High-temperature Josephson diode Sanat Ghosh1 Vilas Patil1 Amit Basu1 Kuldeep1 Achintya Dutta1 Digambar A. Jangade1 Ruta Kulkarni1 A. Thamizhavel1 Jacob F. Steiner2 Felix von

2025-05-06 0 0 3.8MB 46 页 10玖币

侵权投诉

High-temperature Josephson diode

Sanat Ghosh∗1, Vilas Patil1, Amit Basu1, Kuldeep1, Achintya Dutta1, Digambar

A. Jangade1, Ruta Kulkarni1, A. Thamizhavel1, Jacob F. Steiner2, Felix von

Oppen2, and Mandar M. Deshmukh†1

1Department of Condensed Matter Physics and Materials Science, Tata Institute

of Fundamental Research, Homi Bhabha Road, Mumbai 400005, India

2Dahlem Center for Complex Quantum Systems and Fachbereich Physik, Freie

Universität Berlin, 14195 Berlin, Germany

Abstract

Symmetry plays a critical role in determining various properties of a material. Semiconducting

p-n junction diodes exemplify the engineered skew electronic response and are at the heart

of contemporary electronic circuits. The non-reciprocal charge transport in a diode arises

from doping-induced breaking of inversion symmetry. Breaking of time-reversal, in addition

to inversion symmetry in some superconducting systems, leads to an analogous device – the

superconducting diode. Following the pioneering ﬁrst demonstration of the superconducting

diode eﬀect (SDE) [1], a plethora of new systems showing similar eﬀects have been reported

[2,3,4,5,6,7,8,9,10]. SDE lays the foundation for realizing ultra-low dissipative circuits,

while Josephson phenomena-based diode eﬀect (JDE) can enable realization of protected qubits

[11,12]. However, SDE and JDE reported thus far are at low temperatures (∼4K or lower)

and impede their adaptation to technological applications. Here we demonstrate a Josephson

diode working up to 77 K using an artiﬁcial Josephson junction (AJJ) of twisted layers of

Bi2Sr2CaCu2O8+δ(BSCCO). The non-reciprocal response manifests as an asymmetry in the

magnitude of switching currents as well as their distributions, and appears for all twist angles.

The asymmetry is induced by and tunable with a very small magnetic ﬁeld applied perpendic-

ular to the junction. We report a record asymmetry of 60 % at 20 K. We explain our results

within a vortex-based scenario. Our results provide a path toward realizing superconducting

quantum circuits at liquid nitrogen temperature.

∗sanatghosh1996@gmail.com

†deshmukh@tifr.res.in

arXiv:2210.11256v2 [cond-mat.supr-con] 16 Apr 2023

Introduction

Breaking of inversion and time-reversal symmetry is typically required to realize SDE [13].

Several proposals for realizing the superconducting analogue of the diode eﬀect [14,15,16]

have been explored. It was followed by successful demonstrations in various systems such as

non-centrosymmetric superconductors [1,2,3], two-dimensional electron gases [4], patterned

superconductors [5,6], superconductor/ferromagnet multilayers [7,8], and twisted graphene

systems [9,17]. Although several diﬀerent mechanisms [3,18,19,20,21,22] have been pro-

posed to describe the observations across systems, the theories are still at their early stage of

development. The SDE/JDE, which is the result of non-reciprocal response in these systems,

manifests in terms of diﬀerent magnitudes of superconducting switching currents (I+

s6=I−

in the two opposite polarities. The eﬀect has been demonstrated as magnetic ﬁeld induced

[1,5,6,3,2,4] and ﬁeld free [7,8,9] in nature. In terms of practical usability, however, all re-

ports to date require very low temperatures, 4 K or less, to operate. We overcome this challenge

using c-axis Josephson junctions (JJ) between ﬂakes of a high-Tccuprate superconductor.

We demonstrate JDE in an artiﬁcially created Josephson junction (AJJ) by twisting two

layers of BSCCO [23] that can be exfoliated to atomically ﬂat ﬂakes [24,25,26,27] sustaining

superconductivity down to the monolayer limit [28]. The diﬀerence between the magnitude of

positive (I+

s) and negative (I−

s) switching currents and their statistical distributions, in these

junctions, are tunable with a very small magnetic ﬁeld applied perpendicular to the plane of the

junction. The asymmetry persists from low temperature up to the superconducting transition

temperature (Tc,∼77 K) of the junction and increases as temperature decreases, reaching a

value as high as 60 % at 20 K. The diode behavior is demonstrated in terms of the half-wave

rectiﬁcation of a square wave current.

