An international workshop held at the Miramar Royal Palace in Donostia / San Sebastian on July 1619, 2018
8:30 – 09:50 
Registration 
The registration takes place inside the Miramar Palace 
09:50 – 10:00 
Welcome 
Welcome & brief talk about the Donostia International Physics Center (DIPC) 
10:00 – 10:35 
Duncan Haldane 

10:35 – 11:15 
COFFEE BREAK 

11:15 – 11:50 
Duncan Haldane 

11:50 – 12:25 
Yoichi Ando 
The spinmomentumlocked surface states of topological insulators [1] provide a fertile ground for novel quantum physics including topological superconductivity and associated Majorana fermions [2, 3]. In this talk, I will present our recent experiments to utilize stateoftheart devices based on bulkinsulating topological insulators and discuss such physics as planar Hall effect [4], nanowire quantum transport, and proximityinduced superconductivity. References: 
12:25 – 13:00 
Alberto Morpurgo 
The possibility to induce and control superconductivity at the surface of insulating materials by means of electrostatic gating is a breakthrough development that has taken place during the last decade. Probing the nature of the gateinduced superconducting state is however extremely difficult, because the superconducting surface –buried between the gate electrode and the insulating material itself– is difficult to access with most experimental probes. This is why, until now, the superconducting properties of these systems have been studied almost exclusively by means of transport measurements. Here, I will discuss our work on gate induced superconductivity on exfoliated MoS2 crystals. I will first show that superconductivity survives down to the ultimate level of an individual monolayer. I will then discuss tunneling spectroscopy measurements in the gateinduced superconducting state that we succeeded in doing using suitably nanofabricated devices. The measurements allow us to determine the density of states in the superconducting regime as a function of carrier density, and demonstrate that the superconducting state is not fully gapped. We find that throughout the carrier density range investigated, a finite subgap density of states vanishing linearly at low energy is present, indicative of unconventional superconductivity. I will point to different aspects of the measurements and discuss which indications they provide as to the nature of the superconducting state.

13:00 – 15:00 
LUNCH 
Lunch at Costa Vasca at 13:15. 
15:00 – 15:35 
Amir Yacoby 

15:35 – 16:10 
Pablo JarilloHerrero 
The understanding of stronglycorrelated quantum matter has challenged physicists for decades. Such difficulties have stimulated new research paradigms, such as ultracold atom lattices for simulating quantum materials. In this talk I will present a new platform to investigate strongly correlated physics, based on graphene moiré superlattices. In particular, I will show that when two graphene sheets are twisted by an angle close to the theoretically predicted ‘magic angle’, the resulting flat band structure near the Dirac point gives rise to a stronglycorrelated electronic system. These flat bands exhibit halffilling insulating phases at zero magnetic field, which we show to be a correlated insulator arising from electrons localized in the moiré superlattice. Moreover, upon doping, we find electrically tunable superconductivity in this system, with many characteristics similar to hightemperature cuprates superconductivity. These unique properties of magicangle twisted bilayer graphene open up a new playground for exotic manybody quantum phases in a 2D platform made of pure carbon and without magnetic field. The easy accessibility of the flat bands, the electrical tunability, and the bandwidth tunability though twist angle may pave the way towards more exotic correlated systems, such as quantum spin liquids or correlated topological insulators.

16:10 – 16:45 
Luca Chirolli 
Due to the charge neutral and localized nature of surface Majorana modes, detection schemes rely mostly on local spectroscopy or interference through the Josephson effect. In this work we consider surface corrections to the orbital magnetization in the superconducting state and study the orbital magnetic response of a twodimensional Majorana cone localized at the surface of a class DIII Topological Superconductors. For a field parallel to the surface we find that the field tilts the Majorana bands and an additional diamagnetic current appears beyond a critical threshold field $H^*$, that leads to a jump in the magnetization. The value of $H^*$ is expected to fall in the Meissner phase for highly doped small band gap Dirac insulators with oddparity superconductivity. In a spherical configuration Majorana modes always show a finite coupling to arbitrary small applied fields. Beside the tilting, a curvature induced coupling appears between occupied and empty levels that leads to a finite response. Meissner screening results in an excess diamagnetic zerofield susceptibility $propto 1/H^*$ , that acquires a universal character in finite systems that are topologically equivalent to a sphere.

