Bulletin of the American Physical Society
APS March Meeting 2013
Volume 58, Number 1
Monday–Friday, March 18–22, 2013; Baltimore, Maryland
Session T35: HTSC: Mostly Superconductor-insulator Transition and Quantum Oscillations |
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Sponsoring Units: DMP Chair: Herbert Fotso, Georgetown University Room: 343 |
Thursday, March 21, 2013 8:00AM - 8:12AM |
T35.00001: Magnetic field driven superconductor-insulator transition in $La_{2-x}Sr_xCuO_4$ Brigitte Leridon, Johan Vanacken, Victor Moshchalkov, Baptiste Vignolle, Rajni Porwal, Ramesh Budhani The magnetic field driven superconductor/insulator transition is studied in a large variety of $La_{2-x}Sr_xCuO_4$ thin films of various Sr dopings. Temperature dependence of the resistivity down to 4.2 or 1.5 K under high pulsed magnetic field (up to 57 T) is analyzed. In particular, the existence of plateaus in the resistance versus temperature curves for given values of the magnetic field is carefully investigated. For underdoped samples, these plateaus, that are observable only in a limited range of temperatures, are shown to be associated to scaling behaviour of the resistance versus magnetic field curves, evocative of the presence of a quantum critical point. A three-dimensional (H,x,T) phase diagram is proposed, taking into account the intrinsic lamellar nature of the materials by the existence of a temperature crossover from quantum-two-dimensional to three-dimensional behavior. [Preview Abstract] |
Thursday, March 21, 2013 8:12AM - 8:24AM |
T35.00002: Magnetic-field-driven superconductor-insulator transition in underdoped La$_{2-x}$Sr$_x$CuO$_4$ Xiaoyan Shi, Ping V. Lin, Dragana Popovi\'{c}, G. Logvenov, A. Bollinger, I. Bozovic, T. Sasagawa We use magnetotransport measurements to probe the magnetic-field-driven superconductor-insulator transition in both an MBE-grown thin film ($x=0.07$ and $T_c=4$~K) and a single crystal ($x=0.06$ and $T_c=6$~K) underdoped La$_{2-x}$Sr$_{x}$CuO$_4$ samples in $T$ range of 0.1--30~K and fields up to 35~T. Surprisingly, it is possible to perform scaling analysis in both low- and high-temperature regions, where two different scaling exponents and scaling functions are obtained. These results and a detailed analysis of the temperature dependence of the resistivity suggest that a possible intermediate state exists between the superconducting state at zero field and the insulating state at high fields. This intermediate state may be related to the existence of a large region with superconducting fluctuations in ($T,H$) parameter space. Furthermore, the insulating state in high fields shares similar 2D variable-range hopping behavior as non-superconducting samples with lower doping. [Preview Abstract] |
Thursday, March 21, 2013 8:24AM - 8:36AM |
T35.00003: Penetration Depth Measurements of Electrostatically Doped High T$_{c}$ Superconductors Joe Kinney, Javier Garcia-Barriocanal, Boyi Yang, Allen Goldman The application of field effect transistor concepts to electrostatically dope strongly correlated electron systems has been the focus of intense research [C. H. Ahn et al., Rev. Mod. Phys. 78, 1185 (2006)]. In recent years, we have used this technique to successfully examine magneto-transport properties of YBa$_{2}$Cu$_{3}$O$_{7-x}$ and La$_{2}$CuO$_{4+\delta}$ [X. Leng et al., Phys. Rev. Lett. 107, 027001 (2011)] [X. Leng, et al., Phys. Rev. Lett. 108, 060074 (2012)] [J. Garcia-Barriocanal et al arXiv:1210.7458]. In the work presented here we extend this to include measurements of the penetration depth using a two coil mutual inductance technique. This probe provides an additional window into the underlying properties of the superconducting state as it is electrostatically tuned across the superconductor-insulator phase transition. [Preview Abstract] |
Thursday, March 21, 2013 8:36AM - 8:48AM |
T35.00004: Comparison of Resistivity and Superfluid Response in Thin CaYBCO Films Stanley Steers, Adam Ahmed, Thomas Lemberger Resistivity drops to negligible levels at temperatures significantly above those at which superfluid density appears for two-dimensional samples of Ca-doped YBCO. The temperature offset between the disappearance of resistivity and the onset of superfluid density, as measured by low-frequency mutual inductance experiments, depends upon $T_c$ as measured by the appearance of superfluid density, getting bigger as $T_c$ decreases and reaching a maximum as superfluid response disappears near the superconductor-insulator transition while still exhibiting a resistive transition. The offset vanishes at the maximum $T_c$. [Preview Abstract] |