Heterostructures, assembled by twisting two layers of van der Waals materials oﬀer a new

platform for emergent electronic responses, entirely diﬀerent from the constituent materials. In

a similar spirit, a recent study [29] proposes the possibility of realizing time reversal symme-

try broken high-temperature topological superconductivity at the interface of two 45°twisted

BSCCO layers. Thus twisted BSCCO JJs oﬀer a natural platform to explore the physics of

JDE. Notably, our work demonstrates that JDE is a feature of the artiﬁcial c-axis JJs and does

not require a special angle, 45°, as long as inversion symmetry is broken.

Fabricating twisted BSCCO junctions, however, is extremely challenging, and many of the

junction properties are sensitive to fabrication methods. In the past, there have been numerous

studies on artiﬁcially created twisted junctions of BSCCO to study the pairing symmetry of

the superconducting order parameter. But the fabrication process involved high-temperature

oxygen annealing to sustain the superconductivity at the interface. This led to observations of

no [30,31,32] or diﬀerent [33,34] angular dependence of the Josephson coupling, diﬀerent than

the anticipated d-wave superconductivity in BSCCO [35,36]. Recently, there has been progress

in making twisted BSCCO JJs using room temperature exfoliation [32,34] and employing

cryogenic exfoliation [37].

We fabricate twisted BSCCO JJs following Zhao et al. [37]. The junctions are created by

re-exfoliating a relatively thicker BSCCO ﬂake into two pieces and stacking them, which ensures

alignment of the crystal axis and a well-deﬁned twist angle (with an accuracy of ±0.5°). The

re-exfoliation is done inside an Ar-ﬁlled glove box with a low-temperature stage. To avoid any

chemical contamination, Au contacts are directly deposited on the ﬂake through a pre-aligned

SiN mask. More details of the device fabrication are discussed in the methods section.

Experimental data

Fig. 1a and b show the schematic of the twisted BSCCO crystal structure and the device

geometry of the artiﬁcial JJ, respectively. The crystal structure of BSCCO is such that it has

its own IJJ. The superconducting Cu-O planes in this material, separated by the insulating

SrO/BiO buﬀer layers (green slabs in Fig. 1a), are Josephson coupled and constitute a series

of IJJs in the material structure [38]. By twisting two individual layers of BSCCO, we create

an AJJ at the interface, as indicated in Fig. 1a. The twist angle controls [34,37] the switching

current density (Js), and consequently the Josephson energy, of the AJJs (maximum for 0°,

and minimum for 45°twist) due to d-wave symmetry of the superconducting order parameter

in the system.

We made 10 AJJs with diﬀerent twist angles (four 45°, four 0°, and two 22°). In the main

text, we present data of one of 45°(D1) and 0°(D2) twisted junctions, and data of other twisted

junctions are shown in Supplementary Information Fig. S6 and Extended Data Fig. 4 (22°,

D5). The JDE is observed in all of the devices with diﬀerent twist angles, an important aspect

of our work. We design our devices such that we can simultaneously measure the junction

properties and the two ﬂakes that make the junction (Fig. 1b). We do this to ensure that there

is no degradation during the fabrication. First, we check the four terminal resistance across

the junction as a function of temperature which shows Tcsimilar to the pristine BSCCO ﬂake,

as shown in the Supplementary Information, Fig. S3. The pristine nature of the fabricated

junctions is evident from the fact that the 0°twisted junction has magnitude of switching current

density (Js) similar to the IJJs formed between the Cu-O planes in BSCCO (see Extended data

Fig. 1).

Fig. 1c shows dc I −Vacross the junction at 30 K and at ﬁxed B= 4.3µT, perpendicular to

the junction plane (see Fig. 1b). Temperature dependence of dc I−Vis shown in Supplementary

Information Fig. S11. We discuss the detailed ﬁeld dependence later. The two colored line plots

are for diﬀerent sweep directions of the bias current as indicated by the arrows. The bias current

is swept in the order as shown in the inset. We identify switching (Is) and retrapping currents

(Ir) in positive and negative bias range with I+

sand I−

s, as shown in Fig. 1c. The magnitude of

I+

sis diﬀerent from I−

s. The observed hysteresis between Isand Iris a well-understood physics

of an underdamped JJ [39].