16:45 – 17:15 
COFFEE BREAK 

17:15 – 17:50 
Sebastian Bergeret 
Triggered by the large number of experiments on superconductivity in the presence of spindependent fields we have developed a quasiclassical framework for studying transport properties in these systems. In this talk I will focus on both, ballistic and diffusive systems and discuss effects related to the interplay between superconductivity, intrinsic spinorbit coupling (SOC) and spinsplitting fields. I will demonstrate that these spindependent fields convert singlet pair correlations into triplet ones. This conversion manifests itself through magnetoelectric effects, in full analogy with the charge/spin coupling in normal systems. In diffusive systems, I will discuss the superconducting counterparts of the SpinHall (SHE) and the Edelstein (EE) effects, which are at the basis of the anomalous phase shift φ_{0} in the currentphase relation of Josephson junctions with SOC. I will also discuss spectral and transport properties of ballistic Josephson junctixnsand show that within the semiclassical approach all subgap, spectral and transport, properties depends only on two parameters, namely, a magnetic phase shift and a local precession axis for the spin. In particular these two parameters determine the topological state of the junction. 
17:50 – 18:10 
Judith Suter 
1e periodic microwave induced transitions in superconductingsemiconducting double island geometries
We study Cooperpair and singleelectron tunneling across a Josephson junction in a hybrid nanowirebased double quantum dot. Under microwave irradiation photon assisted tunneling is observed both in absence and presence of an axial magnetic field. Applying field demonstrates a transition from 2e to 1e periodic Coulomb blockade. The respective energy splittings at charge state degeneracies are extracted following the positions of microwaveinduced transitions as a function of frequency.
Corresponding quantum transport at finite field shows an extended zero bias conductance peak in gate voltage. Results are consistent with singleelectron tunneling between two zero energy modes residing on each side of the junction.

18:10 – 18:30 
Christian Möhle 
Coupling a semiconductor with strong spinorbit interaction to a superconductor enables the creation of Majorana zero modes (MZMs), the fundamental building blocks of topological quantum bits (qubits). Using a twodimensional electron gas (2DEG) as the semiconducting material offers the possibility to create complex networks that are required for the proposed qubit schemes. Among the 2DEG candidates, InSb is particularly promising due to a large Landé gfactor, strong spinorbit interaction and a high mobility. Studying the normal state properties of these InSb 2DEGs, we find peak mobilities of 180,000 cm^{2}/Vs, a spinorbit length of ̴200 nm, and phase coherent transport across long distances (> 10 um).
We couple these highquality 2DEGs to a superconductor (NbTiN) to create Josephson junctions (JJs) and thus provide the first demonstration of induced superconductivity in InSb 2DEGs. We find that the supercurrent in these JJs is gatetuneable and can be carried over distances of several microns. Measurements of multiple Andreev reflections and excess current indicate a large induced superconducting gap ( ̴1meV) along with reasonably high transparency (0.70.8). The application of a large magnetic field in the plane of the sample results first in a reduction and then in a reentrance of the supercurrent, compatible with a Zeemaninduced 0π transition in the JJs.
These results are an important step forward in using InSb 2DEGs for Majorana physics, especially in light of recent proposals for the generation of phasecontrollable MZMs in planar JJs.

9:15 – 9:50 
Ramon Aguado 
Andreev bound states (ABSs) in hybrid semiconductorsuperconductor nanowires can have nearzero energy in parameter regions where band topology predicts trivial phases. This surprising fact has been used to challenge the interpretation of a number of transport experiments in terms of nontrivial topology with Majorana zero modes (MZMs). I will discuss how this ongoing ABS versus MZM controversy is fully clarified when framed in the language of nonHermitian topology, the natural description for open quantum systems. This change of paradigm allows us to understand topological transitions and the emergence of pairs of zero modes more broadly, in terms of exceptional point (EP) bifurcations of system eigenvalue pairs in the complex plane. Within this framework, I will argue that some zero energy ABSs are actually nontrivial, and share all the properties of conventional MZMs, such as the recently observed 2e^{2}/h conductance quantization. From this point of view, any distinction between such ABS zero modes and conventional MZMs becomes artificial. The key feature that underlies their common nontrivial properties is an asymmetric coupling of Majorana components to the reservoir, which triggers the EP bifurcation. 
09:50 – 10:25 
Floris Zwanenburg 
Ge/Si core/shell nanowires are proposed candidates for observing Majorana fermions where a hard superconducting gap is essential for topological protection at zero energy. In double quantum dots, we observe shell filling of new orbitals and corresponding Pauli spin blockade. In nanowires with superconducting Al leads we create a Josephson junction via proximityinduced superconductivity. A gatetuneable supercurrent is observed with a maximum of ~60 nA. We identify two different regimes: Cooper pair tunnelling via multiple subbands in the open regime, while near depletion a supercurrent is carried by singleparticle levels of a quantum dot operating in the fewhole regime. Secondly, we create ambipolar quantum dots in silicon nanoMOSFETs. In recent devices, we have investigated the conformity of aluminium, titanium and palladium nanoscale gates by means of transmission electron microscopy (TEM). Subsequently, we have defined lowdisorder quantum dots with Pd gates. Finally, we have made depletionmode hole quantum dots in undoped silicon. We use fixed charge in a SiO_{2}/Al_{2}O_{3} dielectric stack to induce a 2DHG at the Si/SiO_{2} interface. This depletionmode design avoids complex multilayer architectures requiring precision alignment and allows directly adopting best practices already developed for depletion dots in other material systems. 
10:25 – 11:15 
COFFEE BREAK 
Please set up your posters during this coffee break and latest before the afternoon coffee break 
11:15 – 11:50 
Charles Marcus 

11:50 – 12:25 
Seigo Tarucha 
Proximityinduced superconductivity is a core concept of expressing exotic superconducting properties. Furthermore, when combined with Cooper pair splitting (CPS), generalized Majorana fermion is predicted to emerge. Here we study the CPS proximityinduced superconductivity using an Al/InAs double nanowire/Al junction having two top gates. The normal conductance shows plateaus of quantized values as functions of two gate voltages, reflecting the conductance quantization of the respective nanowires. Measurement of supercurrent at various bias points of conductance plateaus reveals the switching current due to CPS to the two nanowires significantly larger than that due to local pair tunneling to the respective nanowires, indicating dominant contributions from the CPS superconductivity. Additionally, from the dependence on the number of nanowire channels, the observed CPS is assigned to electronelectron interactions or TomonagaLuttinger liquid effects, not electrostatic energy. These results may expand the flexibility in engineering proximityinduced superconductivity and help to realize Majorana Fermions and parafermions without magnetic fields.

12:25 – 13:00 
Jelena Klinovaja 
Semiconducting quantum wires defined within twodimensional electron gases and strongly coupled to thin superconducting layers have been extensively explored in recent experiments as promising platforms to host Majorana bound states. We study numerically such a geometry, consisting of a quasionedimensional wire coupled to a disordered threedimensional superconducting layer [15]. In the strongcoupling limit of a sizable proximityinduced superconducting gap, all transverse subbands of the wire are significantly shifted in energy relative to the chemical potential of the wire. For the lowest subband, this band shift is comparable in magnitude to the spacing between quantized levels that arise due to the finite thickness of the superconductor (which typically is ~500 meV for a 10nm thick layer of Aluminum); in higher subbands, the band shift is much larger. Additionally, the width of the system, which is usually much larger than the thickness, and moderate disorder within the superconductor have almost no impact on the induced gap or band shift. We provided a detailed discussion of the ramifications of our results, arguing that a huge band shift and significant renormalization of semiconducting material parameters in the strongcoupling limit make it challenging to realize a topological phase in such a setup, as the strong coupling to the superconductor essentially metallizes the semiconductor. This metallization of the semiconductor can be tested experimentally through the measurement of the band shift. References: 
13:00 – 15:00 
LUNCH 
Lunch at Costa Vasca at 13:15. 
15:00 – 15:35 
Takis Kontos 

15:35 – 16:10 
Felix von Oppen 
In this talk, I present a unified framework for Majoranabased faulttolerant quantum computation with Majorana surface codes. All logical Clifford gates are implemented with zerotime overhead. This is done by introducing a protocol for Pauli product measurements with tetrons and hexons which only requires local fourMajorana parity measurements. An analogous protocol is used in the faulttolerant setting, where tetrons and hexons are replaced by Majorana surface code patches, and parity measurements are replaced by lattice surgery, still only requiring local fewMajorana parity measurements. To this end, we discuss twist defects in Majorana fermion surface codes and adapt the technique of twistbased lattice surgery to fermionic codes. Majorana surface codes can be used to decrease the space overhead and stabilizer weight compared to their bosonic counterparts.

16:10 – 16:45 
Elsa Prada 
Numerous signatures of possible Majorana zero modes in nanowire devices have now been observed in different labs in the form of zerobias transport anomalies. Their interpretation, however, remains under debate. The core of the issue lies in determining whether the anomalies are associated to zero modes with a high degree of nonlocality, characteristic of Majorana zero modes of topological origin. Determining the degree of wave function overlap is a hard experimental problem. Here we discuss the physically relevant measure of nonlocality, and show how it can be faithfully estimated using a local measurement on one end of the nanowire. The precision of the estimator is quantified for homogeneous and inhomogeneous nanowires, with sharp and smooth potential and pairing profiles. The latter has been argued to host socalled trivial zero modes. We show that even for these states the estimator is useful, and provides bounds to their degree of nonlocality.