Thursday, March 21, 2013 8:48AM - 9:00AM |
T35.00005: Multiple Quantum Phase Transitions in a two-dimensional superconductor Nicolas Bergeal, J. Biscaras, S. Hurand, C. Feuillet-Palma, J. Lesueur, R.C. Budhani, A. Rastogi, S. Caprara, M. Grilli We studied the magnetic field driven Quantum Phase Transition (QPT) in electrostatically gated superconducting LaTiO3/SrTiO3 interfaces [1,2]. Through finite size scaling analysis, we showed that it belongs to the (2$+$1)D XY model universality class. The system can be described as a disordered array of superconducting islands coupled by a two dimensional electron gas (2DEG). Depending on the 2DEG conductance tuned by the gate voltage, the QPT is single (corresponding to the long range phase coherence in the whole array) or double (one related to local phase coherence, the other one to the array). By retrieving the coherence length critical exponent $\nu $, we showed that the QPT can be ``clean'' or ``dirty'' according to the Harris criteria, depending on whether the phase coherence length is smaller or larger than the island size [2]. The overall behaviour is well described by a model of coupled superconducting puddles in the framework of the fermionic scenario of 2D superconducting QPT [3]. \\[4pt] [1] J. Biscaras et al, Phys. Rev. Lett. 108, 247004 (2012)\\[0pt] [2] J. Biscaras et al, arXiv:1209.6464 (2012)\\[0pt] [3] B. Spivak, et al. Phys. Rev. B 77 214523 (2008) [Preview Abstract] |
Thursday, March 21, 2013 9:00AM - 9:12AM |
T35.00006: Pseudogap and zero-bias anomaly due to fluctuation suppression of quasiparticle tunneling Andreas Glatz, Andrey Varlamov, Valerii Vinokur In this talk, I will present our study of the effect of superconducting fluctuations on the tunnel current-voltage characteristics of disordered superconducting films placed in a perpendicular magnetic field in the whole field-temperature phase diagram outside the superconducting region. This tunnel-current is experimentally accessible by STM measurements and therefore directly relevant for the interpretation of experimental results, in particular the pseudogap state. We derived a complete expression for the tunneling current (and the tunneling conductance) for arbitrary fields and temperatures and discovered an important nonlinear contribution, which appears due to dynamic fluctuation modes and results in the formation of a strong zero-bias anomaly on the scale at small voltages. At large voltages, fluctuations form a pseudogap maximum. [Preview Abstract] |
Thursday, March 21, 2013 9:12AM - 9:24AM |
T35.00007: Understanding the superconducting state in SrTiO3 interfaces: Possible two-band superconductivity J.T. Haraldsen, R.M. Fernandes, P. Woelfle, A.V. Balatasky We examine the possibility of multi-band superconductivity in SrTiO$_3$ interfaces by investigating the effects of a two-dimensional two-band model. In undoped SrTiO$_3$, one of the bands is occupied, while the upper band is empty. As the chemical potential shifts, due to doping by negative charge carriers or application of an electric field, the second band becomes occupied, giving rise to a strongenhancement of the transition temperature and a sharp feature in the gap functions, which is manifested in the local density of states spectrum. By comparing our results with tunneling experiments in Nb-doped SrTiO$_3$, we find that intra-band pairing dominates over inter-band pairing, unlikeother known multi-band superconductors. Given the similar transition temperature and band structure of LaAlO$_3$/SrTiO$_3$ heterostructures, we speculate that thesuperconductivity observed in SrTiO$_3$ interfaces may be similar in nature to that of bulk SrTiO$_3$,involving multiple bands with distinct electronic occupations. [Preview Abstract] |
Thursday, March 21, 2013 9:24AM - 9:36AM |