To clearly see the diﬀerence between the two switching currents I+

sand I−

s, we plot the

I−Vcurves of the negative bias branch by ﬂipping their signs in Fig. 1d. From the plot, it is

IJJ

AJJ

BiO/SrO buffer layer

BSCCO1

BSCCO2

−100 −50 0 50 100

I (μA)

−4

−2

V (mV)

T = 30 K B = 4.3 μT

I+

I−

sI−

I+

t (s)

I (μA)

40 60 80 100 120

|I| (μA)

|V| (mV)

T = 30 K B = 4.3 μT

I+

|I−

r|I+

50 60 70 80 90 100 110 120 130

|Is| (μA)

100

200

300

counts

eB = 4.3 μT

T = 30 K

I+

|I−

Fig. 1: Asymmetry of switching currents in a 45°twisted artiﬁcial Josephson junction of

BSCCO. (a) Schematic of twisted BSCCO (not to scale). One unit cell of BSCCO is rotated at a

speciﬁc angle with respect to the other unit cell. In each unit cell, the Cu-O planes are separated by

insulating SrO/BiO buﬀer layers (green slabs) and constitute an intrinsic Josephson junction (IJJ). At

the interface of the twisted region, an artiﬁcial Josephson junction (AJJ) is formed. (b) Schematic of

the twisted BSCCO device with Au contacts for measurements. Electrodes 1 and 6 are used as source

and sink for the current, and properties across the twisted junction are measured with electrodes 3

and 4. Magnetic ﬁeld Bis perpendicular to the junction plane. (c) dc I−Vcharacteristic across the

junction at 30 K. The two diﬀerent colored line plots are for two diﬀerent sweep directions of the biasing

current, indicated by the arrows. Switching currents (Is) and retrapping currents (Ir) for positive and

negative bias regimes are marked with a superscript. The current through the device is swept in the

order as shown in the inset. (d) Absolute values of Iand Vfor both positive and negative bias range

for the same data in (c) at 30 K. The solid cyan and green curves are for switching branch. The dashed

cyan and green curves are for the retrapping branch. This plot clearly shows the asymmetry in the

magnitude of I+

sand I−

s. (e) Histograms of the switching currents, I+

sand I−

sat 30 K. 104switching

events were taken to get the distributions. The triggering voltage used for measuring switching currents

was ±0.2mV. The median values of these distributions also show asymmetry between the magnitude

of I+

sand I−

clear that I+

sis larger than |I−

s|. This means that at bias currents I,|I−

s|< I < I+

s, the system

will dissipate energy and act like a resistive element in negative bias and be superconducting

in positive bias. To quantify the diﬀerence between I+

sand I−

swe deﬁne an asymmetry factor,

αas α= (I+

s− |I−

s|)/(I+

s+|I−

s|)×100 %. The value of αfor the data, shown in Fig. 1d at

30 K, is 17 %.

Switching of JJs from superconducting to resistive state is stochastic and has a ﬁnite dis-

tribution at a ﬁxed temperature [40]. To probe the switching statistics for I+

sand I−

sin our

twisted JJ, we measure 104switching events for both positive and negative bias currents and

compare their distributions. The measurement protocol for switching distribution is discussed

in the methods section. As seen in Fig. 1e, the median value of the distribution also shows asym-

metry, as was seen in a single sweep. In addition, as we tune B, the spread of the distributions

becomes asymmetric – an aspect we discuss later.

BSCCO1

BSCCO2

BAJJ

IJJ

−20 0 20 40

B (μT)

100

150

200

250

Is (μA)

T = 20 K

I+

|I−

−40 −20 0 20 40

B (μT)

−50

−25

asymmetry (%)

T = 20 K

−40 −20 0 20 40

B (μT)

−20

−10

asymmetry (%)

T = 70 K

25 50 75

T (K)

max asymmetry (%)

37.5 40.0 42.5 45.0 47.5 50.0

|Is| (μA)

1000

2000

counts

B = −9.3 μT

I+

s|I−

1000

2000

counts

eT = 70 K

B = 6.9 μT

I+

|I−

Fig. 2: Switching current asymmetry with perpendicular magnetic ﬁeld and temperature

for the 45°twisted BSCCO junction. (a) Cross-sectional schematic of the twisted BSCCO device.

