNi1-x thin films Jihun Park, Jarryd Horn, Dylan J Kirsch, Rohit Pant, Hyeok Yoon, Sungha Baek, Suchismita Sarker, Apurva Mehta, Seunghun Lee, Richard L Greene, Johnpierre Paglione, Ichiro Takeuchi Strong spin-orbit coupling, multivalency, and the semi-metallic nature of Bi allow for a variety of unusual superconducting phenomena in elemental and compounds of Bi, such as amorphous, high-pressure, high-temperature, and topological superconductivity1–3. Recently, possible signatures of unconventional p-wave superconductivity in Bi/Ni bilayers have been reported2,3. However, spontaneous formation of the s-wave phase (Bi3Ni) has been observed at the Bi/Ni interface, possibly suggesting the p-wave superconductivity due to the proximity effect in the Bi layer rather than through an intrinsic mechanism4,5. This makes it necessary to further investigate the role of Bi in the superconductivity of the Bi–Ni binary system. In this work, we systematically studied the superconducting properties of BixNi1-x thin films via a combinatorial approach. The superconducting phase diagram reveals that additional Bi inclusion in Bi3Ni enhances the critical temperature, with improved coherence length and residual resistance ratio. Remarkably, the bulk superconductivity remains stable even in the excessively Bi-rich region despite low critical current density, implying proximity-induced superconductivity in Bi. Our work provides insights into unusual superconductivity in Bi compounds. |
Monday, March 6, 2023 1:54PM - 2:06PM Author not Attending |
B27.00013: Superconductivity and magnetism in complex mercury-based compounds Eteri Svanidze Mercury, in both elemental form and as part of compounds and amalgams has played an important role in solid-state chemistry and condensed matter physics [1-3]. However, much care must be taken both during synthesis as well as during characterization of this peculiar element and its compounds – from toxicity concerns to high chemical reactivity – these systems pose several experimental challenges. In this talk, I will showcase that, nonetheless, mercury-based materials offer unique crystallographic motifs and, as a result, peculiar physical properties [4-6]. In particular, I will concentrate on the binary compounds of mercury and lanthanide as well as actinide elements, which have so far been under investigated. Using a unique laboratory environment, we are able to synthesize single crystals of several binary phases and study their chemical and physical properties in detail. By looking at the evolution of crystallographic complexity across several series of compounds, I will discuss how intrinsic crystal chemistry affects the resultant ground states. |
Monday, March 6, 2023 2:06PM - 2:18PM |
B27.00014: Group-subgroup relationships in ternary AlB2-type compounds and their properties Dorota I Walicka The simplicity of the AlB2 structure offers a vast possibility for structural tunning, where the group-subgroup relations lead to the compounds with ZrBeSi-, CaIn2- and YPtAs-type structures. These are created by changing the structural topology of the honeycomb layers and their stacking, causing the extension of the unit cell parameter along the c axis. In this work we summarize the abundance of the compounds with the AlB2-type structure and underline the importance of an in depth understanding of their structure-property relationships. Specifically, we will focus on the Ca1-xSrxAlSi solid solutions, where we investigate the evolution of the electronic, the superconducting and the structural properties upon exchange of the interlayer atoms. |
Monday, March 6, 2023 2:18PM - 2:30PM |
B27.00015: Retaining Superconducting Phases Through Low-Temperature Pressure Quenching Trevor Bontke, Liangzi Deng, Rabin Dahal, Melissa J Gooch, Donald Rolston, Zheng Wu, Paul C. W. W Chu In the past seven years impressively high superconducting critical temperatures (Tcs) have been reported in numerous superhydride systems. Among these include Tcs which approach room temperature (RT) but require pressure exceeding 150 GPa. Retaining these enhanced Tcs while lowering or removing the applied pressure remains a significant challenge in the field. We have therefore employed a low-temperature pressure-quenching (PQing) technique to retain high-pressure induced superconducting phases in single-crystal Bi. PQing at 77 K and 4.2 K from pressures up to 26.6 GPa, we retained Bi phases with varying Tcs corresponding to Bi-II, Bi-III and Bi-V, as well as several unidentified superconducting phases. Stability testing of the retained phases at 4.2 K revealed good phase stability over time for T < 20 K. PQing displayed further utility by providing evidence for the transition of Bi-I to Bi-III via a superconducting amorphous phase and revealing a new record Tc of 9.05 K in Bi when PQed at 26.5 GPa and 4.2 K. |
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