T35.00008: Disordered bosons in one dimension: from weak to strong randomness criticality Fawaz Hrahsheh, Thomas Vojta We investigate the superfluid-insulator quantum phase transition of one-dimensional bosons with off-diagonal disorder by means of large-scale Monte-Carlo simulations. For weak disorder, we find the transition to be in the same universality class as the superfluid-Mott insulator transition of the clean system. The nature of the transition changes for stronger disorder. Beyond a critical disorder strength, we find nonuniversal, disorder-dependent critical behavior. We compare our results to recent perturbative and strong-disorder renormalization group predictions. We also discuss experimental implication as well as extensions of our results to other systems. [Preview Abstract] |
Thursday, March 21, 2013 9:36AM - 9:48AM |
T35.00009: Scaling disparity between superconducting and pseudogap states in very low-$T_c$ Bi-2201 cuprates Vladimir Krasnov Interplay between the normal state pseudogap (PG) and superconductivity in cuprates remains a controversial issue. In this respect it is instructive to compare homologous series of cuprates with a different number of CuO planes. They have similar Fermi energies, resistivities and anisotropies, but exhibit a large variation of $T_c$. Since thermal fluctuations vanish at $T=0$, they are less significant at $T\sim T_c$ in low-$T_c$ cuprates. In this work we compare intrinsic tunneling characteristics of double-layer Bi-2212 ($T_c$=95 K) and single-layer Bi-2201 with a very low $T_c \sim 4$ K. We observe that: (i) The PG characteristics of both cuprates are identical despite a large difference in $T_c$. Thus, the PG phenomenon is universal irrespective of superconducting properties. (ii) In the low-$T_c$ Bi-2201, all superconducting characteristics scale down with $T_c$ in the same proportion as for high-$T_c$ cuprates. This leads to a dramatic disparity between superconducting ($T_c =4$ K, energy gap $< 1$ meV, $H_{c2}\sim 10$ T) and pseudogap (onset $T^* = 90-300$ K, PG energy $\sim 40$ meV, PG suppression field $H^* \sim 250$ T) characteristics in the studied low-Tc cuprate. The observed disparity of the superconducting and pseudogap scales clearly reveals their different origins. [Preview Abstract] |
Thursday, March 21, 2013 9:48AM - 10:00AM |
T35.00010: Visualizing antinodal pair decoherence in a high T$_{\mathrm{c}}$ cuprate Yang He, Yi Yin, Anjan Soumyanarayanan, Martin Zech, Tess Williams, Michael Boyer, W. D. Wise, Kamalesh Chatterjee, Takeshi Kondo, Tsunehiro Takeuchi, Hiroshi Ikuta, Eric Hudson, Jennifer Hoffman The relationship between the pseudogap phase and superconductivity in the cuprate superconductors remains mysterious. We use Fourier transform scanning tunneling spectroscopy to study the pseudogap in the cuprate superconductor Bi$_{\mathrm{2-x}}$Pb$_{\mathrm{x}}$Sr$_{2}$CuO$_{\mathrm{6+\delta}}$. We discover a new type of quasiparticle interference in the antinodal regions, presumed to be dominated by the pseudogap. Magnetic field induced spectral weight transfer shows that the pseudogap suppresses superconducting coherence but does not affect d-wave pairing at the antinode. [Preview Abstract] |
Thursday, March 21, 2013 10:00AM - 10:12AM |
T35.00011: Fermi surface geometry of YBa$_2$Cu$_4$O$_8$ Neil Harrison, Suchitra Sebastian, Gilbert Lonzarich, Fedor Balakirev, S. Sabok, B. Dabrowski Since the discovery of magnetic quantum oscillations in the underdoped high $T_{\rm c}$ cuprates, one lingering question concerns whether the Fermi surfaces of YBa$_2$Cu$_4$O$_8$ and YBa$_2$Cu$_3$O$_{6.5}$ are similar or different. To pursue this question we utilize magnetic fields extending to 100 tesla that are now available at the National High Magnetic Field Laboratory. We find magnetic fields of this strength are essential for determining the geometry of the Fermi surface of YBa$_2$Cu$_4$O$_8$ in angle-resolved measurements. Our findings enable us to clarify the origin of the Fermi surface pockets in YBa$_2$Cu$_4$O$_8$ and YBa$_2$Cu$_3$O$_{6.5}$. [Preview Abstract] |
Thursday, March 21, 2013 10:12AM - 10:24AM |