At the junction, current (I) ﬂows along the c-axis of BSCCO. Applied Bis parallel to Ibut perpendic-

ular to the junction plane. An equivalent picture at the junction comprising of IJJs and AJJ is shown

on the right. (b) Variation of switching currents, I+

sand I−

swith Bat 20 K. For each value of B, 100

switching events were recorded with the help of a counter and were averaged to get I+

sand I−

s. The

measurement is done in cryogenic setup 1 with a homemade electromagnet. We have subtracted −5µT

from the data due to an oﬀset value of Bin the measurement setup (see Supplementary Information,

section S13 for details). (c) Asymmetry of switching currents αwith the externally applied magnetic

ﬁeld Bat 20 K. αis calculated from (b), as described in the main text. The two diﬀerent colored line

plots are for diﬀerent sweep directions of B, indicated by the arrows. (d) Variation of calculated αwith

Bat 70 K from the same device. (e) Distributions of switching currents (I+

sand I−

s) at 70 K for two

diﬀerent Bvalues, as indicated in (d) by star and hexagon. The spread of the distributions changes by

the change in sign of B. (f) The maximum value of the asymmetry factor as a function of temperature.

At each temperature, maximum asymmetry is obtained from the Bsweep. The asymmetry persists

below Tcof the junction and increases as the temperature is lowered reaching a value as high as 60 %

at 20 K.

We next study the current asymmetry αat diﬀerent temperatures and with an external

magnetic ﬁeld B, applied perpendicular to the plane of the junction. Fig. 2a shows the cross-

sectional schematic of the device showing the IJJs formed between Cu-O planes and the AJJ,

formed artiﬁcially. As depicted in Fig. 2a, the direction of the current across the AJJ is along

the c-axis, parallel to applied B. Fig. 2b shows the variation of I+

sand I−

swith Bat 20 K.

At each Bvalue, we record 100 switching events with the help of a counter and average it out

to get I+

sand I−

s, which are plotted in Fig. 2b. The measurement protocol is discussed in the

methods section. Importantly, we note a pronounced change of I+

sand I−

swith a very small

magnetic ﬁeld. Variations of I+

sand I−

sshow peaks that are shifted from each other along the

Baxis. The diﬀerence in Bbetween the two peaks corresponds to a few ﬂux quanta through

the junction area. We calculate αfrom this data. Fig. 2c,d show the evolution of calculated

文档加载中……请稍候！
如果长时间未打开，您也可以点击刷新试试。

下载文档到电脑，查找使用更方便

10 玖币 0人已下载

立即下载

摘要：

High-temperatureJosephsondiodeSanatGhosh*1,VilasPatil1,AmitBasu1,Kuldeep1,AchintyaDutta1,DigambarA.Jangade1,RutaKulkarni1,A.Thamizhavel1,JacobF.Steiner2,FelixvonOppen2,andMandarM.Deshmukh11DepartmentofCondensedMatterPhysicsandMaterialsScience,TataInstituteofFundamentalResearch,HomiBhabhaRoad,Mumbai...

展开>> 收起<<

High-temperature Josephson diode Sanat Ghosh1 Vilas Patil1 Amit Basu1 Kuldeep1 Achintya Dutta1 Digambar A. Jangade1 Ruta Kulkarni1 A. Thamizhavel1 Jacob F. Steiner2 Felix von.pdf

共46页,预览5页

还剩页未读，继续阅读

声明：本站为文档C2C交易模式，即用户上传的文档直接被用户下载，本站只是中间服务平台，本站所有文档下载所得的收益归上传人(含作者)所有。玖贝云文库仅提供信息存储空间，仅对用户上传内容的表现方式做保护处理，对上载内容本身不做任何修改或编辑。若文档所含内容侵犯了您的版权或隐私，请立即通知玖贝云文库，我们立即给予删除！

High-temperature Josephson diode Sanat Ghosh1 Vilas Patil1 Amit Basu1 Kuldeep1 Achintya Dutta1 Digambar A. Jangade1 Ruta Kulkarni1 A. Thamizhavel1 Jacob F. Steiner2 Felix von

相关推荐

开通VIP享超值会员特权

作者详情

相关内容

热门标签

举报选择: