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Ilya Sochnikov

Publications and source records attributed to Ilya Sochnikov.

24 records · Page 2Linked to original sources

Isolation solution for extreme environmental vibrations for quantum-enabling cryogenic setups installed on raised frames

Cryogenic quantum sensing techniques are developing alongside the ever-increasing requirements for noiseless experimental environments. For instance, several groups have isolated internal system vibrations from cold heads in closed-cycle dilution refrigerators. However, these solutions often do not account for external vibrations, necessitating novel strategies to isolate the entire cryogenic systems from their environments in a particular set of raised cryostats. Here, we introduce a dual-stage external active vibration-isolation solution in conjunction with a closed-cycle dilution refrigerator that isolates it from the environment. This dual stage includes two sets of active attenuators and a customized steel tower for supporting experimental probes at heights of 3 m from the floor. Both stages achieve 20-40 dB of attenuation with the active systems engaged, corresponding to levels of vibration in the VC-G range (a standardized Vibration Criterion appropriate for extremely quiet research spaces) on the cryostat's room temperature baseplate and the steel tower. Our unique vibration isolation solution therefore expands the applications of modern cryogenic equipment beyond exclusively quiet specialty buildings, rendering such equipment suitable for interdisciplinary, open-floor research centers.

physics.ins-det↗

A local maximum in the superconducting transition temperature of Nb-doped strontium titanate under uniaxial compressive stress

Superconducting strontium titanate (STO) is in the spotlight as a low carrier concentration semiconductor in proximity to polar order. Its superconducting pairing mechanism poses an open fundamental challenge, which may be resolved by controlling how strongly the superconducting and polar orders interact. Here, we show for the first time that non-monotonic superconducting transition temperature behavior in uniaxially compressed STO can occur, revealing a reduction followed by a peak in the superconducting transition temperature. The corresponding displacements in the lattice are extremely small, in the sub picometer range, indicating that this material approaches a singularity in electron-phonon coupling, consistent with STO transforming to the polar (ferroelectric) phase that influences the superconductivity.

cond-mat.supr-con↗

Precision measurements of the AC field dependence of the superconducting transition in strontium titanate

Strontium titanate has resurfaced as a material prompting vigorous debate about the origin of its superconductivity in the extremely low carrier concentration regime. Here, we used simultaneous AC susceptibility and transport methods to explore the superconducting phase transition region in this material. We determined that strontium titanate is extremely sensitive to even small AC fields, which also influence the resistive transition; we suggest that extreme vortex sizes and mobilities contribute to this large effect. Our findings will be of importance for accurately determining transition temperature, informing the debate about the pairing mechanism in strontium titanate, for which even millikelvin errors may be critical.

cond-mat.supr-con↗

Real-space imaging and flux noise spectroscopy of magnetic dynamics in Ho$_2$Ti$_2$O$_7$

Holmium titanate (Ho$_2$Ti$_2$O$_7$) is a rare earth pyrochlore and a canonical example of a classical spin ice material. Despite the success of magnetic monopole models, a full understanding of the energetics and relaxation rates in this material has remained elusive, while recent studies have shown that defects play a central role in the magnetic dynamics. We used a scanning superconducting quantum interference device (SQUID) microscope to study the spatial and temporal magnetic fluctuations in three regions with different defect densities from a Ho$_2$Ti$_2$O$_7$ single crystal as a function of temperature. We found that the magnetic flux noise power spectra are not determined by simple thermally-activated behavior and observed evidence of magnetic screening that is qualitatively consistent with Debye-like screening due to a dilute gas of low-mobility magnetic monopoles. This work establishes magnetic flux spectroscopy as a powerful tool for studying materials with complex magnetic dynamics, including frustrated correlated spin systems.

cond-mat.str-el↗

Strain-engineered interaction of quantum polar and superconducting phases

Much of the focus of modern condensed matter physics concerns control of quantum phases with examples that include flat band superconductivity in graphene bilayers, the interplay of magnetism and ferroelectricity, and induction of topological transitions by strain. Here we report the first observation of a reproducible and strong enhancement of the superconducting critical temperature, $T_c$, in strontium titanate (SrTiO3) obtained through careful strain engineering of interacting superconducting phase and the polar quantum phase (quantum paraelectric). Our results show a nearly 50% increase in $T_c$ with indications that the increase could become several hundred percent. We have thus discovered a means to control the interaction of two quantum phases through application of strain, which may be important for quantum information science. Further, our work elucidates the enigmatic pseudogap-like and preformed electron pairs phenomena in low dimensional strontium titanate as potentially resulting from the local strain of jammed tetragonal domains.

cond-mat.supr-con↗

Non-sinusoidal current-phase relationship in Josephson junctions from the 3D topological insulator HgTe

We use Superconducting QUantum Interference Device (SQUID) microscopy to characterize the current-phase relation (CPR) of Josephson Junctions from 3-dimentional topological insulator HgTe (3D-HgTe). We find clear skewness in the CPRs of HgTe junctions ranging in length from 200 nm to 600 nm. The skewness indicates that the Josephson current is predominantly carried by Andreev bound states with high transmittance, and the fact that the skewness persists in junctions that are longer than the mean free path suggests that the effect may be related to the helical nature of the Andreev bound states in the surface of HgTe.

cond-mat.mes-hall↗