16:45 – 17:15 
COFFEE BREAK 

17:15 – 17:50 
Andrea Donarini 
Illumination of three level atoms (λsystems) by detuned lasers can pump electrons into a coherent superposition of hyperfinesplit levels which can no longer absorb light. Because fluorescent light emission is then suppressed, the coherent superposition is known as a dark state.
We report an allelectric analogue of this destructive interference effect in a carbon nanotube quantum dot. A dark state is in this case a coherent superposition of states with opposite angular momentum which is fully decoupled from either the drain or the source leads. The emergence of dark states impacts the currentvoltage characteristics, where missing current steps are observed depending on the sign of the applied sourcedrain bias. Our results demonstrate for the first time coherentpopulation trapping by allelectric means in an artificial atom.
The existence of the dark states relies on the (quasi) valley degeneracy of the CNT and on the particular coupling to the metallic leads. The difference between the tunneling phases to the two electrodes is the most relevant parameter of the theory. Besides
characterizing the dark states, this phase difference determines also the precession dynamics of the pseudospin associated to the orbital degeneracy. This theory predicts current suppression with a specific gate and bias dependence which accurately matches the experimental results.

17:50 – 18:25 
Dominik Zumbühl 
Spins in semiconductors offer themselves for spintronics and are leading candidates for quantum computing. The spin relaxation time T_{1} sets a fundamental upper bound for the coherence time and e.g. the spin readout fidelity. More than 15 years ago, it was predicted that at low magnetic fields, the dominant mechanism is the coupling to the nuclear spins, where the relaxation becomes isotropic and the scaling changes to T_{1} ∝ B^{3}. We establish these predictions in a GaAs quantum dot [1], by measuring T_{1} over a large range of fields – made possible by lower temperature and control of the field direction – and report a T_{1} = 57 ± 15 s, setting a record for the spin lifetime in a nanostructure. It is tempting and elegant to think of the spin alone as the carrier of quantum information. However, the spin is hosted by an electron with charge and quantum orbitals. The spinorbit and hyperfine interactions depend on these orbitals, and this can be exploited to control spin relaxation and electricdipole spin resonance for coherent manipulation. We present a noninvasive technique [2] which delivers the orientation angle of the orbitals in the plane as well the zconfinement, based on a model of flux threading of a 3D dot [3] and measurements of the xyorbital spectrum in an inplane magnetic field of varying magnitude and direction. From the extracted zconfimenent and zelectric field, we can calculate the Rashba and Dresselhaus spinorbit strengths. This gives good agreement with values from the T_{1} anisotropy as well as independent experiments [4], where we demonstrated how the persistent spin helix can be stretched with top and back gate voltages. Further, the spin helix symmetry can be exploited to derive a closedform expression for the weak localization magnetoconductivity [5] – the paradigmatic signature of spinorbit coupling. We present a reliable method to extract all parameters from fits to the new expression, obtaining very good agreement with other experiments. This provides experimental confirmation of the new theory, and advances spinorbit coupling as powerful resource in emerging quantum technologies. References: 
9:15 – 9:50 
Georgios Katsaros 
The interest in holes as potential spin qubits has strongly increased in the past few years. Due to the intrinsically large spin orbit coupling, hole spin qubits should be electrically tunable and show high Rabi frequencies. Indeed in 2016, the first hole spin qubit with Rabi frequencies as high as 70MHz was demonstrated [1]. Here we present the first Ge hole spin qubit. The qubit is formed in a Ge hutwire [2] double quantum dot. Presumably due to the even stronger spin orbit coupling in Ge, Rabifrequencies of 140 MHz were reached [3]. Ramsey experiments revealed dephasing times exceeding 130 ns. Finally, by measuring the spin relaxation time of holes in Ge hut wires an upper bound for the coherence time could be extracted [4]. References: 
09:50 – 10:25 
Jason Petta 
Electron spins are excellent candidates for solid state quantum computing due to their exceptionally long quantum coherence times, which is a result of weak coupling to environmental degrees of freedom. However, this isolation comes with a cost, as it is difficult to coherently couple two spins in the solid state, especially when they are separated by a large distance. Here we combine a large electricdipole interaction with spinorbit coupling to achieve spinphoton coupling [1]. Vacuum Rabi splitting is observed in the cavity transmission as the Zeeman splitting of a single spin is tuned into resonance with the cavity photon. We achieve a spinphoton coupling rate as large as g_{s}/2π = 10 MHz, which exceeds both the cavity decay rate κ/2π = 1.8 MHz and spin dephasing rate γ/2π = 2.4 MHz, firmly anchoring our system in the strongcoupling regime [2]. Moreover, the spinphoton coupling mechanism can be turned off by localizing the spin in one side of the double quantum dot. These developments in quantum dot cQED, combined with recent demonstrations of highfidelity twoqubit gates in Si, firmly anchor Si as a leading material system in the worldwide race to develop a scalable quantum computer [3]. References: 
10:25 – 11:15 
COFFEE BREAK 