T35.00012: Quantum oscillations in YBa$_{2}$Cu$_{3}$O$_{6+\delta}$ from period-8 $d$-density wave order Zhiqiang Wang, Jonghyoun Eun, Sudip Chakravarty We consider quantum oscillation experiments in YBa$_{2}$Cu$_{3}$O$_{6+\delta}$ from the perspective of an incommensurate Fermi surface reconstruction using an exact transfer matrix method and the Pichard-Landauer formula for the conductivity. The specific density wave order responsible for reconstruction is a period-8 $d$-density wave in which the current density is unidirectionally modulated, which is also naturally accompanied by a period-4 charge order, consistent with recent nuclear magnetic resonance experiments. This scenario leads to a natural explanation as to why only oscillations from a single electron pocket of a frequency of about 500 T is observed, and a hole pocket of roughly twice the frequency as dictated by the two-fold commensurate order and the Luttinger sum rule is not observed. In contrast period-8 $d$-density wave leads to a hole pocket of roughly half the frequency of the electron pocket. The observation of this slower frequency will require higher, but not unrealistic, magnetic fields than those commonly employed. There is already some suggestion of the slower frequency in a measurement in fields as high as 85 T. [Preview Abstract] |
Thursday, March 21, 2013 10:24AM - 10:36AM |
T35.00013: Quantum oscillations, phase fluctuations and competing orders in a d-wave vortex liquid Shizhong Zhang, Sumilan Banerjee, Mohit Randeria The observation of quantum oscillations in underdoped cuprates has generated intense debate about the nature of the field-induced resistive state and its relation to the ``normal" state of high $T_c$ superconductors. Quantum oscillations suggest a Fermi liquid state at high magnetic fields $H$ and low temperatures, in contrast to the high-temperature, zero-field pseudogap state. Motivated by recent high-field heat capacity measurements, we present a theoretical analysis [1] of the electronic excitations in a vortex-liquid state, with pairing correlations that are short-ranged in both space and time. We show that this permits us to reconcile the various seemingly contradictory experimental observations. We show that phase fluctuations that give insight into the pseudogap in the high temperature classical regime also lead to a large and singular (square root of H) density of states (DOS) suppression at low temperatures. In addition, the DOS shows quantum oscillations with a period determined by a Fermi surface reconstructed by a possible competing order parameter in the vortex liquid. We also comment on possible implications of our results for thermal conductivity and $c$-axis optical conductivity in such a state. [1] S. Banerjee, S. Zhang, and M. Randeria, arXiv:1210.2466. [Preview Abstract] |
Thursday, March 21, 2013 10:36AM - 10:48AM |
T35.00014: Multi-orbital Fermi surfaces in metallic layered nickelate Masaki Uchida, K. Ishizaka, M. Sakano, R. Arita, S. Shin, Y. Tokura, P. Hansmann, A. Toschi, K. Held, X. Yang, J. Miyawaki, Y. Takata, M. Oura, A. Chainani, Y. Kaneko, O. Andersen The three-dimensional Fermi surface structure of hole-doped metallic layered nickelate Eu$_{2-x}$Sr$_x$NiO$_4$ ($x=1.1$), an important counterpart to the isostructural superconducting cuprate La$_{2-x}$Sr$_x$CuO$_4$, is investigated by energy-dependent soft-x-ray angle-resolved photoemission spectroscopy. In addition to a large cylindrical hole Fermi surface analogous to the cuprates, we observe a Gamma-centered $3z^2-r^2$-derived small electron pocket. This finding demonstrates that in the layered nickelate the $3z^2-r^2$ band resides close to the $x^2-y^2$ one in energy. The resultant multi-band feature with varying orbital character as revealed may strongly work against the emergence of the high-temperature superconductivity. [Preview Abstract] |
Thursday, March 21, 2013 10:48AM - 11:00AM |
T35.00015: Possible evidence of electron pockets beyond optimal doping James Storey, Jeffery Tallon In recent years the possibility of electron pockets in the Fermi surface of underdoped high-T$_{c}$ cuprates has become of considerable interest, spawned by quantum oscillations, Hall effect and thermopower measurements of strongly underdoped samples where stripe order is known to be present. Direct proof of their existence and location in momentum space would put significant constraints on the origin of the mysterious pseudogap and possibly the origin of superconductivity in these materials. In contrast, several Fermi surface reconstruction models predict electron pockets appearing with the onset of the pseudogap in the slightly overdoped regime before disappearing at lower dopings. We have calculated the thermopower from the resonating valence bond spin liquid model developed by Yang, Rice and Zhang, and a spin density wave model. Comparing the results with experimental data, we find evidence for electron pockets in the slightly overdoped regime. [Preview Abstract] |
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