11:15 – 11:50 
Silvano De Franceschi 
Silicon and its close relative germanium form the core materials of the wellestablished microelectronics industry. Lately, they have enabled remarkable progress also in the raising field of quantum technologies, generating at the same time new fundamental questions and technological challenges. In fact, there is still a lot to know about these wellknown semiconducting materials and their potential for quantum applications. In this talk, I will focus on holebased systems made from silicon and silicongermanium nanostructures. I will present recent experiments dealing with spinrelated effects, and discuss their implications for holespin qubits and, more generically, quantum spintronic devices.

11:50 – 12:25 
Leo Kouwenhoven 
Majoranas in semiconductor nanowires can be probed via various electrical measurements. Tunnel spectroscopy have revealed zerobias peaks in the differential conductance. When the existence of Majoranas is firmly established, the next challenge is to build Majorana qubits. We discuss the different qubit schemes and report on our first building blocks. The promise of Majorana qubits is that the error rate is very low yielding a relatively simple scalable architecture.
Recent papers: 
12:25 – 13:00 
Christian Schönenberger 
In this talk I will present recent results in the field of “quantum designer physics” using 2D van der Waals (vdW) heterostructures. The first result relates to proximityinduced spinorbit interaction (SOI) in stacks of WSe2graphene. The second to the role of edge relative to bulk current in graphenehBN superlattices. Large spinorbital proximity effects have been predicted in graphene interfaced with a transitionmetal dichalcogenide layer. Whereas clear evidence for an enhanced spinorbit coupling has been found at large carrier densities, the type of SOI and its relaxation mechanism remained unknown. We have found an increased SOI close to the charge neutrality point (DP) in graphene, where topological states are expected to appear. Dopingdependent measurements have shown that the spin relaxation of the inplane spins is largely dominated by a valleyZeeman term and that the intrinsic spinorbit coupling plays a minor role in spin relaxation. In graphene devices, several reports have pointed to an unequal current distribution, which can be deduced from the socalled Fraunhofer pattern in graphenebased Josephson junctions. In particular, a large edgecurrent contribution appeared in some cases close to the DP, leading to the suggestion that a gap might open. We have recently looked into the current distribution using the same approach in devices that show a superlattice structure due to lattice mismatch between graphene and hBN. We also found an excess edge current not at the DP, but rather at the points where van Hove singularities (vHS) form. We argue that the effective transport time in the bulk increases at the vHSs, due to the suppression of the Fermi velocity, while the current continues to flow along the edges. At the moment the two experiments discussed before are not directly connected. However, we aim to study Josephson junctions with proximityinduced spinorbit interaction next. Acknowledgment: This work has been done by the following list of contributors in alphabetic order: A. W. Cummings, R. Delagrange, J. H. Garcia, D. I. Indolese, M. Kedves, P. Makk, T. Taniguchi, J. Wallbanks, K. Watanabe, S . Zihlmann. I am very grateful to them! The work has financially been supported by the Swiss NSF, graphene flagship, ERC, SNFQSIT, SNI and further organizations. 
13:00 – 15:00 
LUNCH 
Lunch at Costa Vasca at 13:15. 
15:00 – 15:35 
Philip Kim 
A pair of electron and hole across the interface of semiconductor heterostructure can form a bound quantum state of the interlayer exciton. In a coupled interface between atomically thin van der Waals layers, the Coulomb interaction of the interlayer exciton increases further. Coulomb drag effect is a mesoscopic effect which manifests manybody interactions between two lowdimensional systems, which has served an extremely useful probe the strong correlation in quantum systems. In this presentation, we will first discuss observing interlayer exciton formation in semiconducting transition metal dichalcogenide (TMDC) layers. Unlike conventional semiconductor heterostructures, charge transport in of the devices is found to critically depend on the interlayer charge transport, electronhole recombination process mediated by tunneling across the interface. We demonstrate the enhanced electronic, optoelectronic performances in the vdW heterostructures, tuned by applying gate voltages, suggesting that these a few atom thick interfaces may provide a fundamental platform to realize novel physical phenomena. In addition, spatially confined quantum structures in TMDC can offer unique valleyspin features, holding the promises for novel mesoscopic systems, such as valleyspin qubits. In the second part of the presentation, we will discuss magnetoexciton condensation. In this electronic double layer subject to strong magnetic fields, filled Landau states in one layer bind with empty states of the other layer to form an exciton condensate. Driving current in one graphene layer generates a nearquantized Hall voltage in the other layer, resulting in coherent exciton transport. In our experiment, capitalizing strong Coulomb interaction across the atomically thin hBN separation layer, we realize a superfluid condensation of magneticfieldinduced excitons. For small magnetic fields (the BEC limit), the counterflow resistance shows an activation behavior. On the contrary, for large magnetic fields limit where the interexciton separation decreases (the BCS limit), the counterflow resistance exhibits sharp transitions in temperature showing characters of BerezinskiiKosterlitzThouless (BKT) transition. Furthermore, complete experimental control of density, displacement and magnetic fields in our graphene double layer system enables us to explore the rich phase diagram of several superfluid exciton phases with the different internal quantum degrees of freedom.

15:35 – 16:10 
Sergio Valenzuela 
Graphene and other twodimensional materials have rapidly established themselves as promising building blocks for spintronic applications. Due to weak spinorbit coupling and a lack of hyperfine interaction with the predominant zerospin isotope 12C, the spin lifetime in graphene was expected to be in the microsecond or even millisecond range. However, in contrast to these expectations, experiments have demonstrated spin lifetimes typically below 10 ns. In the first part of the talk, I will introduce the two main theoretical models that are currently being considered to explain such a fast spin relaxation. They are unique to graphene and involve either resonant scattering with magnetic centers or spinpseudospin coupling and Rashba spinorbit interaction [1]. I will then discuss recent experimental efforts aiming at highlighting their peculiarities; in particular, at verifying whether the spin relaxation is anisotropic, which would be the hallmark of the presence of a dominant spin orbit field [1,2]. These experimental efforts can also provide valuable information of spinorbit proximity effects and spin Hall effects, allowing us to demonstrate highly anisotropic spin relaxation in graphene/transitionmetal dichalcogenide heterostructures [3,4] and large spintocharge conversion in graphene/Pt devices [5]. In the second part of the talk, I will discuss the generation, propagation and detection of hot carriers in graphene using purely electrical means. I will show that because typical carrier cooling times can be similar to spin lifetimes, it is possible to implement nonlocal hotcarrier injection and detection methods analogous to those used for spin [6]. In addition, I will present evidence that the spin propagation can be reinforced (suppressed) by the presence of hot carriers [7]. References: 
16:10 – 16:45 
Mikhail Otrokov 
This talk reports on recent studies aimed at the implementation of robust magnetism and/or strong spinorbit coupling (SOC) to graphene grown on metallic substrates. In the first part, we will discuss the observation of quasifreestanding graphene with strong exchange and SO splittings achieved simultaneously (a socalled magnetospinorbit graphene). In Ref. [1], using spin and angleresolved photoemission spectroscopy (ARPES) it has been found that the Dirac state in the Auintercalated graphene on Co(0001) experiences a giant spin splitting, while being by no means distorted due to interaction with the substrate. Scanning tunneling microscopy (STM) data suggest that the peculiar reconstruction of the Au/Co(0001) interface is responsible for the exchange field transfer to graphene. Calculations based on density functional theory (DFT) reveal the splitting to stem from the combined action of the Co thin film induced inplane exchange field and Auinduced Rashba SOC. The second part of the talk is devoted to a combined STM, (spin)ARPES and DFT study of graphene/Pb/Ir(111), Ref [2]. Pb intercalation between graphene and Ir(111) reduces the coupling to the substrate in such a way that its corrugation becomes negligible and distortions of the linear dispersion largely disappear, as compared to graphene/Ir(111), while graphene's sublattice symmetry is maintained. Remarkably, the spinorbit splittings induced by the proximity of the Ir(111) surface are preserved after Pb intercalation in a wide energy range. It is further shown that the Pb/Ir(111) surface induces a complex spin texture in graphene bands with both inplane and outofplane components, that are fingerprints of the Rashba and KaneMele couplings, respectively. References: 
16:45 – 19:00 
POSTER SESSION 
Bestposter prizes are sponsored by Nature Reviews Physics and DIPC 
9:15 – 9:50 
Fernando De Juan 
In crystalline materials that break inversion symmetry, light pulses can generate DC currents via photogalvanic effects. In this talk I will describe a surprising topological aspect of this effect that occurs when the light is circularly polarized: in chiral nodal semimetals, the magnitude of the current is exactly quantized in terms of fundamental constants only. This occurs because this response function measures the monopole Berry flux of the node, a rare example of quantization in a gapless system at finite frequency. I will discuss how to measure the effect both in chiral Weyl semimetals, as well as in more complex chiral multifold band crossings that have been recently predicted. I will also show how this quantized response can be distinguished from other circular intraband currents that are unavoidable in metallic systems.

09:50 – 10:25 
Claudia Felser 
Topology a mathematical concept became recently a hot topic in condensed matter physics and materials science. One important criteria for the identification of the topological material is in the language of chemistry the inert pair effect of the selectrons in heavy elements and the symmetry of the crystal structure [1]. Beside of Weyl and Dirac new fermions can be identified compounds via linear and quadratic 3, 6 and 8 band crossings stabilized by space group symmetries [2]. Binary phoshides are the ideal material class for a systematic study of Dirac and Weyl physics. Weyl points, a new class of topological phases was also predicted in NbP, NbAs. TaP, MoP and WP2. [37]. In magnetic materials the Berry curvature and the classical AHE helps to identify interesting candidates. Magnetic Heusler compounds were already identified as Weyl semimetals such as Co2YZ [810], in Mn3Sn [11,12] and Co3Sn2S2 [13]. The Anomalous Hall angle helps to identify even materials in which a QAHE should be possible in thin films. Besides this kspace Berry curvature, Heusler compounds with noncollinear magnetic structures also possess realspace topological states in the form of magnetic antiskyrmions, which have not yet been observed in other materials [14]. References: 
10:25 – 11:15 
COFFEE BREAK 

11:15 – 11:50 
María Vozmediano 
We show that a conformal anomaly in Weyl/Dirac semimetals generates a bulk electric current
perpendicular to a temperature gradient and the direction of a background magnetic field. The
associated conductivity of this novel contribution to the Nernst effect is fixed by a beta function
associated with the electric charge renormalization in the material.

11:50 – 12:25 
Stuart Parkin 

12:25 – 13:00 
Jairo Sinova 
Antiferromagnetic spintronics considers the active manipulation of the antiferromagnetic order parameter in spinbased devices. An additional concept that has emerged is that antiferromagnets provide a unifying platform for realizing synergies among three prominent fields of contemporary condensed matter physics: Dirac quasiparticles and topological phases. Here spintronic devices made of antiferromagnets with their unique symmetries will allow us to control the emergence and to study the properties of Dirac/Weyl fermion topological phases that are otherwise principally immune against external stimuli. In return, the resulting topological magnetotransport phenomena open the prospect of new, highly efficient means for operating the antiferromagnetic memorylogic devices. We discuss how these topological phases emerge and how their robustness depends on the relative orientation of the Neel order parameter that can be manipulated by Neel spinorbit torques. Their natural excitations are in the THz but with the additional consideration that they can now be directly tuned.

13:00 – 13:10 
Giulia Pacchioni 
Announcement of the winners of the poster session competition, sponsored by Nature Reviews Physics and DIPC 
13:10 – 15:00 
LUNCH 
Lunch at Costa Vasca at 13:25. 
15:00 – 15:35 
Ali Yazdani 

15:35 – 16:10 
Roland Wiesendanger 
Majorana states in atomicscale magnetsuperconductor hybrid systems have recently become of great interest because they can encode topological qubits and ultimately provide a new direction in topological quantum computation [1,2]. First, we will focus on artificially fabricated 1D atomic chains of magnetic Fe adatoms on a high spinorbit coupled superconducting Re(0001) substrate using STMbased atommanipulation techniques at T=350 mK. Spinpolarized STM measurements [3] reveal the presence of noncollinear spin textures, i.e. spin spiral ground states, stabilized by interfacial DzyaloshinskiiMoriya interactions [4] as found earlier for selfassembled biatomic Fe chains on Ir(001) [5]. Tunneling spectra measured spatially resolved on the Featom chain on Re(0001) reveal the evolution of the spatially and energetically resolved local density of states as well as the emergence of zeroenergy bound states at the chain ends above a critical chain length. Based on the exact knowledge of the geometrical, electronic, and spin structure of the magnetic chain – superconductor hybrid system, the experimental results can be compared rigorously with abinitio and modeltype tightbinding calculations supporting the interpretation of the spectroscopic signatures at the ends of the chains as Majorana bound states [6]. In the second part, the atomicscale design of more complex network structures for Majorana state manipulation, including braiding operations will be discussed. Moreover, we will also address recent experimental and theoretical studies of monolayer topological superconductivity and chiral Majorana edge modes in modeltype 2D magnetic islands on elemental superconductors [7]. Finally, the prospects for studies of Majorana states in skyrmion – superconductor hybrid systems [8] will be highlighted. References: 
16:10 – 16:45 
Pascal Simon 
In recent years, a renewed interest in magnetic impurities in superconductors was driven by their potential as a new platform for topological superconductivity. Recent scanning tunneling spectroscopy measurements on a superconducting monolayer of lead (Pb) with nanoscale cobalt islands, have revealed puzzling quasiparticle ingap states [1] which demand a better understanding of twodimensional superconductivity in presence of spinorbit coupling and magnetism. Tantalizingly, the quasiparticle states evoke general topologically protected states which haven't yet been explored in twodimensional superconductors. Thus motivated, we theoretically study a model of twodimensional swave superconductor with a fixed configuration of exchange field and spinorbit coupling terms allowed by symmetry. Using analytics and exact diagonalization of tightbinding models, we find that a vortexlike defect in the Rashba spinorbit coupling binds a single Majorana zeroenergy (midgap) state. Importantly, in contrast to the case of a superconducting vortex [2], our spinorbit defect does not create a tower of ingap excitation states. Our findings match the puzzling features observed in the experiment, particularly: (1) preservation of superconducting gap, and (2) short localization length of the zeroenergy state compared to the superconductor coherence length [3]. Additionally, these properties indicate that the system realizes the coveted wellprotected Majorana states, which is a key requirement for a potential realization of a topological qubit. We also discuss how the quasiparticle states of the defect relate to the states of superconductors on top of magnetic textures, such as skyrmions. References: 
16:45 – 17:15 
COFFEE BREAK 

17:15 – 17:50 
Patrick Lee 
1TTaS_{2} is a charge density wave layered TMD material that was thoroughly studied in the early 1970's. It is unique among the 2D CDW materials in that it has an insulating ground state. It was understood as an example of a cluster Mott insulator: the lattice distortions create 13 Ta site "star of David" clusters which form a triangular lattice with one electron per cluster. Mott insulators are expected to from local moments which eventually order magnetically, but no sign of the local moment or magnetism has ever been found. We proposed that the local moments may have formed a quantum spin liquid, an exotic and elusive state proposed by Anderson in 1973. Recently this proposal received strong support by the observation of a linear T term in the thermal conductivity by Matsuda's group (arXiv 1803.06100), which we interpret as being due to a spinon Fermi surface in a charge insulator. We support this interpretation with DMRG calculations, showing peaks at 2k_{F} in the spin structure factor. We discuss the prospects of finding high temperature superconductor by doping monolayer samples by gating.

17:50 – 18:25 
Miguel Angel Cazalilla 
In this talk, I will describe two kinds of magnetic phenomena on
the edge of topological systems. In the first part of the talk, I
consider the properties of a localized magnetic impurity that is strongly
coupled to a quantum spin Hall (QSHI) edge. It will be shown that the
impurity can lead to antiresonances in the transmission coefficient, which
can have a dramatic effect on the transport properties of the edge channel.
When the electrons at the Fermi energy of the edge channel are on resonance,
interaction effects lead to a temperature dependent broadening of the antiresonance
for both repulsive and moderately attractive interactions in the channel.
Consequences for QSHI in proximity to a superconductor (a system
that is relevant for the search of Majorana bound states) will be also
discussed , time permitting.
In the second part of the talk, the spin excitations localized at the edge
of a finite chain of halfinteger spin magnetic adatoms are characterized
using the timedependent density matrix renormalization algorithm. It
is argued that the understanding of such excitations allows to construct
an effective lowenergy model that can account for the spatial location of
the Kondo resonances observed in recent experiments.

20:30 – 23:00 
CONFERENCE DINNER 
Restaurante Ni Neu (Address: Zurríola Hiribidea, 1, DonostiaSan Sebastián) See howtogetthere instructions and map 